Force on Parallel Conductors - Physics Demonstrations - Force on Parallel Conductors | Physics Undergraduate Labs

This is a short circuit across 12V; the wires heat up quickly. DO NOT leave the switch closed — close it lightly and open it again immediately. Keep the positive terminal disconnected until you are ready to demonstrate.

Purpose

Shows the magnetic force between parallel current-carrying wires: parallel currents attract, antiparallel currents repel. A fiber optic lamp projects wire shadows onto a white backdrop so the motion is visible in large lecture halls.

Two long black rubber-insulated wires hanging from a wooden clamp on a vertical support rod, with a white paper backdrop behind them, a red Optima 12V battery and switch on the bench below, and heavy orange leads connecting the circuit

Side view showing the fiber optic lamp (blue box), red Optima battery with alligator clips, wooden support rod with bench clamp, white paper backdrop, and orange insulated leads

Close-up overhead view of double-pole switch junction box with six brass terminal posts, orange and green insulated wires connected, black and brown wires, metal plate base

Overhead view of switch junction box showing orange, green, and brown wires connected to brass terminals with yellow identification rings on bottom posts, demonstrating alternate wiring configuration

Figure 1: Full apparatus: two hanging wires suspended from a clamp, white paper backdrop for shadow projection, 12V battery and switch below. The wires are held loosely enough to move when current flows.

Figure 2: Side view showing the fiber optic lamp for shadow projection, 12V battery, and the support structure.

Figure 3: Double-pole switch configured for parallel currents (same direction). Moving the hanging wires to opposite corners gives antiparallel currents.

Figure 4: Switch reconfigured for antiparallel currents (opposite directions).

12 V Battery

1

Safety Warnings

Warning: High Current — Short Circuit

Purpose