Problem

Two identical thin rings, each of radius

R

, are coaxially placed a distance

R

apart. If

Q_1

and

Q_2

are respectively the charges uniformly spread on the two rings, the work done in moving a charge

q

from the centre of one ring to that of the other is (JEE 1992) (a) zero (b)

\frac{q(Q_1 - Q_2)(\sqrt{2} - 1)}{\sqrt{2}(4\pi\epsilon_0 R)}

(c)

\frac{q\sqrt{2}(Q_1 + Q_2)}{(4\pi\epsilon_0 R)}

(d)

q(Q_1 / Q_2)(\sqrt{2} + 1)\sqrt{2}(4\pi\epsilon_0 R)