5C20.22 - Forces on a Dielectric

Pour Silicon Oil into the Petri dish to a depth of 1/4 inch.  Place the electrodes into the dish and space them about 1/8 in apart.  The higher you turn up the voltage on the power supply, the higher the oil will climb in the gap between the electrodes.  The oil should rise at least 1 to 1.5 cm up into the gap.
Caution:  If you turn the voltage up too fast you will get arcing of the electrodes.  Turn the voltage down and then up slowly.  As the oil rises into the gap you will be able to apply more voltage. If the electrodes are too close together, you will also get continuous arcing between them and the demo will fail.
Mineral oil may be substituted for the Silicon oil but it will not rise up into the gap as far.
Code Number:
5C20.22
Demo Title:
Forces on a Dielectric
Condition:
Excellent
Principle:
Forces on Dielectrics
Area of Study:
Electricity & Magnetism
Equipment:
High Voltage Power Supply, Aluminum cylinder electrodes, Silicon Oil, Mineral Oil, 6 inch Petri Dish.
Procedure:

Pour Silicon Oil into the Petri dish to a depth of 1/4 inch.  Place the electrodes into the dish and space them about 1/8 in apart.  The higher you turn up the voltage on the power supply, the higher the oil will climb in the gap between the electrodes.  The oil should rise at least 1 to 1.5 cm up into the gap.  

Caution:  If you turn the voltage up too fast you will get arcing of the electrodes.  Turn the voltage down and then up slowly.  As the oil rises into the gap you will be able to apply more voltage. If the electrodes are too close together, you will also get continuous arcing between them and the demo will fail.

Mineral oil may be substituted for the Silicon oil but it will not rise up into the gap as far.

References:
  • Chen Xuan, "Enlightening Visualizations of Partially Filled Dielectric Capacitors", TPT, Vol. 61, #6, Sept. 2023, p. 503.
  • Eric R. Dietz, "Force on a Dielectric Slab: Fringing Field Approach", AJP, Vol. 72, # 12, Dec. 2004, p. 1499.
  • F. N. Yan and H. K. Wong, "Force Between the Plates of a Parallel-Plate Capacitor", AJP, Vol. 61, #12, Dec. 1993, p. 1153.
  • S. Margulies, "Force on a Dielectric Slab Inserted into a Parallel-Plate Capacitor", AJP, Vol. 52, #6, June 1984, p. 515.
  • F. X. Hart and J. S. Massey, "Two Electrohydrodynamic Demonstrations", AJP, Vol. 49, #7, July 1981, p. 695.
  • Robert A. Morse, " # 4, The Flexible Capacitor: Connecting Electrostatics and Batteries", Teaching about Electrostatics, p. 4 - 5.
  • Robert A. Morse, "The Flexible Capacitor: An Electrostatic Demonstration Using Batteries", TPT, Vol. 30, #1, Jan. 1992, p. 22.


Disclaimer: These demonstrations are provided only for illustrative use by persons affiliated with The University of Iowa and only under the direction of a trained instructor or physicist.  The University of Iowa is not responsible for demonstrations performed by those using their own equipment or who choose to use this reference material for their own purpose.  The demonstrations included here are within the public domain and can be found in materials contained in libraries, bookstores, and through electronic sources.  Performing all or any portion of any of these demonstrations, with or without revisions not depicted here entails inherent risks.  These risks include, without limitation, bodily injury (and possibly death), including risks to health that may be temporary or permanent and that may exacerbate a pre-existing medical condition; and property loss or damage.  Anyone performing any part of these demonstrations, even with revisions, knowingly and voluntarily assumes all risks associated with them.