Force Between Charged Capacitor Plates

This demonstration requires kilovolt-level voltages. Ensure all high voltage connections are properly insulated and that students maintain safe distances. The power supply should have current limiting capability. Discharge the capacitor plates completely before any adjustments to the apparatus.

Always discharge the capacitor plates using an insulated shorting stick before making any adjustments or approaching the apparatus. Capacitors can retain charge even after power supply is turned off.

Purpose

Quantitatively measures the electrostatic attractive force between parallel capacitor plates using a beam balance. Demonstrates that the force is proportional to $$V^2$$ and connects abstract field concepts to measurable mechanical quantities.

Two black-and-white photos: top shows close-up of beam balance with parallel plate capacitor and guard ring assembly; bottom shows full apparatus on a table with high-voltage power supply connected to the balance

Figure 1: Top: close-up of the beam balance with parallel plate capacitor and guard ring. Bottom: complete setup with power supply on rolling table.

Danger: High Voltage Hazard

Warning: Discharge Procedure

Purpose

Safety Warnings

Danger: High Voltage Hazard

Warning: Discharge Procedure

Purpose