5F30.10 Capacitor and Light Bulb


Charging and discharging of a capacitor


Immediately after the capacitor is connected to the battery, the light bulb will glow as current flows through the light bulb and the capacitor is charging. After some time, the capacitor is fully charged and the light bulb is no longer glowing. When the switch is turned, the capacitor is discharged and the bulb starts to glow again until the capacitor loses all of its stored energy and the current in the circuit is not sufficient to heat up the filament of the bulb.



  • [1] 6 V lantern battery
  • [1] SPDT switch
  • [1] 155,000 μF capacitor
  • [1] Small light bulb
  • [5] Banana cable
  • [2] Alligator clip

Classroom Assembly

  1. Place the components of the circuit on the table.
  2. Build the circuit as shown on the diagram.

Important Notes

  • Ensure the circuit components are properly attached before connecting the battery


  1. Turn the switch to connect the capacitor to a battery and start the charging cycle.
  2. Wait for some time after the light bulb is turned off to make sure that the capacitor is fully charged.
  3. Turn the switch to start the discharging cycle.
  4. Disconnect the battery.


Additional Resources


  • PIRA 5F30.10


  • Don't attempt this at home!

Last revised

  • 2020


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If you have any questions about the demos or notes you would like to add to this page, contact Ricky Chu at ricky_chu AT sfu DOT ca.