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| Basic Properties of Electric Charges |
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| If a system consists of two point charges q1 and q2, then the total charge of the system is got by adding q1 and q2. Thus, the charge add up like real numbers (scalars). When we add charges, one should take care of its sign. |
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| Just like energy and mass can be conserved, the electric charges can also be
conserved. |
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| The law of conservation states that the total charge of an isolated system remains constant that is, Charges can neither be created nor destroyed. |
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| The principle of quantisation of electric charge states that "in nature there is a smallest amount of charge and all other charges are integral multiples of this smallest unit ". |
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| That is, if e is the minimum charge then the total charge on the body is equal to ne where n is an integer. |
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| This fact that electric charge is quantised was first suggested by experimental laws of electrolysis discovered by Faraday and then by Millikan. In chemical electricity and magnetism, quantisation of charge is completely ignored because the quantum of charge e is very small. In microscopic level, where the charges involved are of the order of few powers of tens or hundreds of e, quantisation of charge cannot be ignored. |
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| Note: |
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| (i) the magnitude of the smallest unit of charge is 1.6x10-19 C |
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| (iii) a charged body cannot possess fractional charge. |
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| (iv) the total charge on a body is equal to the algebraic sum of the individual charges present in the body. |
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| (v) a body is electrically neutral if it has equal number of positive and negative charges. |
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| (vi) the charge is quantised, which means that the charge exists in the form of discrete packets. |
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