Question

For two like charges (both positive or both negative), the sign of \[(q_1 q_2)\] and the resulting sign of the potential energy U are:

Options

• Positive; U > 0

• Positive; U < 0

• Negative; U < 0

• Zero; U = 0

Answer 1

For like charges, the product \[q_1 q_2\] is positive (both charges positive or both negative), so \[U = \frac{1}{4\pi\varepsilon_0}\cdot\frac{q_1 q_2}{r_{12}} > 0\]. Energy must be supplied to overcome their mutual repulsion.