Physics307L F09:People/Mahony/Millikan
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: [math]\displaystyle{ 1.78(2) \cdot 10^{-13} }[/math]C
- Droplet 3: [math]\displaystyle{ 2.01(2) \cdot 10^{-13} }[/math]C
- Droplet 4: [math]\displaystyle{ 6.58(3) \cdot 10^{-14} }[/math]C
- Droplet 5: [math]\displaystyle{ 5.81(2) \cdot 10^{-14} }[/math]C
- Droplet 6: [math]\displaystyle{ 8.16(4) \cdot 10^{-14} }[/math]C
- Droplet 7: [math]\displaystyle{ 6.68(3) \cdot 10^{-14} }[/math]C
- Droplet 8: [math]\displaystyle{ 3.40(2) \cdot 10^{-14} }[/math]C
These charges can be compared to the elementary charge of a single electron (from wikipedia):
e = [math]\displaystyle{ 1.602176487(40) \cdot 10^{-19} }[/math]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.
