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• October 11, 2021

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• PHY102 Physics II © Dr.Cem Özdoğan

• 24-11 Electric Potential Energy of a System of Charged Particles

• The electric potential energy of a system of fixed point charges is equal to the work that must be done by an external agent to assemble the system, bringing each charge in from an infinite distance.

• Figure 24-15 shows two point charges q1 and q2, separated by a distance r.

• When we bring q1 in from infinity and put it in place, we do no work because no electrostatic force acts on q1.

• However, when we next bring q2 in from infinity and put it in place, we must do work because q1 exerts an electrostatic force on q2 during the move.

• The work done is q2V, where V is the potential that has been set up by q1 at the point where we put q2.