Quantization of Charge:
Whatever is the process of charging, it always ends with the transfer of a certain number of electrons from one body to another. An electron is a fundamental particle and it carries a fixed amount of negative charge (e). The SI unit of electronic charge is a coulomb (abbreviated to C). It has been found that one coulomb of charge is equal to the charge carried by 6.25 x 1018 electrons.
|Thus, e = 1/6.25 x 1018 = 1.6 x 10-19 C (Negative)|
All bodies are electrically neutral. They contain equal amounts of positive and negative charges. However, during the charging process, if a body gains a certain number of electrons it becomes a negatively charged body. On the other hand, if the body loses a certain number of electrons, it acquires a positive charge. Since a body gets charged by the transfer of a certain number of electrons, the charge on the body will be
|Q = ±ne|
Where n is the number of electrons transferred and e is the charge on the electron. A charged body, large or small, has a total charge which is some integer multiple of e. This statement is known as the principle of quantization of electric charge.
The following points should be noted in connection with the principle of quantization of charge:
(1) When a body picks up a certain number of electrons, it acquires a negative charge. As electrons are not massless particles, the body mass increases slightly on being charged negatively.
(2) When a body loses a certain number of electrons, it becomes positively charged. The mass of a body decreases slightly on being charged positively.
(3) The charge on a body cannot have any arbitrary value- it has to be an integral multiple of the charge on the electron. Therefore, it is not possible for a body to have a charge, say 7.0 x 10-19 C, since it is not a whole integral multiple of 1.6 x 10-19 C.
(4) On theoretical considerations possibility of particles carrying charges ±(2/3)e and ±(1/3)e has been suggested- these particles are called quarks. These particles have not been detected so far.