Physics307L F09:People/Mahony/Millikan

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Millikan Oil Drop Lab Summary

In this lab, my partner Ryan and I recreated the famous Millikan Oil Drop experiment to find the charge of an electron. The procedure we "followed" is outlined in the Pasco Manual.

Results

We measured the charge for 7 droplets:

  • Droplet 1: 1.78(2) \cdot 10^{-13}C
  • Droplet 3: 2.01(2) \cdot 10^{-13}C
  • Droplet 4: 6.58(3) \cdot 10^{-14}C
  • Droplet 5: 5.81(2) \cdot 10^{-14}C
  • Droplet 6: 8.16(4) \cdot 10^{-14}C
  • Droplet 7: 6.68(3) \cdot 10^{-14}C
  • Droplet 8: 3.40(2) \cdot 10^{-14}C

These charges can be compared to the elementary charge of a single electron (from wikipedia):

e = 1.602176487(40) \cdot 10^{-19}C

See the Analysis section of the lab notebook for the calculation of the charges of each droplet.

Conclusions

After looking over the manual and other student's experiments I have concluded that Ryan and I did the lab wrong. For more info see the lab notebook. This could be the reason for our unexpectedly large results, or I may have made a mistake in my charge calculation that I simnply cannot find.

Despite having made a large mistake somewhere causing our data to become virtually meaningless, this lab was a good learning experience. In the future I will make sure I've read the manual correctly before starting. My suggestions for improving this lab include getting a brighter lamp for the Millikan apparatus, and finding a way to hook a CCD up to the optics, so you don't have to hunch over watching droplets for extended periods of time.

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