Practice portal › Electric Potential and Capacitance › Electrostatic Potential Energy

Three charges, each +q, are placed at the corners of an isosceles triangle ABC of sides BC and AC, 2a. D and E are the mid points of BC and CA. The work done in taking a charge Q from D to E is

Asked in CBSE AIPMT 2011 Mains · Work done in moving a charge

Figure: Work done in moving a charge
Answer: (4) zero

Step-by-step solution

W=Q(V_E-V_D).

Because BC=AC, the triangle is symmetric about the line through C perpendicular to AB; the reflection swaps A and B and swaps D (midpoint of BC) with E (midpoint of CA).

D: B and C at distance a, and A at distance AD.

E: C and A at distance a, and B at distance BE; by the symmetry BE=AD.

So V_D=V_E and W=0.

Why the other options are wrong

More Electrostatic Potential Energy questionsAll Electrostatic Potential Energy questions →

Reading this solution needs no sign-in. You only sign in to practise against the clock and keep your progress.

Practise this with a timer