**Coulomb's Law**

Coulomb's law states that the force between two very small objects separated by a distance in space is proportional to the product of their charges and inversely proportional to the square of distance between them.

Let Q1 and Q2 be the charges of two small objects separated by distance R; then by Coulomb's law:

F ∝ Q1 . Q2 ..........1

F ∝ 1/R2 .........2

On combining equation 1 and 2,

F ∝ Q1.Q2 / R2

F = k. Q1.Q2 / R2

where, k is a proportionality constant.

The value of k is given by:

k = 1 / 4πεo

Hence, we can write:

F = (Q1.Q2) / (4πεoR2) where, εo = 8.854 * 10 -12 C2 kg-1 m3 sec2

In vector form:

F2 = (Q1.Q2) / (4πεoR122) . a12

where,

R12 = r2 - r1

a12 = R12 / |R12|

Also,

F1 = - F2

-by **SURAJ AWAL**

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