Algodoo

A capacitor is an electrical component that stores an electric charge similar to how a battery stores an electric charge. The difference is a battery discharges its stored charge over a long time period, but a capacitor can discharge its stored charge very quickly. That sudden discharge of electricity, depending on the size of the capacitor and the magnitude of the voltage stored in it, can create a very loud "BANG" and a very bright flash.

Technicians who work on electrical circuits that include capacitors understand that it's safer for them to discharge a capacitor with a heavy gauge wire or a metal tool such as a screwdriver before touching it with their hands. For a very high voltage capacitor, as depicted in this scene, the tool doesn't need to make contact with the terminals because the high voltage will jump a distance. That's what makes high voltage circuits especially dangerous.

Move the screwdriver across the electrical terminals to discharge the capacitor. You will see that the spark will occur without even touching the metal tips of both terminals.

Update: Improved contact area.