Demonstrations

Millikan Oil Drop Experiment

Code Number :	7A15.10
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 :	Charge of the Electron
Area of Study :	Modern Physics
Equipment :	Goose Neck Video Camera, Millikan Oil Drop Unit, 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.

Web Sites

QuickTime Movie:

http://www.britannica.com/nobel/cap/omillik001a4.html

Simple Simulation: http://webphysics.davidson.edu/applets//pqp_preview/contents/pqp_errata

and then click on "Section 4.5".

References

Anthony Papirio, Jr., Claude M. Pemchina, 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.

Haym Kruglak, "Magnitude of Electronic Charge with the PSSC Millikan Apparatus", TPT, Vol. 6, # 9, Dec. 1968, p. 477.

Mario Iona, "Magnitude of Electronic Charge", TPT, Vol. 7, # 5, May. 1969, p. 302.

Haym Kruglak, "The Author Reply", TPT, Vol. 7, # 5, May 1969, p. 303.

Kenneth J. Silva, Jacquelyn C. Mahendra, "Digital Video Microscopy in the Millikan Oil-Drop Experiment", AJP, Vol. 73, # 8, Aug. 2005, p. 789.

C. N. Wall, F. E. Christensen, "Dual-Purpose Millikan Experiment with Polystyrene Spheres", AJP, Vol. 43, # 5, May 1975, p. 408.

J. I. Kapusta, "Best Measuring Time for A Millikan Oil Drop Experiment", AJP, Vol. 43, # 9, Sept. 1975, p. 799.

Mark A. Head, "Millikan Oil-Drop Experiment in the Introductory Laboratory", AJP, Vol. 42, # 3, March 1974, p. 244.

B. Spenceley, L. Hastigs, "Laser Illumination for the Millikan Oil-Drop Experiment", AJP, Vol. 40, # 3, Mar. 1972, p. 474.

Haym Kruglak, "Another Look at the Pasco-Millikan Oil-Drop Apparatus", AJP, Vol. 40, # 5, May 1972, p. 768.

Michael F. Perry, "Remembering the Oil-Drop Experiment", Physics Today, May 2007, p. 56.

Robert P. Crease, "Seeing The Electron: Millikan's Oil-Drop Experiment", The Prism & The Pendulum, Ch. 8, p. 144 - 162.

Mail Questions and Comments to: Dale Stille