SAT Subject Physics Practice Question 302: Answer and Explanation

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Question: 302

73. An electron that accelerates from a point near a collection of negative source charges toward a point near a collection of positive source charges experiences

A. a decrease in electrical potential energy as it moves toward a region at a lower electric potential
B. a decrease in electrical potential energy as it moves toward a region at a higher electric potential
C. an increase in electrical potential energy as it moves toward a region at a lower electric potential
D. an increase in electrical potential energy as it moves toward a region at a higher electric potential
E. no change in electrical potential energy

Correct Answer: B

Explanation:

Since the electron is naturally being accelerated toward a region containing positive source charges, its potential energy decreases. (It’s like a ball dropping to the ground; it is accelerated downward by the gravitational field, and it loses gravitational potential energy.) Therefore, the answer is either A or B. Now since the potential due to a positive charge is higher than the potential due to a negative charge (because positive numbers are greater than negative numbers), the electron is accelerating toward a region of higher electric potential choice B.

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