7A15.10 - Millikan Oil Drop Experiment

Code Number:
7A15.10
Demo Title:
Millikan Oil Drop Experiment
Condition:
Good
Principle:
Charge of the Electron
Area of Study:
Modern Physics

Disclaimer

Equipment:
Goose Neck Video Camera, Millikan Oil Drop Unit, and Latex Spheres in Solution.
Procedure:

Align the goose neck camera to the eye piece of the microscope so that the scale is in sharp focus.  Squeeze the bulb and introduce a mist of latex spheres into the chamber.  Many bright dots should appear.  Apply the potential voltage to the two plates in the chamber.  Some of the bright dots should appear to move upwards apposing gravity.  Of these that move pick one that is brightest in the microscopes field of view.  By reducing the voltage to zero you should be able to time the dots fall between the lines on the scale.  By applying a voltage you should make the dot move upward at a rate that is proportional to the voltage applied.  This upward motion can also be timed.  The radius for the latex spheres should be on the order of 5.5 X 10-7 m.  With this and knowing the voltage applied, the time to rise or fall the scaled division, the charge of the electron can be calculated.

If done carefully the calculations should come close to the 1.602 X 10-19 coulomb excepted value.

References:
  • William M. Wehrbein, "Millikan Again", TPT, Vol. 60, #4, April 2022, p. 299.
  • Isabel Bishop, Siyu Xian, and Steve Feller, "Correction: Robert A. Millikan and the Oil Drop Experiment", TPT, Vol. 59, #4, April 2021, p. 227.
  • Isabel Bishop, Siyu Xian, and Steve Feller, "Robert A. Millikan and the Oil Drop Experiment", TPT, Vol. 57, #7, Oct. 2019, p. 442.
  • William M. Wehrbein, "Millikan Drop on Film", TPT, Vol. 50, #4, Apr. 2012, p. 198.
  • Michel Gagnon, "Millikan's Oil-Drop Experiment: A Centennial Setup Revisited in the Virtual World", TPT, Vol. 50, #2, Feb. 2012, p. 98.
  • Lowell I. McCann and Earl D. Blodgett, "The ‘Nut-Drop‘ Experiment—Bringing Millikan's Challenge to Introductory Students", TPT, Vol. 47, #6, Sept. 2009, p. 374.
  • Xueli Zou, Eric Dietz, Trevor McGuire, Louise Fox, Tiara Norris, Brendan Diamond, Ricardo Chavez, and Stephen Cheng, "Millikan Movies", TPT, Vol. 46, #6, Sept. 2008, p. 365.
  • Anthony Papirio Jr., Claude M. Penchina, and Hajime Sakai, "Novel Approach to the Oil-Drop Experiment", TPT, Vol. 38, #1, Jan. 2000, p. 50.
  • Mark Vondracek, "Electrical Analog to Projectile Motion", TPT, Vol. 36, #4, Apr. 1998, p. 224.
  • Steve Brehmer, "Millikan Without the Eyestrain", TPT, Vol. 29, #5, May 1991, p. 310.
  • Arun C. Venkatachar, "Determination of the Electronic Charge—Electrolysis of Water Method", TPT, Vol. 23, #6, Sept. 1985, p. 365.
  • Bob Kimball, "Two New Experiments", TPT, Vol. 11, #6, Sept. 1973, p. 353, also A Potpourri of Physics Teaching Ideas - Odds and Ends, p. 322.
  • Mario Iona, "Magnitude of Electronic Charge", TPT, Vol. 7, #5, May. 1969, p. 302.
  • Haym Kruglak, "The Author Replies", TPT, Vol. 7, #5, May 1969, p. 303.
  • Haym Kruglak, "Magnitude of Electronic Charge with the PSSC Millikan Apparatus", TPT, Vol. 6, #9, Dec. 1968, p. 477.
  • Kenneth J. Silva and Jacquelyn C. Mahendra, "Digital Video Microscopy in the Millikan Oil-Drop Experiment", AJP, Vol. 73, #8, Aug. 2005, p. 789.
  • Ray C. Jones, "The Millikan Oil-Drop Experiment: Making it Worthwhile", AJP, Vol. 63, #11, Nov. 1995, p. 970.
  • William M. Fairbank Jr. and Allan Franklin, "Did Millikan Observe Fractional Charges on Oil Drops", AJP, Vol. 50, #5, May 1982, p. 394.
  • J. I. Kapusta, "Best Measuring Time for A  Millikan Oil Drop Experiment", AJP, Vol. 43, #9, Sept. 1975, p. 799.
  • C. N. Wall and F. E. Christensen, "Dual-Purpose Millikan Experiment with Polystyrene Spheres", AJP, Vol. 43, #5, May 1975, p. 408.
  • Mark A. Head, "Millikan Oil-Drop Experiment in the Introductory Laboratory", AJP, Vol. 42, #3, Mar. 1974, p. 244.
  • Haym Kruglak, "Another Look at the Pasco-Millikan Oil-Drop Apparatus", AJP, Vol. 40, #5, May  1972, p. 768.
  • B. Spenceley and L. Hastigs, "Laser Illumination for the Millikan Oil-Drop Experiment", AJP, Vol. 40, #3, Mar. 1972, p. 474.
  • Guenter Schwarz and Haym Kruglak, "Suggestions for the Pasco Millikan Oil Drop Apparatus", AJP, Vol. 36, #12, Dec. 1968, p. 1169, also Apparatus Notes, July 1965-December 1972, p. 82.
  • H. Victor Neher, "Changing the Charge on the Drop in Millikan Oil Drop Apparatus", AJP, Vol. 34, #2, Feb. 1966, p. xv, also Apparatus Notes, July 1965-December 1972, p. 15.
  • Byron D. Bottoms and James E. Faller, "A Convenient Method for Changing the Charge in the Millikan Oil-Drop Experiment", AJP, Vol. 33, #5, May 1965, p. 411.
  • Michael F. Perry, "Remembering the Oil-Drop Experiment", Physics Today, Vol. 60, #5, May 2007, p. 56.
  • Robert P. Crease, "Seeing The Electron: Millikan's Oil-Drop Experiment", The Prism & The Pendulum, Ch. 8, p. 144 - 162.
  • L. Neel Beard and Edward M. Keiss, "Physics Experiment #3 (Series II): The Charge of an Electron", Keithley Instruments.
  • W. Bolton, "2. The Charge on the Electron", Book 3 - Atomic Physics, Physics Experiments and Projects, 1968, p. 5 - 8.
Millikan Movies from CSU Chico:
Simple Simulation (Click on section 45)
Britannica - Winners of the Nobel Prize

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.