SAT Subject Physics Practice Question 79: Answer and Explanation

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Question: 79


Which points in the uniform electric field (between the plates of the capacitor) shown above lie on the same equipotential?

A. 1 and 2 only
B. 1 and 3 only
C. 2 and 4 only
D. 3 and 4 only
E. 1, 2, 3, and 4 all lie on the same equipotential, since the electric field is uniform.

Correct Answer: C


6 C Because E is uniform, the potential varies linearly with distance from either plate (∆V = Ed). Since points 2 and 4 are at the same distance from the plates, they lie on the same equipotential. (The equipotentials in this case are planes parallel to the capacitor plates.)

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