Question

Calculate the amount of work done to dissociate a system of three charge 1 μC, 1 μC and - 4 μC placed on the vertices of an equilateral triangle of side 10 cm.

Answer 1

Work done = \(\Delta U\)

\(U_f = 0\)

\(U_i = \frac{k \,10^{-6} \times 10^{-6}}{(0.1)} + \frac{k\, 10^{-6} \times (-4) \times 10^{-6}}{(0.1)} + \frac{k\, 10^{-6}(-4)\times 10^{-6}}{(0.1)}\)

\(= \left( \frac k{0.1} - \frac{8k}{0.1}\right) \times 10^{-12}\)

\(= \frac {-7k}{0.1} \times 10^{-12}\)

\(= -7 \times 9 \times 10^9 \times 10^{-11}\)

\(= -63 \times 10^{-2}\)

\(= -0.63 \) J

W = U_f - U_i

= 0 - (-0.63 J)

= 0.63 J

Answer 2

Given:

W = -.63 J