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M o d e l N o . A P - 8 2 1 0 A
Few experiments that are so simple in principle have provided such a wealth of experimental evidence to confirm
the atomic theory and measure an important physical constant.
Suggested Reading
Should the student desire a more detailed back ground in this classic experiment, the following references are sug-
gested:
1. Millikan, Robert A., The Electron, (Chicago, The University of Chicago Press, 1917 (reprinting in paperback
form, 1963).
2. Millikan, Robert A., "The Isolation of an Ion, A Precision Measurement of its Charge, and the Correction of
Stokes' Law," The Physical Review, Vol. 2, No. 2, pp. 109 – 143, June 1913.
3. Millikan, Robert A., "On the Elementary Electrical Charge and the Avogadro Constant," The Physical Review,
Vol. 32, No. 4, pp. 349 – 397, April, 1911.
4. Shamos, M.H., Great Experiments in Physics (Holt-Dryden, New York, 1959), pp. 238 – 249.
Maintenance Notes
Cleaning
1.
The housing of the droplet viewing chamber, the capacitor plates, the plastic spacer, and the droplet hole cover
should be cleaned with water and detergent, with particular attention to the droplet hole in the top capacitor
plate, the glass observation port covers on the housing, and the droplet hole cover.
2.
The plastic spacer should be polished with a soft, lint-free cloth to remove any oil, finger prints, or lint.
3.
The lens on the plastic spacer should be cleaned on both sides using a cotton-covered tip ("Q-tip").
4.
Apply a thin film of oil to the capacitor plates to help prevent corrosion.
5.
Dry all parts completely before reassembly.
Always handle the plastic spacer and capacitor plates carefully to avoid scratching them.
Solvents that might attack the plastic should be avoided
Adjusting vertical reticle and viewing scope alignments
If the alignment of the reticle or viewing scope is altered during rough handling, realign it using the following pro-
cedure:
1.
Loosen the set screw in the viewing scope holder (Figure 12).
2.
With the focusing wire in place and while looking through the eye-
piece, rotate the viewing scope until the vertical reticle lines are
vertical to the focusing wire.
3.
Find the center of focus in the adjustment knob on the viewing
scope (this will be approximately half-way between minimum and
maximum focus).
4.
Manually move the viewing scope in and out through its holder
until the focusing wire comes into focus.
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0 1 2 - 1 3 0 9 3 B
M a i n t e n a n c e N o t e s
set screw
Figure 12: Viewing scope set screw
17
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