# 5C20.10 - Dielectrics

Code Number:
5C20.10
Demo Title:
Dielectrics
Condition:
Good
Principle:
Effects of a Dielectrics
Area of Study:
Electricity & Magnetism
Equipment:
High Voltage Power Supply, Sliding Plate Capacitor, Electroscope (0 - 3000 V), Dielectric Plates, and Aluminum Plate with Teflon Handle.
Procedure:

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

References:
• 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.
• T. T. Grove and M. F. Masters, "Simply and Accurately Measuring Dielectric Constants Using a Parallel Plate Capacitor: Sometimes You Just Can't Win", TPT, Vol. 47, #5, May 2009, p. 312.
• Paul Gluck, "Force on the Dielectric in a Parallel Plate Capacitor", TPT, Vol. 41, #9, Dec. 2003, p. 521.
• Steven D. Doty and Sandra L. Doty, "Dielectric Breakdown of Air as Order-of-Magnitude Physics", TPT, Vol. 36, #1, Jan. 1998, p. 6.
• Edwin A. Karlov, "Let’s Measure the Dielectric Constant of a Piece of Paper!", TPT, Vol. 29, #1, Jan. 1991, p. 23.
• Ellis D. Noll, "Measuring Capacitance and the Dielectric Constant", TPT, Vol. 26, #3, Mar. 1988, p. 169.
• S. K. Chakarvarti, "Permittivity of Free Space and Dielectric Constant Measurement", TPT, Vol. 19, #2, Feb. 1981, p. 120.
• Oleg D. Jefimenko and David K. Walker, "Electrets", TPT, Vol. 18, #9, Dec. 1980, p. 651.
• John W. Hammann, "Characteristics and Nature of Dielectrics", TPT, Vol. 3, #8, Nov. 1965, p. 354.
• "Little Stinkers: Change of Energy of a Charged Capacitor", TPT, Vol. 2, #3, Mar. 1964, p. 137.
• Bart H. McGuyer, "Frequency-Dependent Capacitors Using Paper", AJP, Vol. 89, #4, April 2021, p. 370.
• T. T. Grove, M. F. Masters, and R. E. Miers, "Determining Dielectric Constants Using a Parallel Plate Capacitor", AJP, Vol. 73, #1, Jan. 2005, p. 52.
• Eric R. Dietz, "Force on a Dielectric Slab: Fringing Field Approach", AJP, Vol. 72, #12, Dec. 2004, p. 1499.
• Constantino A. Utreras‐Díaz, "Dielectric Slab in a Parallel-Plate Condenser", AJP, Vol. 56, #8, Aug. 1988, p. 700.
• A. Gingle and T. M. Knasel, "Undergraduate Laboratory Investigation of the Dielectric Constant of Ice", AJP, Vol. 43, #2, Feb. 1975, p. 161.
• Francis T. Worrell, "An Experiment on the Dielectric Constant of a Gas", AJP, Vol. 22, #6, Sept. 1954, p. 375.
• 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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