Question

The two charges $7\mu C\text{and}-2\mu C$ are separated by a distance of 18 cm. The work required by you to separate the two charges infinitely away from each other is:

• A. 0.7 J
• B. -0.7 J
• C. 1.4 J
• D. -1. 4 J

Answer 1

The correct option is B -0.7 J

$U=\frac{1}{4\pi {\epsilon }_0}\frac{q_1{q}_2}{r}$

$U=9\times {10}^9\times \frac{(7\times {10}^{-6})(-2\times {10}^{-6})}{18\times {10}^{-2}}$

$U=-0.7J$