Ampere's law: Currents in parallel wires attract or repel.

Ampere's law: Currents in parallel wires attract or repel. When the reversing switch is thrown one way, the current in both wires is flowing the same direction, causing attractive magnetic fields that make the wires jump together. When the switch is thrown the other way, current in one wire flows in a direction opposite to that in the other wire, causing repulsive magnetic fields that make the wires jump apart. 12 V.D.C. (from a car storage battery) is connected through a .09 ohms series ballast resistor to limit the current to 120 amps. A Timer box, set for 20 seconds, is attached across the resistor. It beeps to warn the demonstration operator to turn off the power to the apparatus, to avoid melting of the wires.