The magnitude of the force (F) of attraction or repulsion between two point charges q1 and q2 placed in vacuum at separation r is
(a) directly proportional to the product of the magnitude of the two charges.
F a q1q2 ...(i)
(b) inversely proportional to the square of the distance of separation between them.
F a 1/r2 …….. (ii)
COULOMB’S LAW IN VECTOR FORM
Consider two point charges q1 and q2 separated by a distance r. If q1 q2 > 0 i.e. if both q1 and q2 are +ve
or both q1 and q2 are negative then the charges repel each other otherwire they attract each other. If ®F12 is the force exerted on charge q1 by charge q2.
If ®F21 is the force exerted on q2 due to q1 then
Both ^r21 and ^r12 have same magnitude i.e. unity and are oppositely directed
So the forces exerted by charges on each other are equal in magnitude opposite in direction
