C.5(1) - DRIVING MOTOR

Energy stored in a capacitor is used to drive a small motor that turns a propeller. The circuit consists of eight capacitors in parallel with equivalent capacitance of 30,000 microfarads connected in series with five 500 ohm resistors in series. The time constant for the circuit is 75 seconds. The apparatus is connected to a high voltage power supply set at 250 volts. it is set in a 25 cm x 25 cm board.

C.5(2) - DISCHARGING WITH A METAL BAR

A capacitor (100 microfarad, 2500 V DC) is charged up for a few minutes at 1.5 kVolts. The capacitor is connected in series with a resistor (13 x 10⁴ ohm), and to the power supply through a switch. After it has been charged, turn the power off and open the switch. the capacitor is then shortened with a big metal bar with insulated handle, causing a big spark and loud blast. (The time constant for the circuit is 13 seconds.)

C.5(3) - WIRE EXPLODER

A large capacitor (240 microfarads, 5000V) is used as the supporting stand for an arrangement that surprisingly shows the energy stored in a capacitor. Thick plexiglass sheets are placed over it and around the set-up consisting of: an electromagnetic switch, a small meter, resistors and the stand that firmly holds a very thin metal wire, as shown in the figure. The power supply and a long wire switch are set by its side. The capacitor is charged up during 5-10 minutes at 2000 V DC through a resistor R=1.8 x 10⁶ ohm (or until the meter indicates at least 15-20 minutesA). Turn the power supply off. Take the switch and step away from the apparatus. Close and open the remote switch. When the circuit is closed, the capacitor will discharge through the thin wire pulverizing it. It causes a big blast, a big spark and even some smoke. The time constant for this circuit is 432 seconds. After being charged for 5 minutes, the charged accumulated on the capacitor is about 0.24 Coulomb and the total energy released on the instant of explosion is about 173 Joules. It is very loud and very surprising. Be aware that the capacitor might still be charged since the wire explosion usually does not discharge it completely. A discharger with long handles is used to do it, followed by another smaller blasts and sparks.