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Discuss the basic properties of electric charges. |
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Answer» SOLUTION :(i) Electric charge : Most objects in the universe are made of atoms which in turn are made up of protons neutrons and electrons. These particles have mass an inherent property of particles . Similarly the electric charge is another intrinsic and fundamental property of particles . The SI unit of charge is coulomb . (ii) Conservation of charges : Benjamin Franklin argued that when one object is rubbed with another object charges get transferred from one to the other . Before rubbing both objects are electrically neutral and rubbing simply transfers the charges form one object to the other . (For examplewhen a glass rod is rubbed against silk cloth some negative charge are transferred from glass to silk . As a result the glass rod is positively charged and silk cloth becomes negatively charged ) . From these observations he concluded that charges are neither created or nor destroyed but can only be transferred from one object to other . This is called conservation of total charges and is one of the fundamental conservation laws in physics . It is stated more generally in the following way . The total electric charge in the universe is constant and charge can neither be created nor be destroyed . In any physical process the net change in charge will always be zero. (iii) Quantisation of charges : The charge q on any object is equal to an integral multiple of this fundamental unit of charge e. q=ne Here n is any integer `(0,pm1,pm2,PM3,PM .... ).` This is called quantisation of electric charge . Robert Millikan in his famous experiment found that the value of e `= 1.6xx10^(-19)C.` The charge of an electron is `-1.6xx10^(-19)C` and the charge of the proton is `+1.6xx10^(-19)C` . When a glass rod is rubbed with silk cloth the number of charges transferred is usually very large typically of the order of `10^(10)` .So the charge quantisation is not appreciable at the macroscopic level . Hence the charges are treated to be continuous ( not discrete ) . But at the microscopic level , quantisation of charge PLAYS a vital role. |
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