Three point charges 1C, 2C and 3C are placed at the corners of an equilateral triangle of side 1m.

The work required to move these charges to the corners of a smaller equilateral triangle of side 0.5 m in two differenct ways as in fig. (A) and fig. (B) are W_(a) and W_(b) then:

Work done = Change in potential energy = U(final) - U(initial) , and,

U = k{ (Q1.Q2)/r1 +(Q2.Q3)/r2 +(Q3.Q1)/r3 }, where k = 9x10^9

Initially, when charges are kept in equilateral triangle of side 1 m :

Since triangle is equilateral, r1 = r2 = r3 = r = …