Question

For the symmetrical arrangement of charges +q, -q, +q, -q at the corners of a square, the electric potential at the centre E due to the four charges is:

Options

• Zero, because the potential from the +q pairs is exactly cancelled by the potential from the -q pairs, since all charges are equidistant from E

• Negative, because there are two negative charges

• Positive, because there are two positive charges

• Infinite, because E is equidistant from all four charges

Answer 1

Since all four corners are equidistant from the centre E, the potentials from the $+q$ charges exactly cancel those from the $-q$ charges, giving $V_E = 0$ at the centre of the symmetrical arrangement.