Two point charges are arranged along the –axis

PHYSICS · Multi-part · AP · Physics 2: Algebra-based · Electric Force Field and Potential · Electric Force Field and Potential

Problem

Two point charges are arranged along the

x

–axis. A charge

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

is fixed at the origin. A second charge

q_{2}=+2.5\,\mu\text{C}

is initially at a very large distance (effectively infinity) and is slowly brought to the point

x=0.020\,\text{m}

on the axis. (a) Calculate the electric potential energy

U_{\text{f}}

of the two–charge system when

q_{2}

is at

x=0.020\,\text{m}

. Express your answer in joules. (b) Determine the work

W_{\text{ext}}

done by the external agent in bringing

q_{2}

from infinity to this point. (c) State whether the external agent had to supply energy to the system or remove energy from it, and explain how the sign of

W_{\text{ext}}

supports your conclusion.

Related theory

Electrostatic Potential Energy
Electric Potential
Potential energy of a system of charges
Electrostatic Potential and Capacitance

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