Magnetic Field Around Single And Parallel Wires
To visualize the magnetic field around a wire and near two wires carrying opposite currents. ◙
Magnetic field of single wire/wire loop combination with 7.5 volt battery and iron filings on overhead◙projector.
A large number of turns of small wire are used to produce a larger current, which passes through a plastic sheet on an overhead projector. Two current sources are available on this one: a single wire and two nearby wires with equal but opposite currents. Sprinkling iron filings on the plastic sheet near the wires and gently tapping the sheet causes the filings to line up along the magnetic field lines. ◙A heavy-duty 7.5 volt battery is used as the power source.
Dwight E. Neuenschwander and Brian Turner, Generalization of the Biot-Savart law to Maxwell's equations using special relativity, AJP 60, 35-38 (1992).