5C20.10 - Dielectrics

Code Number:
Demo Title:
Effects of a Dielectrics
Area of Study:
Electricity & Magnetism
High Voltage Power Supply, Sliding Plate Capacitor, Electroscope (0 - 3000 V), Dielectric Plates, and Aluminum Plate with Teflon Handle.

Video Credit: Jonathan M. Sullivan-Wood

Hook the sliding plate capacitor to the electroscope, charge the plates with the high voltage power supply to 3000 Volts as read on the electroscope.  Insert the dielectric between the capacitor plates and observe the voltage drop to approximately 1500 Volts.  Removing the dielectric should return the voltage to close to its original value.  The aluminum plate can also be used and thought of in terms of being the perfect dielectric.

NOTE:  At these voltages the dielectric can touch the sliding capacitor plates with negligible effects.

These dielectrics should give these approximate voltage drops:

Halliday and Resnick textbook = 1000 to 1500 volts

Round Phenolic 1" Plate - 1500 volts

Mica = 500 volts

Cardboard = 300 to 500 volts

Thin smooth phenolic sheet = 500 volts

Thick rough phenolic sheet = 1000 volts

  • Youngmin Oh, Taehun Jang, Hyejin Ha, Sangho Sohn, "Temporal Change of a Parallel Plate Capacitor's Voltage After Dielectric Insertion", TPT, Vol. 60, #2, Feb. 2022, p. 124.
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  • Yaakov Kraftmakher, "5.7, Dielectric Constant", Experiments and Demonstrations in Physics, ISBN 981-256-602-3, p. 343.
  • W. Bolton, "31. The Permittivity of Free Space", Book 4 - Electricity, Physics Experiments and Projects, 1968, p. 59 - 61. 

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