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2009 Advanced Laboratories Conference Abstract Detail Page

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Abstract Title: Millikan’s Oil Drop: Simulation and Experiment
Abstract: In our Advanced Laboratory and Computational Physics course, students combined numerical and experimental methods to study the historic Millikan oil drop experiment which revealed the charge of a single electron. Both the experiment and numerical model were relatively simple, however students benefited from the variety of skills and analysis techniques used to study the same system with two different methods. In the experiment, an oil drop apparatus (purchased from PASCO) allowed the motion of charged oil drops to be observed as they moved in the presence and absence of an external electric field. Gravitational and drag forces also acted on the moving drops, and terminal velocities of each drop were determined by observing motion over long times. Through the application of Stokes Law, the elementary charge of a single electron was deduced. In the numeric approach to the oil drop system, the forces on a single drop were calculated using prescribed values for mass, charge, and electric field. The motion of a single oil drop was simulated using FORTRAN by calculating the resulting acceleration, velocity, and position of the droplet in time. Modeling the drag force introduced complexity to the model, as drag force depends on velocity, thus acceleration varies until terminal velocity is reached. The model allowed microsecond-scale transient times to be studied before terminal velocity was reached, and provided results to compliment the data collected experimentally. Visualization software was also used to illustrate the data produced by the mathematical model.
Abstract Type: Poster
Contributed Poster: Download the Contributed Poster
Session: Session IX - Effective Experiments Poster Session

Author/Organizer Information

Primary Contact: Sarah J Desotell
Ripon College
300 Seward Street
PO Box 248
Ripon, WI 54971