Q. 13.8( 5 Votes )
In the figure, the dotted circle is an equipotential surface due to the inner charge + Q.
The voltage at all points of an equipotential surface is the same (i.e. VA = VB = VC)
We know that work done by a point charge in moving from one point to another W = q × ΔV
Work done by moving a charge from A to B is W1 = q × (VA-VB) = 0
Work done by moving a charge from B to C is W2 = q × (VB-VC) = 0
Total work is done in moving a charge from A to B and then B to C is W1 + W2 = 0.
Thus we can conclude that work done by moving a charge from one point to another on an equipotential surface is always zero.
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