Question

Derive an expression for potential energy of a system of two charges in the absence of external electric field.

Answer 1

Consider 2 point charges q₁ & q₂ are separated by a distance ‘r’ are as shown in the fig.

∴ The change q₁ is bringing from ∞ to given point A, no work done.

i.e. w₁ = 0 parallelly the charge q₂ is bringing from ∞ to given point ‘B’ against us field q₂

∴ work is done it is given by

i.e. w₂ = vq₂

This work done is nothing but potential energy.

& it is given by