5B10.40 - Electric Field Lines Demo

Code Number:
Demo Title:
Electric Field Lines Demo
Electric Field Lines of Force
Area of Study:
Electricity & Magnetism
Castor Oil, Felt Powder, Petri Dishes, Electrodes (Assorted), 5 kV Power Supply, Overhead Projector, Mustard Seed Slides, Flexcam and Slide Viewer, and Overhead Projector with Attached Magnifying Lens.

The oil used is castor oil.  There is a plastic bottle that has the oil and felt in it already in the proper mixture.  Stir this up several times at least 1/2 hour ahead of time to allow the air bubbles to settle out.

The felt will settle out some but not enough to affect the demonstration.  Pour the mixture into a petri dish and add the desired bars or point sources.  Touch the wire electrodes to these and apply the voltage from the 5 KV power supply.  The felt will align itself to show the lines of force around the bars or points.  Use only as much voltage as necessary and then turn it off as boiling and worse will come about if the voltage is left on.

There is a set of 6 Mustard Seeds In Oil Slides that show these lines of force also that may be used in conjunction with this demo.

NOTE: Use wool felt, not synthetic felt.

  • Francisco Vera, Manuel Ortiz, Rodrigo Rivera, Francisco Antonio Horta-Rangel, "Visualizing Electric Fields Using Rubbed Balloons as the High-Voltage Source", TPT, Vol. 62, #2, Feb. 2024, p. 93.
  • James Lincoln, "Electric Field Patterns Made Visible with Potassium Permanganate", TPT, Vol. 55, #2, Feb. 2017, p. 74.
  • Jeffrey A. Phillips, Jeff Sanny, David Berube, and Anatol Hoemke, "Beyond the Point Charge: Equipotential Surfaces and Electric Fields of Various Charge Configurations", TPT, Vol. 55, #2, Feb. 2017, p. 71.
  • Thomas D. Rossing, "Magnetic Images and J.C. Maxwell", TPT, Vol. 29, #5, May 1991, p. 262.
  • Raymond E. Benenson, "Demonstration of Magnetic Images", TPT, Vol. 29, #1, Jan. 1991, p. 54.
  • Barbara S. Andereck, "Using Contour Maps to Teach Electric Field and Potential", TPT, Vol. 27, #7, Oct. 1989, p. 499.
  • Richard S. Murphy and Charles Montefusco, "Electric Field and Gaussian Models", TPT, Vol. 27, #5, May 1989, p. 400.
  • George A. Dulk and Robert Stoller, "Electric Fields and Electromagnetic Waves", TPT, Vol. 19, #1, Jan. 1981, p. 50.
  • Lowell Knoop and Oleg Jefimenko, "Electric Fields in Conductors", TPT, Vol. 15, #1, Jan. 1977, p. 52.
  • Ian Mennie and Cyril Snook, "Electric Field Using an Overhead Projector", TPT, Vol. 13, #9, Dec. 1975, p. 558, also A Potpourri of Physics Teaching Ideas - Electricity and Magnetism, p. 150.
  • Tomoyoshi Kittaka, "Lines of Force of an Electric Field by Electromigration of Ions", TPT, Vol. 8, #3, Mar. 1970, p. 143.
  • Michael Bernstein, "Making an Electric Field Visible with KMnO4 Crystals", TPT, Vol. 7, #5, May 1969, p. 301.
  • Mike Weiss and Herbert H. Gottlieb, "Shape of an Electric Field", TPT, Vol. 5, #6, Sept. 1967, p. 286, also A Potpouri of Physics Teaching Ideas - Electricity and Magnetism, p. 156.
  • Ross L. Spencer, "Electric Field Lines Near an Oddly Shaped Conductor in a Uniform Electric Field", AJP, 56, #6, June 1988, p. 510.
  • Rainer Weiss, B. Molnar, and J. W. Davisson, "Demonstration of Electrostatic Field Lines and Distributions", AJP, Vol. 39, #3, Mar. 1972, p. 350.
  • "E-065. Velveteens and Grass Seed", DICK and RAE Physics Demo Notebook, 1993.
  • G. D. Freier and F. J. Anderson, "Eb-1", A Demonstration Handbook for Physics.
  • David Kutliroff, "78. Lines of Force", 101 Classroom Demonstrations and Experiment For Teaching Physics, p. 171.
  • Robert Ehrlich, "L.5. Mapping the Electric Field", Turning the World Inside Out and 174 Other Simple Physics Demonstrations, p. 148 - 149.
  • Neil. A. Downie, "Follow that Field", Ink Sandwiches, Electric Worms and 37 Other experiments for Saturday Science, p. 79.
  • Tom Petruzzellis, "Electric Fields", Electronic Sensors for the Evil Genius, p. 198.
  • Sara Stein, "The Shape of Space", The Science Book, p. 237.
  • Keithley Instruments, "Physics Experiment #6: The Electric Field", Series I.
  • W. Bolton, "8. Electric Lines of Force", Book 4 - Electricity, Physics Experiments and Projects, 1968, p. 17 - 18. 

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.