) = 27 × 107 J Let charge at A is moved to mid-point O, Then final potential energy of the system Uf =
1
4π∊0
[
2q2
(a∕2)
+
q2
a
] = 5 ×
1
4π∊0
(
q2
a2
) = 45 × 107 J Work done = Uf−Ui = 18 × 107 J Also, energy supplied per sec = 1000 J (given) Time required to move one of the mid-point of the line joining the other two t =