Torque on coil suspended between two magnets.

Torque on coil suspended between two magnets. This is a simple galvanometer. Throwing the 'reversing switch' one way sends about 10 amps through a coil of wire mounted on a swivel base. The magnetic field generated by the coil is perpendicular to the plane of the coil. The north end of the coil field is attracted to the south end of the bar magnet field, and so the coil swings through an angle and stays there until the current is turned off. Throwing the switch in the opposite direction causes the coil to swing in the opposite direction. The Timer box reminds the demonstration operator to turn off the apparatus in 5 seconds to avoid melting the wires.