Big Bang Capacitor

This demonstration consists of a 3kV, 580 μF capacitor mounted on a dolly with a 1kV power supply mounted above it.

Discharge a capacitor charged up to 1kV with an impressive 'bang!'. This effectively illustrates how energy can be stored with capacitors, this can also be used to talk about RC circuits (an example of an RC circuit with a very short time constant).

Also provides an exceedingly effective method to wake up drowsy undergrads.

• 'Big bang' Capacitor demo
• Discharge wand (long wooden stick with copper bar on the end)
• Wire short
• Checklist

The notes below are just an expanded transcription of the text of the checklist included with the demo. When running this demonstration, keep the checklist handy and refer to it if there's any doubt.

1. Unclip the wire short from the terminals. If for whatever reason they were not already in place, short the capacitor with the discharge wand.
2. Connect the power supply to the terminals.
3. Plug the power supply in, and turn the power on.
4. Charge the capacitor to 1kV. Note that there will be a delay of about 30 seconds before the needle on the voltage meter will begin to move.
5. Next, remove the leads from the capacitor by pulling the attached strings. Take utmost care in this step; pull them off the terminals in a way that guarantees they have no chance of touching you. Place them on the ground away from each other.
6. Turn off the power supply.
7. Here's the fun part: Put on your eye and ear protection and use the discharge wand to discharge the capacitor.¹⁾ Feel free to perform a bit, do a dramatic count-down before you discharge the capacitor.
8. Make absolutely certain that the capacitor is discharged, then immediately replace the wire short across the terminals. Make sure the connection is good!

Any time you're about to touch the leads be sure to short the terminals together multiple times immediately before doing so. If you charge it up to 1kV, discharge it, and come back a couple minutes later to place the short wire on the terminals, you may recieve a nasty shock! Dielectric Absorption is responsible for this. If the capacitor is left un-shorted for any amount of time, it's healthy to assume it has some charge stored.