Electromagnetic Slides

The demonstration requires sufficient current to generate visible magnetic fields. Always use the rheostat to control current, starting at low settings (30-40) and minimizing the duration of high current flow to prevent overheating the conductor slides. Turn current off immediately after field pattern is established.

Conductor slides will heat up during operation due to Joule heating (P = I²R). Allow slides to cool between demonstrations and avoid touching conductor surfaces immediately after use. The plastic substrate may also become warm.

Purpose

Iron filings on transparent slides reveal magnetic field patterns around various current-carrying conductor geometries (straight wire, loop, coil, parallel wires), projected for the class via overhead projector. Students see direct visual evidence for the Biot-Savart law and right-hand rule.

Top: Blue variable transformer (rheostat), Elenco PE-20 DC power supply (battery eliminator), red connecting leads, and jar of iron filings on a lecture bench. Bottom: Five electromagnetic slides in black frames with different conductor configurations — straight wire, loop, coil, and solenoid cross-sections — with red banana plug connectors.

Figure 1:

Iron Filings

1

Warning: Electrical Current Warning

Warning: Heat Development

Purpose

Safety Warnings

Warning: Electrical Current Warning

Warning: Heat Development

Purpose