The main object of the Industrial Disputes Act is the investigation and settlement of industrial disputes. For this particular purpose, various authorities have been created under the Act. The adjudication of the industrial dispute has at the first instance been kept out of the jurisdiction of the civil courts so that efforts may be made for the settlement of such dispute through some other agencies at the earliest. The industrial disputes are mainly settled through three different modes. They are – (i) conciliation (ii) adjudication, and (iii) arbitration. Different authorities under the Act are works committee, conciliation officer, Board of conciliation, Court of inquiry, Labour Court, Tribunals.

The Industrial Disputes Act, 1947 provides an elaborate and efficient machinery for the peaceful and amicable settlement of the industrial disputes. They include:

1. Works Committees (Sec 3)
2. Conciliation Officers (Sec 4)
3. Board of Conciliation (Sec5)
4. Courts of Enquiry (Sec6)
5. Labour Courts (Sec 7)
6. Tribunals (Sec 7A)
7. National Tribunals (Sec 7B)

Works Committee (Section 3 of the Act):

Negotiation is an important communication process used to resolve conflicts. It is voluntary, non-binding, and a process in which parties control the outcome as well as the procedure. Section 3(1) of the Industrial Disputes Act provides for Works Committee.

Condition for Forming Works Committee:

The industrial establishment in which one hundred or more workmen are employed or have been employed on any day in the preceding twelve months should constitute the works committee. The appropriate Government by general or special order, order the employer to constitute a Works Committee in the prescribed manner.

Constitution of Works Committee:

Works Committee must consist of representatives of employer and workmen engaged in the establishment. The number of members in the committee should be fixed and not more than 20. The number of representatives of workmen on the committee shall not be less than the number of representatives of the employer. The representatives of the workmen shall be chosen in the prescribed manner from among the workmen engaged in the establishment and in consultation with their trade union, if any, registered under the Indian Trade Unions Act, 1926 (16 of 1926). The Central Government or the equivalent authority holds the right to dissolve this committee if they feel it is not constituted as per the guidelines.

Duties of Works Committee:

It shall be the duty of the works committee

• to take measures for securing and preserving amity and good relations between the employer and the workmen;
• to comment upon the matters of their common interest; and
• to endeavour, to compose any material difference of opinion in respect of such matter.

The main purpose of constitution of Works Committee is to develop the sense of partnership between the employer and the workmen. They are normally concerned with the problems arising in the day to day working of the concern. The function of the work committee is to ascertain the grievances of the employees and to arrive at some agreement when the occasion so arises. Works committees are more suitable for the prevention of industrial unrest by unit. Their main purpose is to solve the problem in cordial atmosphere of mutual goodwill and friendship, in the premises of the factory, not as to contesting parties before a conciliation officer. It is comparatively easier to reconcile the differences in the initial stage when neither of the party has taken a very hard stand. From this point of view also, Works Committees plays an effective role in preventing industrial disputes.

The finding of Works Committee is recommendatory or advisory. The final power to decide whether they are to be implemented rests with the employer. The employer is not bound to implement the findings of such committee.

In Kemp & Co. Ltd. v. Workmen, (1955) IILLJ 481 Mad case, the Court observed that the institution of Works Committee has been provided in the rules framed under the Industrial Disputes Act, in order to look after the welfare and interest of the workman,

In the Metal Box Company of India Ltd. v. their Workmen, 1969 AIR 612 case, the Court observed that agreed solutions between the Works Committee and the management are always entitled to great weight and should not be readily disturbed, particularly in matters like classification, grades and scales which are peculiarly within the personal knowledge of the members of the Works Committee.

Dissolution of the Works Committee:

The Central Government or any officer authority to whom the power under Section 39 has been delegated, may, after making necessary enquiry, dissolve any works committee at any time, by an order in writing provided it or he is a satisfied the committee has not been constituted in the accordance with the rules or that not less than 2/3rd of the number of representatives of workmen have without any reasonable justification, failed to attend three consecutive meetings of the committee or that the committee has ceased to function for any other reason, thus defeating the very purpose for which this institution exists in the Industrial law.

Difficulties in Working of Works Committee:

• lack of appreciation on the part of both the parties;
• illiteracy and lack of understanding amongst the workers;
• disinclination of the workers’ representatives to participate in the deliberations of the
  committee; and
• works representatives became unpopular because of their failure in satisfying the high
  expectation of the workers.

Conciliation Officer (Section 4 of the Act):

Conciliation is a process by which discussion between the employers and the employees is kept going through the participation of a conciliator.  Conciliator plays a pivotal role in bringing round the parties involved in the disputes and held in resolving difference by making the parties understand and appreciate the difficulties of each party involved in the dispute in the Industrial field.  As a mediator, his tactful handling of the situation sometimes saves the situation from taking a serious turn.  

Section 4 of the Industrial Disputes Act, provides for Conciliation Officers. This Section corresponds to Section 18-A of the Trade Disputes Act, 1929. According to
this section, the appropriate Government is empowered to appoint, by notification in the Official Gazette, such number of persons as it thinks fit, to be Conciliation Officers, charged with the duty of mediating in and promoting the settlement of industrial disputes. According the sub-section (2), a Conciliation Officer may be appointed for a specified area or for specified industries in a specified area or for one or more specified industries either permanently or for a limited period. Conciliation Officer shall be deemed to be a public servant within the meaning of Section 21 of the Indian Penal Code.

The Conciliation officer is empowered to exercise all quasi-judicial powers of a Civil Court under the Civil Procedure Code, 1908. (CPC). He is or has been a Deputy Chief Labour Commissioner (Central) or Joint Commissioner of the State Labour Department, having a degree in law and at least seven years’ experience in the labour department including three years of experience as Conciliation Officer.

Powers of Conciliation Officer:

Section 11 of the Industrial Dispute Act, 1947, gives provisions for the powers of the conciliation officer.

• Conciliation Officer for the purpose of inquiring into an existing apprehended Industrial Dispute is empowered, after giving the notice to enter the premises occupied by the Industrial establishment.
• Conciliation Officer is also empowered to call for and inspect any document which he may consider relevant to the dispute.
• Conciliation Officer enjoys the same powers as are available to the civil Courts in respect of compelling the parties, to appear and produce all the relevant documents. Thus, the Conciliation officer is empowered to exercise all quasi-judicial powers of a Civil Court under the Civil Procedure Code, 1908. (CPC).
• All Conciliation Officers are Public Servants within the meaning of Section 21 of the Indian Penal Code.

Duties of Conciliation Officers:

Section 12 of the Industrial Disputes Act, gives provisions for duties of the conciliation officer.

• In every industrial dispute, existing or apprehended, the conciliation officer shall hold the conciliation proceedings in prescribed manner.
• The conciliation officer for settling the dispute without delay shall investigate the dispute and may do all such things to make the parties to come fair and amicable settlement of dispute.
• The conciliation officer shall send a report on the settlement of the dispute to the appropriate Government together with a memorandum of the settlement signed by the parties to the dispute.
• If no such settlement is arrived at, the conciliation officer shall as soon as practicable after the close of the investigation, send to the appropriate Government a full report setting forth the steps taken by him for ascertaining the facts and circumstances relating to the dispute, and bringing about a settlement thereof together with a full statement of such facts and circumstances and the reasons on account of which, in his opinion, a settlement could not be arrived at.
• If, on a consideration of the failure report referred above the appropriate Government is satisfied, that there is a case for reference to a Board, Labour Court, Tribunal or National Tribunal it makes such reference. Where the appropriate Government does not make such a reference it shall record and communicate to the parties concerned its reasons thereof
• A report under Sec. 12 shall be submitted within 14 days of the commencement of the conciliation proceedings or within such shorter period as may be fixed by the appropriate Government.

Effects of Conciliation Proceedings:

Under Section 22 of the Act, the Strike and Lockout in a public utility service is prohibited during the conciliation proceedings. If a settlement is arrived, then he is required to send a report along with a copy of a memorandum of settlement signed by the parties to the Appropriate Government. If no settlement is arrived at between the parties the conciliation officer is required to send a full report to the appropriate government, giving all the circumstances relating to the dispute and the steps taken by him to resolve the dispute along with the reasons why the settlement could not be arrived at. Section 33 of the Act provides that during the pendency of Conciliation proceedings, no employer shall after the conditions of service of a workman to his prejudice discharge or punish by dismissal any workman during above proceedings.   

Board of Conciliation (Section 5 of the Act):

Where conciliation fails, board of conciliation takes over. The functions of the Board of Conciliation are the same as those of the conciliation officers. The purpose of constituting boards of Conciliation is to bring about settlement of individual disputes. Section 5 of the Act provides for the constitution of a Board of Conciliation and its powers and duties. A Board of Conciliation is a body of persons, which the appropriate Government may constitute by notification in the Official Gazette for the purpose of promoting the settlement of an industrial dispute. It shall consist of a Chairman and two or four other members, as the appropriate Government may think fit. The Chairman shall be an independent person and the other members shall be persons appointed in equal numbers to represent the parties to the dispute and any person appointed to represent shall be appointed on the recommendation of that party. But if any party fails to make recommendation aforesaid within the prescribed time, the appropriate Government shall appoint such persons as it thinks fit to represent that party.

A Board having a prescribed quorum may act notwithstanding the absence of the Chairman or any of its members or any vacancy in its number. The above-mentioned provisions are subject to the restriction that if the appropriate Government notifies the board that the services of the Chairman or of any other member have ceased to be available, the board shall not act until a new Chairman, or member, as the case may be, has been appointed.

Duties of Board of Conciliation:

Section 13 of the Industrial Disputes Act, 1947, gives provisions related to duties of the Board of Conciliation.

• Where the dispute has been referred to a Board under this Act, it shall be the duty of the Board to endeavour to bring about at settlement of the same and for this purpose the Board shall, in such manner as it thinks fit and without delay, investigate the dispute and all matters affecting the merits and the right settlement thereof and may do all such things as it thinks fit for the purpose of inducing the parties to come to a fair and amicable settlement of the dispute
• If a settlement of dispute or of any of the matters in dispute is arrived at in the course of the conciliation proceedings the Board shall send a report thereof to the appropriate Government together with a memorandum of the settlement signed by the parties to the dispute
• If no such settlement is arrived at, the Board shall as soon as practicable after the close of investigation send to the appropriate Government a full report on the steps taken by the Board for ascertaining the facts and circumstances relating to the dispute and for bringing about a settlement thereof Report shall also contain a full statement of such facts and circumstance and the reasons on account of which, in its opinion a settlement could not be arrived at.
• The board shall submit its report within 2 months of the date on which the dispute was referred to it or within such shorter period as may be fixed by the appropriate Government.

Court of Inquiry (Section 6 of the Act):

Provisions for Court of Inquiry have been made in Section 6 of the Industrial Disputes Act, which lays down that:

The Central Government or the State Government, as the case may be, can appoint a Court of Inquiry. Such appointment is to be notified in the Official Gazette. After notification in Official Gazette, it attains a valid status. Such Court of inquiry is meant to inquire into any matter appearing to be connected with or to an industrial dispute.

A Court may consist of one independent person or such number of independent person as the appropriate Government may think fit and where a Court consists of two or more
members, one of them shall be appointed Chairman. The Court, having the prescribed quorum, may act notwithstanding the absence of the Chairman or any of its members or any vacancy in its number. In absence of Chairman of the Court of inquiry the Court shall not function. If the appropriate Government notifies the Court that the services of the chairman have ceased to be available the Court shall not act until a new Chairman has been appointed.

Duties and Powers of Court of Inquiry:

The powers and duties of these Courts are provided in Sections 11, 14 and 16 to 21 of Chapter IV of the Act. Section 14 of the Industrial Act 1947 prescribes duties of the Court of inquiry are as follows:

• The court of inquiry is to inquire into the matters referred to it under section 10(1) of the Industrial Dispute Act by the appropriate government. It is only those matters which are appearing to be or connected with the industrial dispute that can be referred to it under section 10(1) or under Section 12(5) of the Industrial Dispute Act, 1947.
• The court of inquiry is to make a report to the appropriate government on the basis of an inquiry held by it on the matters referred to it, ordinary within 6 months from the date of commencement of the inquiry. The inquiry made beyond the period of 6 months will not be illegal as the provision is directory in nature.

Effects of Proceedings Before Court of Inquiry:

Unlike the proceedings in the nature of conciliation when there is a legal bar regarding the worker’s right to go on strike, the employer’s right to declare Lockout and dismiss or otherwise punish the workmen under Section 33 of the said Act. The provision of this section 22, 23 and 33 provide that during the pendency of the preceding before the Court, the following rights remain unaffected.

• The workmen’s right to go on strike;
• The Employer’s right to declare Lockout; and
• The employer’s right to dismiss or otherwise punish the workmen under Section 33 of the Act.

Labour Court (Section 7 of the Act):

The appropriate Government may, by notification in the Official Gazette constitute one or more Labour Courts for the adjudication of industrial disputes relating to any matter specified in the second schedule and for performing such other functions as may be assigned to them under this Act. A Labour Court shall consist of one person only to be appointed by the appropriate Government.

The qualifications of a person who can be appointed as Presiding Officer of the Labour Court are mentioned in sub-section (3) of Section 7 as follows :

• he is, or has been, a judge of a High Court; or
• he has, for a period of not less than three years, been a District Judge or an Additional District Judge; or
• he has held any judicial office in India for not less than seven years; or
  (d) he has been the Presiding Officer of a Labour Court constituted under any Provincial Act or State Act for not less than five years.

Jurisdiction of Labour Courts:

The Labour Courts adjudicate the following disputes relating to matters specified in the second schedule:

• The propriety or legality of an order passed by an employer under the standing order.
• The application and interpretation of standing orders.
• Discharge or dismissal of workmen including reinstatement of or grant of relief to workmen wrongfully dismissed.
• Withdrawal of any customary concession or privilege.
• Illegality or otherwise of strike or lock-out. and
• All matters other than those specified in the Third schedule.

Duties of Labour Court:

Section 15 of the Act gives provisions related to the duties of Labour Court. The Labour Court shall hold its proceedings expeditiously and shall as soon as practicable on the conclusion thereof submit its award to the appropriate Government. The functions of the Labour Court as provided in the Act are:

• adjudication of industrial disputes relating to any matter specified in the Second Schedule;
• performing of such other functions as may be assigned to them under this Act.

No time period has been laid down for the completion of proceedings but it is expected that such Courts will hold their proceedings without going into the technicalities of a Civil Court. Labour Court has no power to permit suo motu the management to avail the opportunity of adducing fresh evidence in support of charges). Provisions of Section 137 of the Limitation Act do not apply to reference of dispute to the Labour Court. In case of delays, Court can mould relief by refusing back wages or directing payment of past wages

In Statesman Pvt. Ltd. v. H.R. Deb, AIR 1968 SC 1495 case, the Court observed that the expression “holding a judicial office” in Section 7 (3) (d) signifies more than discharge of judicial functions while holding some other office. The phrase postulates that there is an office and that that office is primarily judicial. Office means a fixed position for performance of duties. The use of same expression in Chapter V of Part VI of the Constitution not in pari materia can have no bearing upon the Industrial Disputes Act and vice versa. The intention of the Legislature really is that men who can be described as independent and with sufficient judicial experience must be selected. The mention of High Court Judges and District Judges earlier in the same section indicates that ordinarily Judicial Officers from the Civil judiciary must be selected at least so long as the separation of judiciary from the executive in the public services is not finally achieved. The appointment of a person from the ranks of Civil judiciary carries with it an assurance, which is unique. The functions of a Labour Court are of great public importance and quasi-Civil in nature. Men of experience on the Civil side of the law are more suitable than Magistrates. Persons employed on multifarious duties and in addition performing some judicial functions, may not truly answer the requirement of Section 7 and it may be open in a quo warranto proceeding to question their appointment on the ground that they do not hold essentially a judicial office because they primarily perform other functions.

In South Indian Bank Ltd. v. A.R. Chacko, AIR 1964 SC 1522 case, the Court observed that Schedule II of the Industrial Disputes Act, 1947 refers specifically to Section 7 of the Act. That section lays down that the appropriate Government may, by notification in the Official Gazette, constitute one or more Labour Courts for the adjudication of industrial disputes relating to any matter specified in the Second Schedule and for performing such other functions as may be assigned to them under this Act. Section 33C (2) in terms assign the determination of the amount of benefit to which the workman is entitled to receive from the employer and which is capable of being computed in terms of money to such Labour Court as may be specified in this behalf by the appropriate Government. The Labour Court, therefore, as specified by the Government, and not the Industrial Tribunal, has jurisdiction to deal with an application made to it under Section 33C (2) of the Act.

In Vijaya Bank v. Shyamal Kumar Lodh, CIVIL APPEAL Nos. 4211 & 4212 OF 2007 case, the Supreme Court held that a Labour Court constituted under the Industrial Disputes Act, 1947, within the local limits of whose jurisdiction the establishment is situated, has jurisdiction to decide any dispute regarding subsistence allowance. The Court observed that here in the present case undisputedly dispute pertains to subsistence allowance and the Labour Court where the workman had brought the action has been constituted under Section 7 of the Industrial Disputes Act, 1947 and further the appellant bank is situated within the local limits of its jurisdiction.

In State of Maharashtra v. Labour Law Practitioners’ Appeal No. 450 of 1979 case, the Bombay High Court held that the Labour Court adjudicates upon disputes which are essentially of a civil nature. The Labour Court’s functions were held as far back as 1968 to be ‘quasi-civil’ in nature. This must apply to the Industrial Court. The Industrial Court has original jurisdiction under the statue. It is also a principal Court, exercises supervision over the Labour Court and hears Appeals from the decisions of the Labour Courts. Accordingly, a member of the Industrial Court may well be said to be a district judge. The Industrial Court and the Labour Court constitute a hierarchy or system of courts, the latter being inferior to the former. The posts of Labour Court judges would, being thus inferior to the post of the district judge, i.e., the Industrial Court Judge, form part of the judicial service.

Tribunals (Section 7A of the Act):

The appropriate Government may be notification in the Official Gazette, constitute one or more tribunals for the adjudication of industrial disputes relating to any matter, whether specified in the Second schedule or the Third schedule. A Tribunal shall consist of one person only to be appointed by the appropriate Government. It shall discharge judicial functions, though it is not a court.   It is the duty of the Tribunal to adjudicate upon any industrial dispute. These Tribunals shall perform such other functions as may be assigned to them under this Act.

The Tribunal shall consist of one person only, whom the State Government shall appoint. Any person having one of the following qualifications may be appointed as the Presiding Officer of the Industrial Tribunal, namely:

• if he is, or has been, a judge of a High Court; or
• if he has for a period of not less than three years, been a District Judge or an Additional District Judge.

It is provided by Section 7-A (4) that the Appropriate Government, if it thinks fit, may appoint two persons as assessors to advise the Tribunal in the proceedings before it. The Government is empowered under Section 7-A of the Act of constitute a Tribunal for a limited time or for any particular case as the case may be.

Jurisdiction of Industrial Tribunals:

Section 7 (A)(l) of the Act deals with the jurisdiction of the industrial tribunal. Industrial tribunals have a wider jurisdiction than a Labour Court. It has jurisdiction over any matter specified in Second or Third Schedule. The following matters are specified under the Third schedule:

• Wages, including the period and mode of payment.
• Compensatory and other allowances.
• Hours of work and rest intervals.
• Leave with wages and holidays.
• Bonus, Profit sharing. Provident Fund and gratuity.
• Shift working otherwise than in accordance with standing orders.
• Classification by grades.
• Rules of discipline.
• Nationalization.
• Retrenchment of workmen and closure of establishment, and
• Any other matter that may be prescribed

Duties of a Tribunal:

The duties of a tribunal are the same as those of a Labour Court

In J.K. Iron and Steel Co., Kanpur v. Iron and Steel Mazdoor Union, AIR 1956 SC 231 case, The Court observed that although these Tribunals are invested with many trappings of a Court but do not have the same status as Courts. The Tribunal can consider the conditions of service of the workmen and can vary them if it is found necessary. The fact that a particular condition exists in other similar concerns is no justification if it could not be justified on its own merits.

National Tribunals (Section 7B of the Act):

The Central Government may by notification in the Official Gazette, constitute one or more National Tribunals for the adjudication of industrial disputes which in the opinion of the Central Government, involve questions of national importance or are of such a nature that industrial establishments situated in more than one state are likely to be interested in, or affected by such disputes. A national tribunal shall consist of one person only to be appointed by the Central Government. The duties of a National Tribunal are the same as those of as Labour Court or an Industrial Tribunal. [Sec.7B (2)]

National Tribunal are constituted by the Central Government through Official Gazette. These Tribunals are constituted for deciding industrial disputes of National importance. These Tribunals are also constituted to solve the industrial disputes of the industries situated in two or more States,

One person as a Presiding Officer is to be appointed by the Central Government. If it is deemed necessary, the Central Government may appoint two or more persons as assessors to advise and assist the Presiding Officer of one-man Tribunal. No person shall be qualified for appointment as Presiding Officer of a National Tribunal unless he is or has been a Judge of a High Court. Section 7-C further provides that such a presiding officer should be an independent person and must not have attained the age of 65 years

Duties of National Tribunals:

Section 15 of the Act, lays down that where an industrial dispute has been referred by the Central Government to a National Tribunal for adjudication, it shall hold its proceedings expeditiously and shall submit the award to the appropriate Government, as soon as possible. Duties of National Tribunals are the same as Labour Court.

Common Provisions:

Section 7C: Disqualification of Presiding Officer:

According to Section 7-C of the Act, no person shall be appointed to, or continue in the office of the Presiding Officer of a Labour Court, Tribunal or National Tribunal, if –

• He is not an independent person; or
• He has attained the age of sixty-five years.

The moment any person suffers from any disqualification, he shall cease to have authority to act in the office concerned.

Section 8: Filling of Vacancies:

If, for any reason a vacancy (other than a temporary absence) occurs in the office of the presiding officer of a Labour Court, Tribunal or National Tribunal or in the office of the chairman or any other member of a Board or Court, then, in the case of a National Tribunal, the Central Government and in any other case, the appropriate Government, shall appoint another person in accordance with the provisions of this Act to fill the vacancy, and the proceeding may be continued before the Labour Court, Tribunal, National Tribunal, Board or Court, as the case may be, from the stage at which the vacancy is filled.

Section 9: Finality of Orders Constituting Boards, etc.:

(1) No order of the appropriate Government or of the Central Government appointing any person as the chairman or any other member of a Board or Court or as the presiding officer of a Labour Court, Tribunal or National Tribunal shall be called in question in any manner; and no act or proceeding before any Board or Court shall be called in question in any manner on the ground merely of the existence of any vacancy in, or defect in the constitution of, such Board or Court.

(2) No settlement arrived at in the course of a conciliation proceeding shall be invalid by reason only of the fact that such settlement was arrived at after the expiry of the period referred to in sub- section (6) of section 12 or sub- section (5) of section 13, as the case may be.

(3) Where the report of any settlement arrived at in the course of conciliation proceeding before a Board is signed by the chairman and all the other members of the Board, no such settlement shall be invalid by reason only of the casual or unforeseen absence of any of the members (including the chairman) of the Board during any stage of the proceeding.

Conclusion 

The Industrial Disputes Act ensures peace and harmony among all the industrial establishments, and if any conflict arises, the provisions in the Industrial Disputes Act helps in solving the issue in a systematic manner in which all the parties are satisfied and every decision made is fair and just. Different authorities under the Act are works committee, conciliation officer, Board of conciliation, Court of inquiry, Labour Court, Tribunals.

The post Authorities Under Industrial Disputes Act appeared first on The Fact Factor.

In this article, we will be studying working of different organizations to check whether the organization comes under the ambit of definition of industry or not.

In Bangalore Water Supply v. A. Rajappa, AIR 1978 SC 548 case, a seven-member Judges’ Bench was constituted to determine the scope of the industry. The triple test working principle was born in the case that is used to check the validity of different establishments. The Triple Test has requisites that are as follows:

1. Systematic Activity
2. Co-operation between the employer and employee
3. Activity concerned with the production of goods and services for the satisfaction of human wants.

Here, the industry will not embody any religious services or other work undertaken out of spiritual bliss. The profit motive stands irrelevant when it comes to any venture. Through the triple test, the focus is concentrated on the functional part emphasizing the employer-employee relations. An establishment that is engaged in philanthropic activities does not cease to become an industry because of it. Thus, if all the above-stated provisions are complied with, then the undertaking can be termed as an ‘industry’ under section 2(j) of the Industrial Disputes Act, 1947.

Notes:

• Absence of profit motive or gainful objective is irrelevant wherever the undertaking is whether in the public, joint, private or other sector.
• The true focus is functional and the decisive test is the nature of the activity with special emphasis on the employer-employee relations.
• If the organization is a trade or business, it does not cease to be one because of philanthropy animating the undertaking.

All organized activity possessing the triple elements in (i) although not trade or business, may still be “industry”, provided the nature of the activity, viz., the employer – employee basis, bears resemblance to what we find in trade or business. This takes into the fold of “industry”, undertaking, callings and services, adventures analogous to the carrying on of trade or business. All features, other than the methodology of carrying on the activity, viz., in organizing the cooperation between employer and employee, may be dissimilar. It does not matter, if on the employment terms, there is analogy.

Application of these guidelines should not stop short of their logical reach by invocation of creeds, cults or inner sense of incongruity or outer sense of motivation for or resultant of the economic operations.  The ideology of the Act being industrial disputes between employer and workmen, the range of this statutory ideology must inform the reach of the statutory definition, nothing less, nothing more. Hence, the Supreme Court observed that professions, clubs, educational institutions. co-operatives, research institutes, charitable projects and other kindred adventures, if they fulfill the triple tests listed above, cannot be exempted from the scope of Section 2(j).

The Supreme Court, in Bangalore Water Supply case laid down the following guidelines for deciding the dominant nature of an undertaking:

• Where a complex of activities, some of which qualify for exemption, others not, involves the employees on the total undertaking. Some of whom are not “workmen” or some departments are not productive of goods and services if isolated, nature of the department will be the true test. The whole undertaking will be “industry” although those who are not “workmen” definition may not be benefit by the status.
• Notwithstanding with previous clause, sovereign functions strictly understood alone qualify for exemption and not the welfare activities or economic adventures undertaken by Government or statutory bodies.
• Even in departments discharging sovereign functions, if there are units which are industries and they are substantially severable, then they can be considered to come within Section 2(j).

Sovereign Functions:

Earlier Sovereign functions were excluded from the ambit of the definition of industry. In Bangalore Water Supply and Sewerage Board v. A Rajiappa (AIR 1978 SC 548) case the Court has clearly said that Sovereign functions which are not involving employee-employer cooperation are excluded.  Sovereign functions strictly understood alone qualify for the exemption, not the welfare activities or economic adventures undertaken by Government or statutory bodies. Even in departments discharging sovereign functions, if there are units which are industries and they are substantially severable then they can be considered to come within Section 2(j).

In Corpn. of City of Nagpur v. Employees (1960 I LLJ 523) case held that If a department of a municipality discharged many functions, some pertaining to “industry” and other non-industrial activities, the predominant function of the department shall be the criterion for the purposes of the Act.

The amendment Act 1982 (which has not been brought into force) has excluded any activity of the Government relating to sovereign functions of the Government, including all activities carried on by the department of the Central Government dealing with defence, research, atomic energy, and space.

Municipal Corporation:

If a department of a municipality discharges many functions some pertaining to industry and others non-industrial, the predominant function of the department shall be the criterion for the purpose of the Act. While in the exercise of delegated legal functions, the Municipal Corporation is not an industry. It is an industry; when its departments render services to the public at large, such as construction, lighting, transport, etc.

By these criteria following activities of Municipal corporation come under the ambit of definition of the industry: Tax, Public Conveyance, Fire Brigade, Lighting, Water Works, City Engineers, Enforcement (Encroachment), Sewerage, Health, Market, Public gardens, Education, Printing Press, Building and General administration.

In D.N. Banerjee v. P. R. Mukherjee, (AIR 1953 SC 58) case, the dispute was between employees working in the sanitary department of Budge Budge Municipalty and Administration. The dispute was regarded as an industrial dispute as both the definition of “industry” and “industrial dispute” were attracted. It was held that the departments those dealing with sanitation and electricity fall within the definition of Industry.

In Corpn. of City of Nagpur v. Employees (1960 I LLJ 523) case the Court held that If a department of a municipality discharged many functions, some pertaining to “industry” and other non-industrial activities, the predominant function of the department shall be the criterion for the purposes of the Act.

Hospitals and Charitable Institutions:

In State of Bombay v. Hospital Mazdoor Sabha (1960 AIR SC 610) case, the Supreme Court held the State is carrying on an ‘undertaking’ within Sec. 2(j) when it runs a group of hospitals for purpose of giving medical relief to the citizens and for helping to impart medical education. The court observed as follows: An activity systematically or habitually undertaken for the production or distribution of goods or for the rendering of material services to the community at large or a part of such community with the help of employees is an ‘undertaking. It is the character of the activity in question which attracts the provisions of Sec. 2 (j), who conducts the activity and whether it is conducted for profit or not, do not make a material difference. Thus, activities that have no commercial implications, such as hospitals carried on with philanthropic motives would be covered by the expression ‘undertaking’. The mere fact that Government runs such activity is immaterial. In case activity is industry if carried on by a private person, it would be so, even if carried on by the Government.

In Management of Safdarjung Hospital v. Kuldip Singh (AIR 1970 SC 1406) case, the decision in State of Bombay v. Hospital Mazdoor Sabha, 1960 AIR SC 610 case is overruled. it was held that a place of treatment of patients run as a department of the government was not an industry because it was a part of the sovereign functions of the government. Charitable hospitals run by Government or even private associations cannot be included in the definition of the industry because they have not embarked upon economic activities analogous to trade or business. If hospitals, nursing home or a dispensary is run as a business in a commercial way, there may be elements of the industry.

In Dhanrajgiri Hospital v. Workmen, AIR 1975 SC 2032 case, the main activity of the hospital was imparting of training in nursing and the beds in the hospital were meant for their practical training. It was held not to be an industry, as it was not carrying on any economic activity in the nature of trade or business.

Therefore, a charitable hospital run by a private trust, offering free services and employing a permanent staff is an industry as there is a systematic activity, a cooperation between employer and employees and rendering of services which satisfies human wants and wishes. Further, the services of employees are hired as in any other business.

In FICCI v. Workmen, AIR 1972 SC 763 case, the Court observed that exemptions to charitable institutions under Section 32(5) of Payment of Bonus Act is not relevant to the construction of Section 2(j), there is an industry in the enterprise, provided the nature of the activity, namely the employer-employee basis bears resemblance to what is found in trade or business. The true focus is functional and the decisive test is the nature of the activity with special emphasis on the employer-employee relations.

Charitable Institutions:

Category – 1:

Those institutions which get profit, but the profits are siphoned (used) for altruistic (unselfish) purposes. The first condition of organized and systematic activity is passed. There is an employee and employer cooperation. Hence the second test is passed. The employee-employer cooperation is for the production of goods and services for human wants. Hence the third test is also passed. To make a profit is the motive. (Actually, it is immaterial). Hence such charitable institutions come under the ambit of definition of “Industry”.

If the institution is run for production and or supply of goods and services with an eye on profit, it is plainly an industry. The fact that the whole or substantial part of profits so earned is diverted for purely charitable purposes does not affect the nature of the economic activity which involves the cooperation of employer and employee and results in the production of goods and services. The workers are not concerned about Where the profit is going. They work and receive wages and are treated like any other workmen in any similar industry. The application of the income for philanthropic purposes, instead of filling individual coffers, makes no difference either to the employees or to the character of the activities.  The motive of the employer in the final disposal of products or profits is immaterial.

Category – 2:

Charitable institutions those make no profit but hire the service of employees as in any other business, but the goods/ services produced, are made available at a low or no cost to the needy and poor. The first condition of organized and systematic activity is passed. There is the hiring of employees as in any other business, there is employee and employer cooperation. Hence the second test is passed. The employee-employer cooperation is for the production of goods and services for human wants. Hence the third test is also passed. To make a profit is not the motive. (Actually, it is immaterial). Hence such charitable institutions come under the ambit of definition of “Industry”.

It is an allotropic modification of the first category. If a socially oriented kind person hires employees and, in cooperation with them, produces and supplies goods or services to the needy and the poor at a low price or free of cost, then he is doing for charity.  As the workmen are concerned, they contribute their labour in return for wages and conditions of service similar to any other similar business. Both pay similar wages under similar working conditions. The charitable approach is towards the users of services and goods and not towards the workmen. The Industrial Dispute Act, 1947 regulates industrial relations between employers and employers,
employers and employee and employee and employee. The Act has nothing to do with the charity. The income-tax Act may give,
some rebates in taxes for such activity. The motive of the employer in the final disposal of products or profits is immaterial.

By this definition, Gandhi Ashrams producing cloth using cotton, charkhas, and handlooms are also termed as “Industry”.

Category – 3:

Charitable institutions that are oriented on a humane mission fulfilled by persons who work, not because they are paid wages, but they work out of their passion for the cause and get job satisfaction. The first condition of organized and systematic activity is passed. Here the second test fails, because there is no employer-employee relation. Everybody is working out of their passion. Hence such charitable institutions do not come under the ambit of definition of “Industry”.

In such cases, there is no concept of an employer or employee. Everybody is working for some cause without expectation of anything in return neither in monetary form nor in physical form.

Legal Firm:

In National Union of Commercial Employees v. M.R. Meher, it was held that a solicitor’s firm is not an industry, although specifically considered, it is organized as an industrial concern. The court held that a person following a liberal profession does not carry on his profession in any intelligible sense with the active co-operation of his employees. Subsidiary work which is purely incidental type and which is intended to assist the solicitor in doing his job has no direct relation to the professional service ultimately rendered by the solicitor. There is, no doubt, a kind of co-operation between the solicitor and his employees, but that co-operation has no direct or immediate relation to the advice or service which the solicitor renders to his client. However this was overruled by Bangalore Water Supply case. wherein it was held that in view of the infrastructure of the offices of professional persons, the contribution to the success of the institution comes not merely from the professional or specialist but from all those whose excellence in their respective spheres makes for total proficiency.

Conclusion:

The law in force presently is the interpretation of the original Section 2(j) as was laid down by Bangalore Water supply Case. The triple test formula is surely pro-labour as it seeks to bring more activities within the ambit of the Industrial Dispute Act 1947. Whenever any dispute arises to determine the validity of an establishment, the provisions of the triple test come into force. If the provisions comply with the work undertaken by the establishment, then it will be an industry under section 2(j) of the Act or else not. There might be times where the establishment is running on profit motive through the rendering of services. Here, the establishment imitates an industry but is not an industry in real. The triple test plays a significant role in the judgements passed by the Court while dealing with uncertain validities of business entities. Whenever any dispute arises, one should consider what type of work the establishment is engage in so that it helps to provide clarity in future.

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To understand the maxim “res ipsa loquitur’ we need to understand the concept of negligence first. To establish negligence, the plaintiff must prove the following:

• Duty: Defendant had a duty to care for the victim.
• Breach of duty: Defendant failed to provide this care.
• Causation: The breach of duty caused the victim’s injuries.
• Damages: The victim was indeed injured.

The plaintiff has the burden of proof to demonstrate these four elements of negligence. Thus, it is the plaintiff’s responsibility to produce necessary evidence against the defendant to have the judgment in his favour. In some cases, mere facts of incidence taken place become prima facie evidence of negligence. The legal doctrine of res ipsa loquitur relieves a plaintiff of his burden of proving any specific act of negligence on the part of the defendant. In a res ipsa loquitur case, the facts warrant an inference of negligence. A judge will determine whether the doctrine of res ipsa loquitur applies.

Elements of ‘res ipsa loquitur’: 

1. The event that caused injury to the plaintiff would not have occurred if someone has not acted negligently. i.e., the incident was of a type that does not generally happen without negligence.
2. The evidence presented rules out all the possibilities of the fault of the plaintiff or third party. Thus, there is no contributory negligence on part of the plaintiff. i.e., it was caused by an instrumentality solely in the defendant’s control and that there are no other plausible explanations.
3. There is a duty of care of the defendant towards the plaintiff which he breached.

If these elements are met, the burden shifts to the defendant to show that he was not negligent

Let us understand with some examples:

1. Small things and tools like hammer may fall out of window injuring somebody walking below the window. It may be negligence or even mischief of somebody. But slipping of small things and tools is not unusual. Hence the doctrine res ipsa loquitur is not applicable.
2. If some heavier thing like a piece of furniture like chair, table falling out of window injuring somebody walking below the window is unusual. It is a clear indication of the negligence. Hence the doctrine res ipsa loquitur is applicable.
3. However, in some cases, there is no direct evidence of negligence. For example, spectators are watching a football game on a college ground. The spectators are sitting on temporarily fabricated benches. The benches collapse, injuring the spectators. The spectators file a personal injury action against the college, which built and maintained the benches. However, the spectators are unable to determine why the benches collapsed. Therefore, the spectators cannot prove that the college was negligent in any particular way. In such a case, a court may invoke the legal doctrine of res ipsa loquitur. If the judge in the collapsing benches case decided to apply the doctrine of res ipsa loquitur, then the spectators would not have to show any specific act of negligence on the part of the college. They would merely have to prove that benches do not ordinarily collapse in the absence of negligence, that the college had exclusive control of the benches, and that the spectators did not contribute to the collapse of the benches by their own negligence. If the spectators proved those three elements, then the college would have to prove that it was not negligent in order to win the case.

Case Laws (Doctrine Applicable):

In Byrne v. Boadle,  2 H. & C. 722, 159 Eng. Rep. 299 (Exch. 1863) case, a man was walking on a sidewalk outside of a flour warehouse when a barrel of flour fell from a warehouse window. The man did not see the barrel fall out of the window, nor could he produce any evidence to indicate how or why the barrel fell from the window of the warehouse. Still, the court thought it apparent that the flour barrel almost certainly came from the flour manufacturer. Moreover, barrels of flour don’t ordinarily fall from warehouse windows in the absence of negligent conduct of the people running that warehouse. The warehouse workers had exclusive control of the barrel that fell out of the window and the plaintiff’s actions did not contribute to his injury. The court allowed the case to proceed because of the nature of the harm-causing event and Defendant’s relationship to it, i.e., as it was Defendant’s responsibility to control the contents of his warehouse, the accident itself is evidence of negligence.

In Read v. S. Pine Elec. Power Asso., 515 So. 2d 916 (Miss. 1987) case, the Court held that under res ipsa loquitur, the defendant’s negligence may be presumed and thus does need not be proven.

In Hayes v. Peters, 645 S.E.2d 846 (N.C. Ct. App. 2007) case, the Court said that under res ipsa loquitur, the finder of fact must be able to infer, through common knowledge and experience, that negligence occurred.

In Municipal Corporation of Delhi v. Subhagwanti, AIR 1966 SC 1750 case, due to the collapse of the Clock Tower situated opposite the Town Hall in the main Bazar of Chandni Chowk, Delhi, a number of persons died. The Clock Tower belonged to the Municipal Corporation of Delhi and was exclusively under its control. It was 80 years’ old but the normal life of the structure of the building, which had fallen, could be 40-45 years, having regard to the kind of mortar used. In these circumstances, the Supreme Court held that the fall of Clock Tower tells its own story in raising an inference of negligence on the part of the defendant. Since the defendants could not prove the absence of negligence on their part, they were held liable. And also, a Clock tower in the heart of the city will need extra care and if it falls and causes injury to several people, the defendants will but obviously be held liable for the same under this principle. In such cases, direct evidence of proving negligence is not important, but the plaintiff has to establish a prima facie case, either by direct or circumstantial evidence of the defendant’s negligence.

In Nihal Kaur v. Director, P.G.I., Chandigarh, August 23,1996 case, where scissors were left in the body of a patient during an operation. Then his condition worsened and he died. Scissors were recovered from the ashes after cremation. Compensation of Rs. 1,20,000 was awarded to the defendants of the deceased.

Case Laws (Doctrine Not Applicable):

In O’Neal v. Burlington N., Inc., 413 N.W.2d 631 (Minn. Ct. App. 1987) where Intoxicated man aged 30 years brought action to recover for injuries sustained when train ran over his left leg while he was sleeping or sitting on the ground next to the railroad tracks with one leg extended across the track.  Appellant contended that he should be considered as irresponsible as a child because he was extremely intoxicated. The Court of Appeals held that man was not within class of persons (child) intended to be protected by statute requiring railroads to build and maintain fences on each side of lines.

In K. Sobha v. Dr. Mrs. Raj Kumari Unithan, 2 November, 1998 case, the plaintiff, aged 35 years, who had an 8-year-old son, approached the defendant, a gynaecologists’, to consult regarding the non-conception of another child. She was advised to test tubing to remove possible obstruction in the fallopian tube. With the plaintiff’s consent, the needful was done by a simple procedure of blowing air through the apparatus into the vagina under controlled pressure. Subsequently, some infection had occurred in the plaintiff’s reproductive system and the same had to be removed. There was no evidence to indicate any negligence on the part of the defendant which could have caused the infection. The cause of infection was, however, unknown. So, under these circumstances, The Kerala High Court held that it was not a case of res ipsa loquitur, as the inference of negligence could not be drawn from the facts of the case.

In R.S.R.T.C. v. Smt. Sayar Bai, AIR 1999 Raj 96 case, there was an accident which was alleged to have occurred due to the mechanical failure of the bus. There was no apparent evidence to indicate the negligence of the bus driver. It was held that the doctrine of res ipsa loquitur could not be applied under the circumstances of the case and the Rajasthan State Road Transport Corporation could be held liable only after its negligence was proved.

Defence Available to Defendant:

Defendants can still rebut the presumption of negligence that res ipsa creates by refuting one of the three elements listed above.

1. The defendant could prove by a preponderance of the evidence that the injury could occur even if reasonable care took place to prevent it. In the flour-barrel example, the defendant can prove an earthquake could shake an item loose and it could fall out of the warehouse window.
2. Prove that the victim contributed to the incident in some way. In the flour-barrel example, if the defendant shows that the plaintiff was standing in an area marked as dangerous it could rebut the presumption of negligence created by res ipsa.
3. The defendant could establish that he did not owe the plaintiff a duty of care under the law, or that the injury did not fall within the scope of the duty owed. For example, if the law only imposes a limited duty on the defendant not to behave recklessly, then res ipsa will not help the plaintiff by creating an inference of negligence since a negligent action would not violate the duty owed to the plaintiff.

Conclusion:

Res ipsa loquitur and negligence per se are both doctrines that assist in proving breach of duty in certain negligence cases. The former allows negligence to be inferred from the circumstances and the latter allows it to be inferred from a violation of law. Both have many applications that allow causes of action to go forward where there is a lack of direct evidence proving negligence.

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Before studying Newton’s laws of motion, we shall understand a very important concept of reference frames in this article.

Motion is a Relative Concept:

Motion is always with respect to the observer. Consider a person A is standing in a train moving in the north direction with a uniform velocity of 5 m/s in a straight line. Let us consider another person B standing on the ground.

Now B as an observer would say that he himself is stationary and the person A is moving in the north direction with a uniform velocity of 5 m/s. Now A as an observer would say that he himself is stationary and the person B is moving in the south direction with a uniform velocity of 5 m/s.

Thus there is a difference in the interpretation of motion of each other it is because their states of motion are different. It is to be noted that both are in the state of uniform motion with respect to earth. Thus we can say that the motion is a relative concept and not the absolute one.

Reference Frame:

It is a system of co-ordinate axes with reference to which position or motion of an object in space is described. The rectangular Cartesian coordinate system of axes is considered as the simplest reference system.

If (x, y, z) are the coordinates of the point in this system of reference, then the position vector of the particle w.r.t. the origin is given by

Let us consider two persons A and B traveling by train with uniform velocity 5 m/s towards right as shown.

There is a third observer C standing on the ground near the track. observer A and B are moving with uniform velocity w.r.t. earth similarly observer C is at rest w.r.t. earth. Hence A, B, C are the inertial frame of reference. We shall ask an opinion of motion of each observer. A will say that he is stationary, B is stationary and C is moving backward with uniform velocity 5 m/s and no force is acting on him. The opinion of B will be similar. But C will say he is stationary and B and C are moving towards the right with uniform velocity 5 m/s. No force acts on them. Then who is correct. Everybody is correct because the motion is always with respect to the state of the observer. Thus Newton’s laws are not violated.

Concept of Inertial Reference Frame:

The reference frame which is at rest or moving with uniform velocity with respect to earth is called inertial reference frame.

Characteristics of Inertial Reference System:

• The reference frames which are at rest or moving with uniform motion with respect to earth are called as inertial reference frames.
• Newton’s laws of motion are applicable in inertial reference frames
• Concept of pseudo force is not required in inertial reference frames.
• A person sitting in a car moving with uniform motion in a straight line is the inertial frame of reference.

Concept of Non-Inertial Reference Frame:

The reference frame which is moving with uniform acceleration w.r.t. earth is called non-inertial reference frame

Characteristics of Non-inertial Reference System:

• The reference frames which are moving with acceleration with respect to earth are called non-inertial reference frames.
• Newton’s laws of motion are not applicable in non-inertial reference frames.
• To apply Newton’s laws of motion in non-inertial reference frames we have to consider the existence of an imaginary force called pseudo force.
• A person sitting in a car negotiating a curve is non-inertial frame of reference.

Distinguish between inertial reference frame and non inertial reference frame.

Concept of Pseudo Force:

Pseudo force is imaginary or hypothetical force whose existence is to be granted in non inertial reference frames so that Newton’s laws of motion are applicable in non inertial reference frame.

Let us consider two persons A and B traveling by train with uniform acceleration 5 ms^-2 towards the right as shown. There is a third observer C standing on the ground near the track. observer A and B are moving with uniform acceleration w.r.t. earth while observer C is at rest w.r.t. earth. Hence A and B are the non-inertial frame of reference, while C is still inertial frame of reference.

We shall ask the opinion of motion of each observer. C will say he is stationary and B and C are moving towards the right with uniform acceleration 5 m/s². Necessary force for acceleration is provided by the engine of the train. Thus he is not violating Newton’s laws of motion. 

A or B will say that he is stationary and C is moving backward with uniform acceleration 5 m/s² and no force is acting on C. It is a contradiction to Newton’s laws of motion because he is saying acceleration is there but no force present to cause it. Thus Newton’s laws of motion are violated in the non inertial reference frame.

To correct A and B the observer in non-inertial reference frame, imaginary or hypothetical force acts on C. This force is called pseudo force.

Examples of Pseudo Forces:

An object revolving in a circle experiences a centrifugal force directed radially outward. This force tends to move the object away from the centre. This centrifugal force is a pseudo force because the circular motion accelerated motion. Thus the object is in acceleration w.r.t. earth. The reference frames which are moving with acceleration with respect to earth are called non-inertial reference frames.

When bus negotiates a curve on the right side, the passengers are pushed on the left side and if the bus negotiates a curve on left side passengers are pushed on the right side. As the bus is negotiating a curve the passengers are in accelerated motion. Thus they constitute the non-inertial reference frame.

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” Luck is what happens when preparation meets opportunity.” – Seneca

Once upon a time, there was a very strong woodcutter. He asked for a job from a timber merchant, and he got it. The pay was really good and so were the work conditions. For that reason, the woodcutter was determined to do his best. His boss gave him an axe and showed him the area where he was supposed to work. The first day, the woodcutter brought down 18 trees. The Boss was very much impressed and said, “Congratulations, Go on that way!”. Very motivated by the words of the boss, the woodcutter tried harder the next day, but he only could bring down 15 trees. The third day he tried even harder, but he only could bring down 10 trees. Day after day he was bringing down less and fewer trees. “I must be losing my strength”, the woodcutter thought to himself. He went to the boss and apologized, saying that he could not understand what was going wrong. “When was the last time you sharpened your axe?” the boss asked. “Sharpen? I had no time to sharpen my axe. I have been very busy trying to cut trees.” the woodcutter replied. The boss said, “You have to take time to sharpen your axe for consistency.”

Our lives are like that. We sometimes get so busy that we don’t take time to sharpen the axe. A great quote, isn’t it? but it’s the opposite of what many people do. When they have a project to work on, many people just work on it directly with little or no preparation. To the contrary, smart people prepare things well in advance and that way they outperform those with little or no preparation. They accomplish the job in less time and with less stress. That’s what I call working smart.

Preparation is essential to work smart.

Initially, it may seem like a waste of time.  But preparation can make the difference between being productive and just being tired.

Preparation helps you find if something is worth doing.

Instead of working on wrong project, it’s wise to check first if something is worth doing. Is it the best use of your time and resources?  Spend time to find out whether or not the  project is feasible. The time saved from not doing the wrong project far outweighs the time spent to research it.

Preparation helps you find the most efficient way to do things. 

Once you decide that a project is worth doing, the next step is finding the most efficient way to do it. If you don’t prepare for the project, you adopt the first method you can think of or the one you are familiar with. But chances are that other methods may save your time and efforts. Do some research to find them. One good way is by watching how the best people in your field work. Find several models and observe the advantages and disadvantages of their methods. Then combine the best methods to create something that suits your project, style and situation.

Preparation makes you ready when opportunity comes. 

When there is no project, you should keep building your skills and knowledge. Keep learning, keep growing, and open your eyes. By this you can see opportunity and can grab it.

Caution:

There is a danger though: you could be over-prepared.

Over preparation may result into delay in taking action. Or it may become a reason for not taking action. Hence do only the preparation that significantly contributes to your project and your personal growth. Prepare well but don’t over-prepare.

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Physics is a science of measurement. In science and engineering, we perform experiments. During experiments, we have to take readings. Thus all these experiments require some measurements to be made. During the production of mechanical products, we have to measure the parts so as to find whether the part is made as per the specifications. Thus measurements are necessary for production and quality control. A measurement is a quantitative description of one or more fundamental properties compared to a standard. To measure length is a very important step during the performance of experiments. Measurement can be done directly or indirectly. In this article, we shall study the use of a micrometer screw gauge to measure length, diameter, etc.

Principle:

A screw gauge works on the principle of a screw in a nut. i.e. in one rotation screw moves forward through a distance equal to the pitch of the screw. The distance between two successive threads of a screw is called its pitch. Or the pitch of a screw may be defined as the distance that the tip of the screw advances when its head is given one complete rotation. The measurements are done actually through a precisely made integrated screw with a pitch of usually 2 threads per millimetre, which means that on completion of one revolution the displacement achieved is 0.5 millimetre. Screw gauges are more precise than Vernier calipers

Construction:

A screw gauge is a device incorporating a calibrated screw that is widely used for the precise measurement of components in the manufacturing of mechanical parts. The body used to hold the anvil and barrel firmly in its place is called a frame, in micrometer screw gauges, thick C-shaped frames are used. It is the fixed part mounted at one end of the frame exactly parallel to the moving spindle which moves towards it. The object whose dimension is to be measured is held between the anvil and the spindle.

The cylindrical part which displaces by rotation of thimble decreasing the distance between itself and anvil until the object being measured becomes stable between the two of them is called the spindle. The stationary part with having a linear scale onto it is called the main scale. It covers the screw mechanism of the screw gauge.

Thimble is the part through which the measuring screw is rotated, this screwing results in the displacement of the spindle and thimble itself. A ratchet is a small device which is used to provide a limited applied force.

A screw gauge has two scales, one rotating scale which can be found on its rotating cylindrical part it is also called a circular scale and the other one can be found on its stationary sleeve which is called the main scale or sleeve scale.

Generally, the least count on the main scale is 0.5 mm. The circular scale is divided into 50 or 100 equal parts.

Least Count:

The minimum length that can be measured using the Vernier calipers is called its least count.

Zero Errors of Micrometer Screw Gauge:

When the anvil and spindle of the screw gauge are made to touch each other, then the zero on the main scale should match with a zero on the circular scale. However due to wear and tear or manufacturing defect the two zeros usually do not coincide with each other, then the vernier is said to have zero error. There are two types of zero errors.

Positive zero error:

If on bringing the anvil and spindle of micrometer screw gauge together, the zero mark of the circular scale is below the main scale line, then the zero error is said to be positive.

To find positive zero error, note the division on the circular scale (C.S.R.) coinciding with the line of the main scale line. Then the positive error is equal to the product of the number of divisions on a circular scale matching with the main scale line and the least count of the micrometer screw gauge. To get the correct reading this error is to be subtracted from the overall reading.

Negative zero error:

If on bringing the anvil and spindle of micrometer screw gauge together, the zero mark of the circular scale is above the main scale line, then the zero error is said to be negative.

To find negative zero error, note the division on the circular scale (C.S.R.) coinciding with the line of the main scale line. Then the negative error is equal to the product of the number of divisions on a circular scale matching with the main scale line and the least count of the micrometer screw gauge. To get the correct reading this error is to be added to the overall reading.

Back-lash Error:

Sometimes the tip of the screw does not move backward for a part of a rotation of the head in the reverse direction, because of the wear and tear of threads. This is called a back-lash error. The back-lash error can be avoided by not rotating the head in the reverse direction once the object is held between the anvil and spindle.

Use of Screw Gauge:

• Hold the object whose dimensions is to be measured between the anvil and spindle of the screw gauge with gentle pressure.
• Note down the main scale reading just before zero of a circular scale. This is called the main scale reading (M.S.R.)
• Note down the number of circular scale division (n) which coincides with the main scale line.  Then circular scale reading, (C.S.R.) = n X Least Count.
• Add the M.S.R. and the C.S.R. to get reading.
• Subtract the zero error with a proper sign from the above reading to get the correct reading.

Example: Let us consider a screw gauge with the least count of 0.01 mm.

The main scale reading is 2.5 mm and circular scale reading is 38. Hence the total reading  = MSR + CSR x LC = 2.5 +38 x 0.01 = 2.5 + 0.38 = 2.88 mm

To Measure Inside Dimensions:

To Measure Depth:

Micron Micrometer Screw Gauge:

In this case, the least count of the main scale is 1mm, the circular scale is divided into 100 parts and each division on the circular scale is divided into 10 parts.

Least count of the main scale 1mm

Least count of circular scale = 1mm/100 = 0.01 mm

Least count of micron micrometer = 0.01/10 = 0.001 mm = 1 x 10^-6 m = 1 micrometre

Micron micrometre screw gauge can be used for measuring the thickness up to 1 micrometre.

Problems on Use of Micrometer Screw Gauge:

Example 01:

The screw of the micrometer screw gauge moves through a distance of 2 mm when it is turned through 4 rotations. Find the pitch of the screw. If the circular scale is divided into 100 equal parts. Find the least count of the micrometer screw gauge.

Solution:

Distance traveled by screw = 2 mm

No. of rotations given = 4

Pitch of screw = Distance traveled by screw / No. of rotations given = 2mm /4 = 0.5 mm

No. of divisions on circular scale = 100

Least count of the micrometer screw gauge = Pitch of screw / No. of circular scale division = 0.5 mm / 100 = 0.005 mm.

Hence the pitch of the screw is 0.5 mm and the least count of the micrometer screw gauge is 0,005 mm.

Example 02:

If the pitch of the micrometer screw gauge screw is 0.1 mm and its circular scale is divided into 100 equal parts. Find the least count of the micrometer screw gauge.

Solution:

Pitch of screw = 0.1 mm

No. of divisions on circular scale = 100

Least count of the micrometer screw gauge = Pitch of screw / No. of circular scale division = 0.1 mm / 100 = 0.001 mm.

Hence the least count of the micrometer screw gauge is 0,001 mm.

Example 03:

If the pitch of the micrometer screw gauge screw is 0.1 mm and its circular scale is divided into 100 equal parts. Find the correct reading for reading as shown. The no-zero error.

Solution:

Pitch of screw = 0.1 cm = 1 mm

No. of divisions on circular scale = 100

Least count of the micrometer screw gauge = Pitch of screw / No. of circular scale division = 1 mm / 100 = 0.01 mm.

Main scale reading = 4.5 mm

Circular scale reading = 28

Shown reading = M.S.R. + C.S.R. x Least Count = 4.5 + 28 x 0.01 = 4.5 + 0.28 = 4.78 mm

Corrected reading = shown reading – zero error with proper sign = 4.78 – 0 = 4.78 mm

Hence the corrected reading is 4.78 mm.

Example 04:

When a screw gauge with a least count 0.01 mm is used to measure the diameter of a wire, the reading on the sleeve is found to be 0.5 mm and the reading on the thimble is found to be 27 divisions. What is the correct diameter of the wire if the zero error for the gauge is +0.005 cm?

Solution:

Least count of the micrometer screw gauge = 0.01 mm.

Main scale reading = 0.5 mm

Circular scale reading = 27

Shown reading = M.S.R. + C.S.R. x Least Count = 0.5 + 27 x 0.01 = 0.5 + 0.27 = 0.77 mm

Zero error = +0.005 cm = 0.05 mm

Corrected reading = shown reading – zero error with proper sign = 0.77 – 0.o5 = 0.728 mm

Hence correct diameter of wire is 0.72 mm.

Example 05:

When a screw gauge with a least count 0.01 mm is used to measure the diameter of a rod, the reading on the sleeve is found to be 1.6 cm and the reading on the thimble is found to be 48 divisions. What is the correct diameter of the rod if the zero error for the gauge is – 0.003 cm?

Solution:

Least count of the micrometer screw gauge = 0.01 mm.

Main scale reading = 1.6 cm = 16 mm

Circular scale reading = 48

Shown reading = M.S.R. + C.S.R. x Least Count = 16 + 48 x 0.01 = 16 + 0.48 = 16.48 mm = 1.648 cm

Zero error = – 0.003 cm

Corrected reading = shown reading – zero error with proper sign = 1.648 + 0.o03 = 1.651 cm

Hence correct diameter of wire is 1.651 cm.

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Physics is a science of measurement. In science and engineering, we perform experiments. During experiments, we have to take readings. Thus all these experiments require some measurements to be made. During the production of mechanical products, we have to measure the parts so as to find whether the part is made as per the specifications. Thus measurements are necessary for production and quality control. A measurement is a quantitative description of one or more fundamental properties compared to a standard. To measure length is a very important step during the performance of experiments. Measurement can be done directly or indirectly. For direct methods metre scale, vernier calipers, micrometer screw gauges are used. In this article, we shall study the use of Vernier Callipers to measure length, diameter, etc.

Construction:

Vernier calipers is a device is used to measure the internal and external diameter of a tube, the external diameter of a sphere, depth of a vessel, the diameter of thick wires and cylinders.

Typical Vernier calipers consist of a steel strip which is generally marked in centimetre and millimetre along its lower edge this is a fixed scale called the main scale. The end of the main scale is provided with a fixed jaw forming external jaw on the lower side and internal jaw on the upper side. A sliding frame with graduation on the lower side slides over the main scale. This sliding scale is called the Vernier scale. The inside end of a Vernier scale is provided with a fixed jaw forming external jaw on the lower side and internal jaw on the upper side.

Generally, the Vernier scale is provided with N divisions matching with (N – 1) divisions of the main scale.

Least Count of Vernier Scale:

The minimum length that can be measured using the Vernier calipers is called its least count.

Zero Errors of Vernier Calipers:

When the two jaws of Vernier calipers are made to touch each other, then the zero on the main scale should match with a zero on the Vernier scale. However due to wear and tear or manufacturing defect the two zeros usually do not coincide with each other, then the Vernier is said to have zero error. There are two types of zero errors.

Positive zero error:

If on bringing both the jaws together, the zero mark of the Vernier scale is on the right side of a zero mark of the main scale, then the zero error is said to be positive.

To find positive zero error, note the division on the Vernier scale (V.S.R.) coinciding with the division on the main scale. Then the positive error is equal to the product of the number of division on Vernier scale matching with main scale division and the least count of the Vernier. To get correct reading this error is to be subtracted from the overall reading.

Negative zero error:

If on bringing both the jaws together, the zero mark of the Vernier scale is on the left side of a zero mark of the main scale, then the zero error is said to be negative.

To find a negative zero error, note the division on the Vernier scale (V.S.R.) coinciding with the division on the main scale. Subtract this number from a total number of divisions on the Vernier scale to obtain V.S.R. Then the negative error is equal to the product of V.S.R. and the least count of the Vernier. To get correct reading this error is to be added to the overall reading.

Use of Vernier Calipers:

• Hold the object whose dimensions is to be measured in the jaws of the calipers with gentle pressure.
• Note down the main scale reading just before zero of vernier calipers. This is called the main scale reading (M.S.R.)
• Note down the number of vernier scale division (n) which coincides with any division of the main scale.  Then vernier scale reading, (V.S.R.) = n X Least Count.
• Add the M.S.R. and the V.S.R. to get reading.
• Subtract the zero error with a proper sign from above reading to get the correct reading.

Uses of Different Parts of Vernier Calipers:

• The outside jaw is used to measure outside dimensions like the length of a rod, the external diameter of the sphere or cylinder.
• The inside jaw is used to measure inside dimensions like the internal diameter of ring or hollow cylinder or pipe
• The strip is used to measure the depth of a beaker or bottle.
• The main scale is used to measure the length of an object correct up to 1 mm.
• Vernier scale is used to measure the length of an object correct up to 0.1 mm

Dial Vernier Calipers (Direct Reading)

Digital Vernier Calipers (Direct Reading)

Problems on Use of Vernier Calipers:

Example 01:

The main scale of a Vernier scale has the least count of 0.5 mm. If 20 divisions of this scale are divided into 25 equal parts of the Vernier scale, what is the least count of the Vernier caliper?

Solution:

1 M.S.D. = 0.5 mm

25 V.S.D. = 20 M.S.D.

Thus,    1 V.S.D. = 20/25 M.S.D. = 0.8 M.S.D. = 0.8 x 0.5 mm = 0.4 mm

Now, Least Count of Vernier Caliper = 1 M.S.D. – 1.V.S.D. = 0.5 mm – 0.4 mm = 0.1 mm

Hence least count of Vernier caliper is 0.1 mm

Example 02:

On Vernier calipers, one centimetre of the main scale is divided into 10 equal parts. If 10 divisions of the Vernier scale coincide with 9 divisions of the main scale, then what will be the least count of the Vernier caliper?

Solution:

1 M.S.D.    =   cm = 0.1 cm

10 V.S.D.   = 9 M.S.D.

Thus,    1 V.S.D = 9/10 M.S.D.   =   0.9 M.S.D. = 0.9 x 0.1 cm = 0.09 cm

Now, Least Count of Vernier Caliper = 1 M.S.D. – 1.V.S.D.    =    0.1 cm – 0.09 cm = 0.01 cm

Hence least count of Vernier caliper is 0.01 cm

Example 03:

On Vernier calipers, one centimetre of the main scale is divided into 20 equal parts. If the number of divisions on the Vernier scale is 25. Find the least count of the Vernier caliper. In a measurement of the length of an object, the main scale reading lies between 2.35 cm and 2.40 cm. Vernier scale reading is 6.  Find the length of the object.

Solution:

On main scale 1 cm is divided into 20 equal parts. Hence 1 M.S.D.    =  1/20 cm = 0.05 cm.

Now least count = (1/No. of divisions of Vernier scale) x M.S.D. = (1/25) x 0.05 cm = 0.002 cm.

Reading = Main scale reading + Vernier scale reading x Least Count Reading = 2.35 + 6 x 0.002 =    2.35 + 0.012 = 2.362 cm

Hence the length of the object is 2.362 cm

Example 04:

On Vernier calipers, one centimetre of the main scale is divided into 20 equal parts. If the number of divisions on the Vernier scale is 25. Find the least count of the Vernier caliper. In a measurement of the length of an object, the main scale reading lies between 2.75 cm and 2.80 cm. Vernier scale reading is 9.  The zero error is + 0.024 cm. Find the length of the object.

Solution:

On main scale 1 cm is divided into 20 equal parts. Hence 1 M.S.D.    =  1/20 cm = 0.05 cm.

Now least count = (1/No. of divisions of vernier scale) x M.S.D. = (1/25) x 0.05 cm = 0.002 cm.

Reading = Main scale reading + Vernier scale reading x Least Count – Zero error Reading

= 2.75 + 9 x 0.002  – (+ 0.024)   =    2.75 + 0.018 – 0.024 = 2.744 cm

Hence the length of the object is 2.744 cm

Example 05:

On Vernier calipers, one centimetre of the main scale is divided into 10 equal parts. If the number of divisions on the Vernier scale are 10. Find the least count of the Vernier caliper.  In a measurement of the length of an object, the main scale reading lies between 5.6 cm and 5.7 cm. Vernier scale reading is 4.  The zero error is – 0.02 cm. Find the length of the object.

Solution:

On main scale 1 cm is divided into 10 equal parts. Hence 1 M.S.D.    =  1/10 cm = 0.1 cm.

Now least count = (1/No. of divisions of vernier scale) x M.S.D. = (1/10) x 0.1 cm = 0.01 cm.

Reading = Main scale reading + Vernier scale reading Least Count – Zero error Reading

= 5.6 + 4 x 0.01  – (- 0.02)  =   5.6 +  0.04  +0.02  = 5.66 cm

Hence the length of the object is 5.66 cm

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Physics is a science of measurement. In science and engineering, we perform experiments. During experiments, we have to take readings. Thus all these experiments require some measurements to be made. During the production of mechanical products, we have to measure the parts so as to find whether the part is made as per the specifications. Thus measurements are necessary for production and quality control. A measurement is a quantitative description of one or more fundamental properties compared to a standard. To measure length is a very important step during the performance of experiments. Measurement can be done directly or indirectly. For direct methods metre scale, vernier callipers, micrometre screw gauges are used. In this article, we shall study the use of metre scale to measure length, diameter, etc.

When measurements are taken directly using tools, instruments, or other calibrated measuring devices, they are called direct measurements. e.g. Measurement of the length of a table by metre scale. When the measurement must be done through a formula or other calculations, the measurement is called indirect measurement. e.g. Measurement of the radius of the Earth.

Old Methods of Measurement of a Length

To measure lengths units used were a finger, palm, span, cubit, foot, yard, fathom, furlong etc.  The length of an inch was originally decided by Edward-II of England in the early 1300s as the length of three grains of barley laid end to end. Inch was divided into three parts called barley.

Measurement of Length:

The length is a fundamental quantity, it is used to measure a distance between two points in space. S.I. unit of length is a metre (m) and c.g.s. unit of length is centimetre (cm). Other practical units of measurement of length are micrometre (mm), millimetre (mm), kilometre (km), Angstrom (A°) etc.

Length of accessible objects can be measured directly using a metre scale, vernier callipers, micrometre screw gauge, measuring tapes, travelling microscopes etc. Length of non-accessible objects is measured indirectly.

Metre Scale:

one metre is divided into 100 equal parts, each part is called centimetre. Each centimetre is divided into 10 equal parts, each part is called millimetre. Engineering metre scale has centimetres marked on one edge and inches marked on another edge. Centimetres have decimal divisions while inches have fractional divisions. metre scale may have bevelled edges to avoid errors due to parallax.

Least count is the smallest measurement that can be taken accurately with an instrument or device. The least count of a metre scale is 1 mm or 0.1 cm.

Linear Measurements (Direct Method):

Place the metre scale along the object so that the ‘0’ mark on the metre scale coincides with one end of the object and reading at the other end of the scale indicates the length of the object. To avoid wear and tear off the end of the scale, sometimes the scale is placed along the object and readings at the ends of the object are taken. The length of the object is obtained by subtracting higher reading from lower reading.

The eye must be kept vertically above the end of the object so that the corresponding graduation can be read clearly. If the eye is not kept exactly vertically above the end of the object, it leads into error called parallax error.

In case, the end of the object lies between the two small divisions of the scale, the correct length is reported by noting the marking nearer to the end of the object. Limitation of metre scale is that it cannot measure the length of an object smaller than 1 mm or 0.1 cm.

Measurement of Length of a Curve

Thread Ruler Method (Direct Method):

In this case, a thread is laid along the curve. Then the length of the thread is measured using a metre scale.

Divider Ruler Method (Direct Method):

In this method, the curve is divided into small straight segments. Length of each such segment is measured using divider and scale. Then the total length of the curve can be obtained by adding lengths of all individual segments.

External diameter of cylinder or sphere

Blocks Ruler Method (Direct Method):

A cylinder or sphere whose external diameter is to be measured is placed between two blocks. The reading on the scale corresponding to the inner edge is x cm while that corresponding to the outer edge is y cm. Then the diameter is the absolute value of (x-y) cm.

Caliper Ruler Method (Direct Method):

To measure the external diameter of sphere or cylinder, an external calliper is used. In this method, the cylinder or sphere whose external diameter is to be measured is placed between two jaws of the calliper. The position of the calliper is fixed by tightening the screw. The distance between the jaws gives the external diameter of the cylinder or the sphere.

External Diameter of Cylinder: (Indirect Method):

A known number of turns (N) of a thin wire are wound on a cylinder whose diameter is to be measured. Then the wire is unwounded and straightened. Then its length is measured. The diameter of the rod can be obtained by the formula

To measure the internal diameter of the cylinder, an internal calliper is used.

External Diameter of Thin Wire: (Indirect Method):

A known number of turns of the wire whose diameter is to be measured are wound on a scale or on a rod of uniform diameter. The length of turns on the scale or the rod is measured. The diameter of the wire is calculated by dividing the length of turns by the number of turns.

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In this article, we shall study graphical representation of S.H.M. i.e. variation in displacement, velocity, and acceleration with time for a body performing S.H.M. starting from a) the mean position and b) from the extreme position.

Graphical Representation of Linear S.H.M. of a Particle Starting from Mean Position:

The general equation for the displacement of a particle performing linear S.H.M. at any instant ‘t’ is given by

x = a  sin (ωt + α )

Where a = amplitude of S.H.M., ω = angular speed of S.H.M.,

α = Initial phase of S.H.M.

As particle is starting from mean position, α = 0

x  =  a  sin ωt   …….. (1)

Velocity of particle performing S.H.M.can be obtained by differentiating above expression

v = dx/dt = a cos ωt . ω = ωa cos ωt

v =  ωa cos ωt   …….. (2)

Acceleration of particle performing S.H.M. can be obtained by differentiating above expression

f = dv/dt = ωa (-sin ωt)  ω

f = dv/dt = – ω²a sin ωt    …….. (3)

From equation (1) and (3) we have

f = dv/dt = – ω²x    …….. (4)

Using equations (1), (2) and (4) and knowing ω = 2π/T we prepare following table

The graphs of displacement, velocity and acceleration versus time are as follows:

Graphical Representation of Linear S.H.M. of a Particle Starting from Extreme Position:

The general equation for displacement of a particle performing linear S.H.M. at any instant ‘t’ is given by

x = a  sin (ωt + α )

Where a = amplitude of S.H.M., ω = angular speed of S.H.M., α = Initial phase of S.H.M.

As particle is starting from mean position, α = π/2

x = a  sin (ωt + π/2 )

x  =  a  cos ωt   …….. (1)

Velocity of particle performing S.H.M.can be obtained by differentiating above expression

v = dx/dt = a (- sin ωt) . ω = – ωa sin ωt

v =  – ωa sin ωt …….. (2)

Acceleration of particle performing S.H.M. can be obtained by differentiating above expression

f = dv/dt = – ωa (cos ωt)  ω

f = dv/dt = – ω²a cos ωt    …….. (3)

From equation (1) and (3) we have

f = dv/dt = – ω²x    …….. (4)

Using equations (1), (2) and (4) and knowing ω = 2π/T we prepare following table

The graphs of displacement, velocity and acceleration versus time are as follows:

Conclusions:

• Graphs are drawn for displacement, velocity and acceleration against time and curves are obtained as shown.  As the curves have the shape same as the sine curve, the curves are called as harmonic curves.
• From the graph, we can conclude that the displacement, velocity, and acceleration are the periodic functions of time.
• From the graph, we can see that velocity is 90° (π/2 radians) out of phase with displacement, whereas acceleration is 180° (π radians) out of phase with displacement. Similarly, acceleration is 90° (π/2 radians) out of phase with velocity.
• The velocity leads the displacement by a phase difference of π/2 radians.
• The acceleration lags behind displacement by a phase of π radians.
• The displacement and acceleration are maximum at the extreme position while velocity is minimum at the same position. Similarly, the displacement and acceleration are minimum at the mean position while velocity is maximum at the same position.
• All curves repeat after a phase of 2π radians.

Previous Particle: Numerical Problems on Velocity and Acceleration of a Body Performing S.H.M.

Next Topic: Energy of Particle Performing S.H.M.

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In this article, we shall study the COulomb’s law of electrostatics, its explanation, uses, and limitations.

Coulomb’s Law of Electrostatics:

Statement:

The force of attraction or repulsion between two electric point charges is directly proportional to the product of the magnitude of the charges and inversely proportional to the square of the distance between the two charges. The force acts along the line joining the two charges.

Explanation:

Let q₁ and q₂ be the two-point charges separated by distance ‘r’ in a medium with dielectric constant ‘k’  Then,

F  ∝ q₁ . q₂   ………..  (1)

F  ∝ 1/r²…………(2)

From statement (1) & (2) we get

Where F   = force between the two charges,

∈_o  = electrical permittivity of free space. = 8.8542 × 10^-12 C² N^-1m^-2 or F m^-1.

k  = dielectric constant of the medium.

This expression is called a mathematical statement of Coulomb’s Law.

The value of the constant

Hence the equation of Coulomb’s law can be written as

In cgs system the value of 1/4πε_o = 1

Coulomb’s force is not affected by the presence or absence of other charges.

Coulomb’s Law in a Vector Form:

Where  F ₂₁ = Force on the second charge due to the first charge.

r ₁₂ = Unit vector from the first charge due to the second charge

Where  F ₁₂ = Force on the second charge due to the first charge.

r ₂₁ = Unit vector from the first charge due to the second charge

as unit vector r ₁₂ = – unit vector r ₂₁

 F ₂₁ = – F ₁₂

Thus the forces are equal but oppositely directed.

If we consider the signs of the charges (positive and negative) then the vector form of coulomb’s law can be written as

Coulomb’s Law in Terms of Position Vector:

Let r₁ and r₂  be the position vectors of charges q₁ and q₂ situated at point A and B respectively w.r.t. origin O.

By triangle law of vector addition

By Coulomb’s law, the force on charge q₁ due to charge q₂ is given by

This is the vector form of Coulomb’s law in terms of position vectors of charges.

Limitations of Coulomb’s law:

• Coulomb’s law is applicable to point charges only and is not applicable to extended bodies.
• It can be applied to extended bodies by assuming them to be point charges but the distance between them should be sufficiently large,
• The law holds good only for stationary charges.
• Coulomb’s law is verified for distances from 10^-15 m to several kilometres. We are not sure about its validity for a distance less than 10^-15 m (nuclear dimensions).

Notes:

• The charges possessing the same nature of charge are called like charges. Like charges either all positive or all negative. Like charges always repel each other.
• The charges possessing opposite nature of charge are called, unlike charges. Unlike charges always repel each other.

Dimensions of Electrical Permittivity:

Hence dimensions of universal electrical permittivity are [L^-3M^-1T⁴I²]

Units of charge:

Coulomb: SI unit of charge is coulomb.

Definition of Coulomb (Using Coulomb’s Law):

By Coulomb’s Law

If q₁ = q₂ = q, r = 1 m and F = 9 × 10⁹ N, k =1, then

q² = 1 and q = ± 1 C

The charge of 1 coulomb is that charge which, when placed in free space at a distance of 1 metre from an equal and similar charge, repels it with a force of  9 × 10⁹ N

Definition of Coulomb (Using Electric Current):

The electric current flowing through any section of a conductor is given by

I = q/t

Where q   =   electric charge flowing through any section of the conductor

t    =   time for which the charge is flowing

q = I × t

unit of charge = unit of a current × unit of time

1 coulomb = 1 ampere × 1 second

Hence a charge of 1 coulomb is defined as the quantity of a charge which flows per second through any cross-section of a conductor when there is a steady current of 1 ampere in the conductor.

statcoulomb or electrostatic unit (esu) of charge:

statcoulomb or esu of charge is cgs unit of charge. In cgs system the value of 1/4πε_o = 1

If q₁ = q₂ = q, r = 1 cm and F = 1 dyne, then

q² = 1 and q = ± 1 C

Hence one statcoulomb of a charge is that charge which, when placed in free space at a distance of 1 cm from an equal and similar charge, repels it with a force of 1 dyne. In cgs system unit of electromagnetic charge is abcoulomb or emu of charge.

Conversions:

Note:

These definitions are for convenience and not standard. When defining S.I. Unit coulomb in standard conditions help of the magnetic effect of electric current is considered.

Dielectric Constant of Medium:

Definition:

The ratio of the electrical permittivity of the medium to the electrical permittivity of free space is called the dielectric constant of the medium.

k = ∈ / ∈_o 

The dielectric constant of e medium is denoted by letter ‘k’ or ‘∈_r‘. As it is a pure ratio it has no unit. For air or vacuum k = 1 for any other medium k > 1.

Let q₁ and q₂ be the two point charges separated by distance ‘r’ in a medium in a vacuum, and then the same charges separated by the same distance in a medium with dielectric constant ‘∈_r‘.

Thus the dielectric constant or relative permittivity of a medium can be defined as the ratio of the electrostatic force between two charges separated by a certain distance in vacuum to the electrostatic force between the same two charges separated by the same distance in the medium. The presence of dielectric reduces electrostatic force between two charges which implies that the electrostatic force between two charges is maximum in a vacuum.

Comparison Between Electrostatic Force and Gravitational Force:

Points of Similarity:

• Both the forces obey the inverse square law of distances.
• Work done by both the forces does not depend on the path followed. Hence both the forces are conservative forces.
• Both the forces act along the line joining the centres of interacting bodies. Hence both the forces are central forces.
• Both the forces operate even in the vacuum.

Point of Dissimilarity:

• Gravitational force is always that of attraction while the electrostatic force may be attractive or repulsive depending upon the nature of interacting charges.
• Gravitational force is unaffected by the intervening medium. The electrostatic force depends on the dielectric constant of the intervening medium.
• The electrostatic force is very much stronger than the gravitational force. Let us consider an electron-proton system in an atom. The electrostatic force F_e and gravitational force F_g between them are given by

• We can see that the electrostatic force is 1039 times stronger than the gravitational force. But gravitational force plays a more significant role than the electrostatic force because most of the bodies in the universe are electrically neutral. Similarly, due to the attractive or repulsive nature of electrostatic force, they can cancel each other while gravitational force is only of attraction hence there is no question of cancellation of the gravitational force. Thus gravitational force is weak but has the dominating effect.
• Electrostatic forces are weaker than nuclear forces.

The principle of Superposition of Forces:

• This principle is used for calculation of net force acting on an individual charge due to other when more than two charges are interacting with each other.
• When a number of charges are interacting, the total force on a given charge is the vector sum of individual forces exerted on a given charge by all other charges.
• Let us consider a  system of point charges q1, q2, q3, q4, ……..qn.  Let F12, F13, F14, F15, ……..F1n be the forces acting on charge q1 due to charges q₂, q₃, q₄, ……..q_n respectively.
•  Then according to the principle of superposition of forces, the force acting on charge q₁ is given by

 F₁ =  F₁₂ + F₁₃ + F₁₄ +  ……+ F_1n

By vector representation

Applying the same logic to all such pairs we have

• The same procedure can be adopted for finding the force on any other charge due to the remaining charges.

Numerical Problems:

Example – 01:

The distance between electron and proton in a hydrogen atom is 5.3 × 10^-11 m. What is the magnitude of the electric force between them?

Given: Distance between proton and electron = r =  5.3 × 10^-11 m, The magnitude of the charge on proton = q₁ = 1.6 × 10^-19 C, Magnitude of the charge on electron = q₂ = 1.6 × 10^-19 C.

To find: Force =?

Solution:

By Coulomb’s law

Ans: The electric force between electron and proton is 8.202 × 10^-8 N.

Example – 02:

Two charges of magnitudes 1 μC and 2 μC are separated by a medium of dielectric constant 2. What is the magnitude of the electric force between them?

Given: Distance between proton and electron = r =  10 cm = 0.1 m, The magnitude of the first charge = q₁ = 1 μC = 1 × 10^-6 C, Magnitude of the charge on second charge = q₂ = 2 μC = 2 × 10^-6 C, dielectric constant of medium = k = 2.

To find: Force =?

Solution:

By Coulomb’s law

Ans: The electric force between the charges is 0.9 N.

Example – 03:

Two small spheres are charged positively. The combined charge being 5.0 x 10-5 C. If each sphere is repelled from other by a force of 1.0 N when they are 2.0 m apart. How is the total charge distributed between two spheres?

Given: Distance between two charges = r =  2.0 m, Sum of the cahrges = 5.0 × 10^-5 C =  50 × 10^-6 C, Let , The magnitude of the first charge = q₁ = q μC = q × 10^-6 C, Magnitude of the other charge = q₂ =(50 – q)  × 10^-6 C, dielectric constant of medium = k = 1. Force = F = 1.0 N

To find: charges = ?

Solution:

By Coulomb’s law

∴ q₁= 38.43 m C = 38.43 × 10^-6 C = 3.84 × 10^-5 C

∴ q₂= 11.57 m C = 11.57 × 10^-6 C = 1.16 × 10^-5 C

Ans: The distribution of charge is 3.84 × 10^-5 C and 1.16 × 10^-5 C

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