SAT Subject Physics Practice Question 239: Answer and Explanation

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Question: 239

10.

An electric dipole, a pair of equal but opposite charges. Two isolated point charges are fixed in the positions shown on the y axis; the positive charge is located at the point (0, b) and the negative charge is located at the point (0, –b).

Which graph best depicts the electric field magnitude along the x axis, from x = –a to x = a?

A.
B.
C.
D.
E.

Correct Answer: B

Explanation:

The electric field strength is strongest at x = 0. It increases from x = –a to x = 0, then decreases from x = 0 to x = a. Therefore, only graphs B and E are possible. However, since the electric field strength at x = 0 is not zero, the answer cannot be E.

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