5C30.20-Short a Capacitor


Video: Watch this demo

Instructor’s video

Description: This demo shows what happens when you short a large capacitor.


  • High voltage DC power supply
  • Industrial strength 100microfarad 800VDC capacitor
  • Large screwdriver
  • Two wires

Setup Procedure:

  1. Disconnect the shorted wire from the capacitor.
  2. Connect the power supply cables to the capacitor.
  3. Adjust the power supply to about 400VDC.
  4. When the professor is done, discharge the capacitor again and connect a wire to short the terminals.

Demonstration Procedure:

  1. Turn on the power supply and let it charge for about 30 seconds.
  2. Turn the power supply to standby.
  3. While holding the insulated handle, touch the screwdriver to both terminals of the capacitor and watch the large spark.
  4. When finished, turn the power supply off and discharge the capacitor for safety.

Concept: This demo is simply used to illustrate how you can quickly discharge a capacitor. To “short” a capacitor means to place a conductor directly from one terminal to another to allow the capacitor to quickly discharge rather than to do so slowly, causing a spark.

High Voltage / High Current
This capacitor can hold a lethal charge!
Never touch the terminals.
Always discharge the capacitor after use. Attach a cable connecting both terminals when putting away for safety.