AP Physics C: Electricity & Magnetism 9.1 A Describe the Electric Potential Energy of a System Questions

Practise describing electric potential energy by summing pairwise charge interactions, comparing configurations, and relating assembly work to energy changes.

Exam points

Sum kq_iq_j/r_ij over each distinct charge pair to calculate the total potential energy of the system.
Use charge signs and separations to rank the potential energy of different configurations.
Relate external assembly work or electric-field work to the corresponding change in potential energy.

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Questions 31-33

Figure for Question AP Physics C: Electricity & Magnetism 9.1 A Describe the Electric Potential Energy of a System Questions 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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AP Physics C: Electricity & Magnetism 9.1 A Describe the Electric Potential Energy of a System Questions question 1