Equipment: Two square U-shaped wires, a Plexiglas frame and a Xantrex HPD 15-20 power supply.

What it does: The current carrying wires attract and snap together or repel each other depending on the relative direction of current in the wires.

Concepts Demonstrated: The attraction or repulsion between two current carrying wires.

Classroom assembly:

1. Place the wires in the holes that are closest together.
2. Connect the patch cables so that current flows in opposite directions in each wire.
3. Place the Plexiglas platform on the overhead projector.
4. Turn on the power supply and turn up the voltage and current until the wires repel.

1. Place the wires in the holes that are farthest apart.
2. Connect the patch cables so that the current flows in the same direction in each wire.
3. Place the Plexiglas platform on the overhead projector.
4. Turn on the power supply and turn up the voltage and current until the wires snap together.

Cautions: The copper wires become hot over time. Turn off when not in use.

Setup Time: Short.

Difficulty: Straightforward.

Visibility: High. This demonstration can be shown on the overhead projector and is appropriate for large lecture halls.

Related demonstrations:

References:

Original Construction: Two 16.5" lengths of 20 gauge wire were bent into a ‘swing’ shape (a square U with arms on each end). Four Plexiglas legs were attached to a 5" x 8.5" Plexiglas plate to form a raised platform. Four banana plug contacts were threaded through the Plexiglas platform and were each attached to a .5" x 1" copper plates. One or two holes were drilled in the plates so the copper ‘swings’ could be either .5 cm or 2.5 cm apart.