The diagrams show three circuits with identical batteries, identical inductors, and identical resistors. Rank them according to the current through the battery just after the switch is closed, from least to greatest.
A) 3, 2, 1
B) 2 and 3 tie, then 1
C) 1, 3, 2
D) 1, 2, 3
E) 2, 3, 1

Question

The diagrams show three circuits with identical batteries, identical inductors, and identical resistors. Rank them according to the current through the battery just after the switch is closed, from least to greatest. 
A) 3, 2, 1 
B) 2 and 3 tie, then 1 
C) 1, 3, 2 
D) 1, 2, 3 
E) 2, 3, 1

Quizplus · Accepted Answer

The current through an inductor cannot change instantaneously, so just after the switch is closed, the inductor in Circuit 1 will prevent any current from flowing through the circuit, resulting in no current through the battery. In Circuit 3, the inductor is short-circuited by the wire, allowing the battery to immediately drive current through the resistor, resulting in the greatest current through the battery just after the switch is closed. Circuit 2 falls in between the two, with some initial current flowing through the resistor but less than Circuit 3 due to the presence of the inductor. Therefore, the circuits should be ranked as 1, 3, 2, or choice C.

The Diagrams Show Three Circuits with Identical Batteries, Identical Inductors