Physics307L:People/Cochran/E-m ratio

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complete setup

In this lab, we measured the mass-to-charge ratio of the electron by measuring the radii of electron beams at different currents and voltages. We used Hewlett Packard DC Power Supply (Model 6384A, 4-5.5V, 0-8A), an e/m experimental apparatus (Model TG-13), a SOAR corporation DC Power Supply (Model 7403, 0-36V, 3A), and a Gelman Instrument Company Deluxe Regulated Power Supply (500V, 100mA).

notebook entry


We calculated the charge-to-mass ratio to be e/m = 1.539391 +/- 0.0261801*1011, with a percent error of %error = 12.351%.

SJK 22:46, 21 December 2010 (EST)

22:46, 21 December 2010 (EST)
Again, missing is a comparison of the discrepancy from accepted value, relative to the SEM, and leading into a discussion of systematic error.


The large percent error in this experiment is, I believe, due to the extreme difficulty we had in accurately reading the radius measurement using the mirror setup. However, our result was still in the same order of magnitude as the accepted result, which I think shows that our procedure was not intrinsically flawed. Perhaps having taken more measurements would have eliminated some of this error.