Hey everyone, I am reviewing for an exam by going over some practice tests thatm

Question

Hey everyone,

I am reviewing for an exam by going over some practice tests thatmy prof handed out. Below are two questions from one of his exams,followed by his solutions. I am a little confused. Don't these twoanswers contradict each other? Any help would be greatlyappreciated. Thanks! -A

Q. A resistor and an inductor are connected in series to anideal battery of constant terminal voltage. At the moment contactis made with the battery, the voltage across the resistoris
A. Zero, because the current builds up exponentiallyfrom an initial value of zero. If there is no current through aresistor, Ohm's law tells us that the voltage across it is zero v =IR

Q. A resistor and a capacitor are connected in series to anideal battery of constant terminal voltage. At the moment contactis made with the battery, the voltage across the resistoris:
A. It is equal to the batter's terminal voltage. This is because atthe moment contact is made with the batter, no charge has yetaccumulated on the capacitor and the voltage across the capacitorwill then be zero (from Q=CV). Therefore, the entire voltage dropis across R (Kirchhoff's loop).

Explanation / Answer

It might seem that they do contradict each other, butthey actually do not. . Both answers are correct. There is an important differencebetween the two questions: in the first question, a resistor isconnected to an INDUCTOR in the circuit; in the secondquestion, the resistor is connected to a CAPACITOR. . The two answers are different because of the differentbehavior of a capacitor and inductor in a circuit. The two answersdescribe these behaviors... and it's important to realize that theanswers are different because one is describing the circuit withthe inductor, while one describes the circuit with thecapacitor.

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