2D Faraday Cage - Physics Demonstrations - 2D Faraday Cage | Physics Undergraduate Labs

Plasma disks operate at high voltages (typically 10-50 kV) at high frequency. While the current is very low and generally safe to touch, individuals with pacemakers or other electronic medical devices should not participate. Avoid touching the metal ring and plasma disk simultaneously with both hands (creating a path across the chest).

Purpose

A metal ring on a plasma disk creates a 2D Faraday cage: discharge paths route around the ring's perimeter but never cross its interior. Students see direct visual evidence that the electric field inside a closed conductor is zero, illustrating Gauss's Law and electrostatic shielding.

Plasma disk with metal ring in place; a hand touches the back and discharge paths form a bright circle at the ring edge, with streamers branching around but not crossing the interior

Plasma disk without the metal ring, showing discharge paths spreading freely across the entire disk surface; the copper ring sits on the table beside the disk

Figure 1: With the metal ring on the plasma disk, discharge paths illuminate the ring's perimeter and route around it. The interior remains dark — no field lines penetrate the conducting loop.

Figure 2: Without the ring, discharge paths spread freely across the entire disk surface. The copper ring sits on the table for comparison. Contrast this with the shielded pattern when the ring is in place.

Plasma Disk

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Safety Warnings

Warning: High-Frequency High Voltage

Purpose