Coulomb ’ s Law
1 . Additivity of charges :
o Point charges are scalars and can be added algebraically . If q 1 , q 2 , q 3 , … q n , are point charges , the total charge q tot = q 1 + q 2 + q 3 + q n
o Charges have no direction but can be positive or negative . 2 . Conservation of charges : o
o
Total charge in an isolated system is always conserved . When there are many bodies in an isolated system , the charges get transferred from one body to another but the net charge of the system remains same .
During rubbing or natural forces , no new charge is created . The charges are either redistributed or a neutron breaks up into proton and electron of equal and opposite charge .
3 . Quantization of charges :
o The charge is always represented in the form of , q = ne . Here n is an integer and e is the charge ( - for electron and + for proton ). Magnitude of e = 1.602192 X 10 -19 This is called quantization of charge .
o SI unit of charge is Coulomb ( C ).
o Quantization is usually ignored at macroscopic levels ( μC ) because at that point , charges are taken to be continuous .
Coulomb ’ s Law
Coulomb ’ s law states that Force exerted between two point charges :