Question

A charge −6 pC is placed at the centre B of a semicircle of radius 5 cm, as shown in the figure. An equal and opposite charge is placed at point D at a distance of 10 cm from B. A charge +5 μC is moved from point ‘C’ to point ‘A’ along the circumference. Calculate the work done on the charge.

Answer 1

Electric potential at any point due to a charge q at a distance r:

V = kq/r

Since C and A are at the same distance from B (radius = 5 cm), the potential at both points due to B and D is the same.

Thus, the potential difference between C and A is zero, meaning:

W = q ΔV = 0