Question

Two charges +7 C and –4 C are located at (–7, 0, 0) and (7, 0, 0), find electrostatic potential energy of the system. \(\left(k = \frac{1}{4\pi\ \in_0} = 9 \times 10^9\ \text{SI units}\right)\)

(1) \(-6\times 10^9\ J\)

(2) \(-18\times 10^9\ J\)

(3) \(18\times 10^9\ J\)

(4) \(6\times 10^9\ J\)

Answer 1

Correct option is : (2) \(-18\times 10^9\ J\)

\(E = \frac{Kq_1q_2}{r}\)

\( = \frac{-9\times 10^9\times 7\times 4}{14}\)

\( = -18\times 10^9\ J\)