Demonstrations

Dielectrics

Code Number :	5C20.10
Disclaimer:	Reprinted by permission of Dick Berg, University of Maryland, for use on this website. The demonstrations contained and referenced herein are listed for the purposes of cataloging and describing physics demonstrations which should be conducted only under the direction of a trained instructional support professional or physicist. These demonstrations are not presented for the purpose of being conducted by persons unconnected to this Facility and/or persons not consulting with or being supervised by the recognized instructional support professional or physicist and his/her staff. The University is responsible only for those demonstrations carried out using its own equipment using established safety and scheduling policies, and bears no responsibility for those choosing to use this source material for their own purposes. All demonstrations described and contained herein are public domain, and can also be found in reference materials in libraries, bookstores, and electronic sources. Further information regarding legal liability in use of demonstrations and labs will be found on the web site Injuries in School/College Laboratories in USA. The University of Iowa Disclaimers: University of Iowa Disclaimer All Rights Reserved..
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, Aluminum plate with Teflon handle.
Procedure :	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

Web Links

Question of the Week (QOTW) #110. Department of Physics University of Maryland. http://www.physics.umd.edu/lecdem/outreach/QOTW/arch6/q110.htm

References

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. Karlow, "Let's Measure the Dielectric Constant of a Piece of Paper", TPT, Vol. 29, # 1, Jan. 1991, p. 23.

Walter Connolly, "Measuring Capacitance and the Dielectric Constant", TPT, Vol. 26, # 3, Mar. 1988, p. 169.

Oleg D. Jefimenko, David Walker, "Electrets", TPT, Vol. 18, # 9, Dec. 1980, p. 651.

S. K. Chakarvarti, "Permittivity of Free Space and Dielectric Constant Measurement", TPT, Vol. 19, # 2, Feb. 1981, p. 120.

John W. Hammann, "Characteristics and Nature of Dielectrics", TPT , Vol. 3, # 8, Nov. 1965, p. 354.

"Change of Energy of a Charged Capacitor", TPT, Vol. 2, # 3, March 1964, p. 137.

T. T. Grove, M. F. Masters, 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. Ultreras-Diaz, "Dielectric Slab in a Parallel-Plate Condenser", AJP, Vol. 56, # 8, Aug. 1988, p. 700.

A. Gingle, 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, p. 375, ~1954.

Mail Questions and Comments to: Dale Stille