Physics quiz question: change in electric potential energy

Physics 205B Quiz 4, spring semester 2014
Cuesta College, San Luis Obispo, CA

Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 17.3

Two point charges lie along the x-axis. A +6.0 nC charge is at the origin, and a –6.0 nC charge is at x = +5.0 cm. __________ the distance between these two charges would increase their electric potential energy.
(A) Decreasing.
(B) Increasing.
(C) (Both of the above choices.)
(D) (Neither of these choices.)

Correct answer (highlight to unhide): (B)

These two charges will attract each other, which allowed to move due only to this force would tend to decrease their electric potential energy. Separating these two charges would require work to be put in by an external agent, which would cause the electric potential energy to increase.

Sections 30882, 30883
Exam code: quiz04mCnC
(A) : 11 students
(B) : 25 students
(C) : 0 students
(D) : 0 students

Success level: 69%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.89

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