AP Physics C E&M 9.1: Electric Potential Energy

Practise AP Physics C E&M 9.1 by calculating electric potential energy for point-charge systems, comparing configurations, and connecting work to energy changes.

Exam points

Calculate total electric potential energy by summing kq_iq_j/r_ij for every charge pair.
Compare charge configurations using the signs and separations in each pairwise energy term.
Relate electric-field or external work to changes in potential and kinetic energy.

Covered syllabus points

9.1.A—Describe the electric potential energy of a system

[Maximum number: 1]

Questions 31-33

Figure for Question 9.1 Electric Potential Energy question 1 — AP Physics C: Electricity & Magnetism

Two small spheres have charges +Q and -Q and are located at the bottom corners of an equilateral triangle, as shown in the figure above. The equilateral triangle has sides of length a, and point P is at the top corner of the triangle.

The potential energy stored in the charge configuration shown is

$\frac{Q^{2}}{4 \pi \varepsilon_{0} a}$

$\frac{Q}{4 \pi \varepsilon_{0} a^{2}}$

zero

$-\frac{Q}{4 \pi \varepsilon_{0} a^{2}}$

$-\frac{Q^{2}}{4 \pi \varepsilon_{0} a}$

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Covered syllabus points

9.1 Electric Potential Energy question 1