70. Parallel Wires

Large currents passed through two neighboring parallel wires cause them to attract dramatically, or to repel if the currents are passed antiparallel.

A box with parallel and antiparallel wires made of aluminum foil exists for lecture demonstrations. The box sits on the overhead projector and is powered with a 12V supply. The motion of the wires is easily detected by the class as the experiment is magnified on a screen.

A long straight wire demonstration, a solenoid field, and a field of a current loop are available in compass table form. Many tiny compass needles turn to outline the magnetic fields for overhead projection, saving you the trouble of carefully spreading the iron filings.