Three point charges are fixed at the corners of an equilateral triangle of side kept…

PHYSICS · Subjective · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance

Problem

Three point charges are fixed at the corners of an equilateral triangle of side

a

kept in vacuum. Two of the charges are identical and equal to

+q

each. The third charge, placed at the remaining vertex, is an unknown charge

Q

. (a) Derive an expression for the total electrical potential energy

U(Q)

of the system in terms of

q

Q

and

a

. (b) Determine the value (magnitude and sign) of

Q

for which

U(Q)

becomes zero. (c) If the charge found in part (b) is used, calculate the work that must be done to remove one of the

+q

charges to infinity while the other two charges remain fixed.