Question

A system of two charges separated by a certain distance apart stores electrical potential energy. If the distance between them is increased, the potential energy of the system,

• A. may increase or decrease
• B. increases in any case
• C. remains the same
• D. decreases in any case

Answer 1

Answer: (A)

Potential energy of a system of charges is $U=\left(\frac{1}{4\pi {\epsilon }_0}\right)\frac{q_1{q}_2}{r}$
In case of like charges, $\left(q_1{q}_2\right)$ is positive
when r increases, U decreases
In case of unlike charges, $\left(q_1{q}_2\right)$ is negative
when r increases, $\left|U\right|$ decreases
but because of negative sign, U increases.