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: