Shorting a Capacitor
Safety Warnings
Warning: Voltage Setting
Danger: High Current Discharge
Warning: Eye Protection
Warning: Capacitor Retains Charge
Purpose
A 90,000 μF capacitor charged to 25V is shorted with a screwdriver, producing dramatic sparks and temporarily welding the screwdriver to the terminals. Demonstrates that even modest stored energy (\(U = \frac{1}{2}CV^2 \approx 28\) J) becomes dramatic when released in milliseconds.
Figure 1:
Setup: 90,000 μF capacitor connected to DC power supply. The 0.0A reading indicates charging is complete. Screwdriver ready for discharge.
Figure 2:
The discharge: ~28 joules released in milliseconds produces intense sparks as thousands of amperes flow through the screwdriver.
Figure 3:
After discharge: the screwdriver is temporarily welded to the terminals — firmly enough to lift the capacitor.