A point charge is fixed at the origin

PHYSICS · Multi-part · CBSE · Physics · Electrostatic Potential and Capacitance · Electrostatic Potential and Capacitance

Problem

A point charge

q_{1}=+3.0\,\mu\text{C}

is fixed at the origin. A second point charge

q_{2}=-2.0\,\mu\text{C}

is fixed on the positive

y

–axis at

y=0.40\,\text{m}

. A third point charge

q_{3}=+1.0\,\mu\text{C}

is initially very far away and is later placed at the point

(0.30\,\text{m},\,0)

on the positive

x

–axis. (a) Calculate the total electric potential energy of the system before

q_{3}

is added. (b) Calculate the total electric potential energy after

q_{3}

is in place. (c) Determine the change in the system’s electric potential energy due to bringing in

q_{3}

. State whether external work must be done on the system or by the system and explain the sign of your answer.