Concept about circuits from TBR

[deleted647690]

Hi,
I ran into a question that confused me in the circuits chapter of TBR. Does a capacitor in a circuit cause the current running through the circuit to vary over time?

There was a question that showed a circuit with 3 resistors and a capacitor. R1 was in series with the battery, and R3 and the capacitor were in parallel with the battery.

The closing of switch 1 allowed for completion of the circuit.

The question asked what the current through resistor 1 would be immediately after switch 1 was closed and the capacitor was negligibly charged.

My answer was that it would be the voltage over the equivalent resistance, due to R1 and R3 being in series.

However, the answer explanation was that the current only depended on resistance provided by R1. This was because there was no voltage drop across the capacitor, and thus no voltage drop across R3 since they were in parallel.

This is a strange concept to me, and something I've never encountered in my undergrad physics courses. I wasn't aware that the total resistance could change over time based on the charge of the capacitor, and thus, the current could change over time.

I've attached an image of the circuit.

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[deleted936470]

One or multiple capacitors in a circuit indeed results in a varying current over time. Circuits with resistors and batteries have time-independent functions i.e. the current doesn't change as time goes by. Adding one or more capacitors changes it so that current is a function of time. Closing switch 1 would elicit this phenomenon.

 

[deleted647690]

One or multiple capacitors in a circuit indeed results in a varying current over time. Circuits with resistors and batteries have time-independent functions i.e. the current doesn't change as time goes by. Adding one or more capacitors changes it so that current is a function of time. Closing switch 1 would elicit this phenomenon.

Thank you