Water Dielectric - Physics Demonstrations - Water Dielectric | Physics Undergraduate Labs

Water and electronics do not mix. Clear the area of laptops, projectors, and other sensitive equipment. Keep paper towels within reach. Consider performing this demonstration on a cart that can be easily moved away from technology if needed. Have a contingency plan for cleanup.

Purpose

Water ( $\kappa \approx 80$ ) is poured into a bag between parallel capacitor plates while a meter displays the capacitance in real time. Students watch the reading climb dramatically, providing direct evidence that dielectric materials increase capacitance via $C = \kappa\epsilon_0 A/d$ .

BK Precision 830A capacitance meter displaying 3.42 nF, connected to parallel plate capacitor with circular aluminum plates and empty freezer bag between them, black 2 kg mass behind movable plate, on green surface

Same capacitor setup with water-filled freezer bag between plates, BK Precision capacitance meter now displaying 94.1 nF

Figure 1: Initial setup showing the capacitor with empty plastic bag between plates. The capacitance meter reads a baseline value before water is added.

Figure 2: After filling the bag with water, the capacitance increases dramatically due to water's high dielectric constant (κ ≈ 80), demonstrating the effect of dielectric materials on capacitance.

Pitcher

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Parallel Plate Capacitor

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Safety Warnings

Warning: Water Spill Risk

Purpose