A Dielectric's Effect on Capacitance

Overview

Objectives/Goals The objective is testing the effects of different dielectric materials on capacitance by building capacitors with different materials and physical dimensions. Tests were done by charging the capacitors in a basic resistor-capacitor circuit. Methods/Materials Five home-made capacitors (aluminum foil, a dielectric or insulating layer, and wire); voltage-current multimeter; 100 megohm resistor; 6-V battery; timer. Measured the time required to charge each capacitor and then applied fundamental physics theories to calculate the dielectric constant of each insulating material used in the capacitors. Results Repeated trials (20 per capacitor), in which I measured the current, allowed me to determine the time constant of the resistor-capacitor circuit. Following calculations found the capacitance of each capacitor, the electric permittivity of the dielectric, and finally the dielectric constant of each material. Conclusions/Discussion Because the capacitors were home-made, there was a significant leakage current through the capacitors. Inaccuracies in the current measurement led to some dielectric constants being apparently less than 1 (below the theoretical limit!). Despite this problem, I could measure the dielectric constant of the materials relative to each other.

Competition history

• CSEF 2017 Materials Science (Junior Division Only) · Entry J1417

Resources

• CSEF project summary ↗

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