Cuesta College, San Luis Obispo, CA
Cf. Giambattista/Richardson/Richardson, Physics, 2/e, Problem 20.55.
Consider an ideal emf source connected to an ideal resistor and inductor. The switch is closed at t = 0. After the switch is closed, the current through the inductor __________, while the current through the resistor __________. (A) decreases to zero; decreases to zero.
(B) decreases to zero; increases to a finite value.
(C) increases to a finite value; decreases to zero.
(D) increases to a finite value; increases to a finite value.
Correct answer: (D)
The junction rule states that the amounts of current passing through the resistor and inductor must all be identical. From inspection, the current I in all parts of this circuit starts from an initial value of 0, and increases to its limiting value of I = emf/R after a long time, when the inductor is no longer reacting to the change in current, such that the amounts of current through both the resistor and inductor increases to a finite value.
Student responses
Section 30822
Exam code: quiz06eMf0
(A) : 0 student
(B) : 5 students
(C) : 1 student
(D) : 2 students
Success level: 25%
Discrimination index (Aubrecht & Aubrecht, 1983): 0.67
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