RC Circuit with a Switch

A battery, switch, capacitor, and lightbulb are connected in series. The switch is initially open.

Part 1

Describe what happens to the lightbulb when the switch is closed.

Answer Section

• Nothing. Current cannot flow across the capacitor, so the lightbulb remains dark.

• When the switch is first closed, the current through the lightbulb is high and the lightbulb shines brightly. As the capacitor charges, the current decreases to zero, and the brightness of the lightbulb decreases until it becomes completely dark.

• When the switch is first closed, the current through the lightbulb is low and the lightbulb shines dimly. As the capacitor charges, the current increases and the brightness of the lightbulb increases until it becomes very bright.

• Current flows and the lightbulb turns on.

• As the capacitor charges and discharges, the current flowing in the circuit fluctuates, causing the lightbulb to fluctuate between being bright and dark.

Attribution

Problem is from the OpenStax University Physics Volume 2 textbook, licensed under the CC-BY 4.0 license.