Equipment: A closed wire loop attached in series to a bulb (a search coil), and a degaussing coil.

What it does: The search coil lights up when placed in certain orientations in and around the degaussing coil. It is brightest when the search coil is in the center of the degaussing coil and is perpendicular to the direction of the changing field. The bulb is dark (no current produced) when the search coil is parallel to the changing field.

Concepts Demonstrated: Induction of a current in a closed loop due to a changing magnetic field.

Classroom assembly:

1. Plug in and turn on the degaussing coil.
2. Hold the search coil in the center of the degaussing coil.
3. Rotate the search coil to demonstrate that the bulb lights up in some orientations, but not in others.
4. Move the search coil around the degaussing coil.

Cautions: The degaussing coil becomes hot over time. Turn off when not in use.

Setup Time: Short.

Difficulty: Straightforward.

Visibility: Medium. The apparatus is small but the lighted bulb is visible from the back of a large lecture hall when the room lights are dimmed.

Related demonstrations:

References:

Original Construction: The coil of wire is a 100' spool of 20 gauge hook up wire. The two ends of the wire were soldered to a bulb to produce a closed loop with the bulb in series. The degaussing coil was purchased.