1
$\begingroup$

I had a question about the Millikan Oil drop experiment. I did the experiment for my physics class where we had to determine the voltage that would make the droplet stationary. We did this ten times, so I have ten different voltages. The mass, gravity, and distance remains the same it is only the voltage that is changing. The part I am struggling with is, I must determine my own fundamental charge from this experiment and compare it to the accepted value of 1.6x10^-19. How do I determine my own fundamental charge when I am given 10 different voltages? I believe that I am supposed to use the q=mgd/V equation but I am not fully sure. My mass is: 1.57x10^-15 C My distance: 0.1 m Gravity: 9.81 m/s^2 My voltages: 400, 457, 384, 369, 400, 355, 369, 436, 384, and 369.

$\endgroup$
6
  • $\begingroup$ Have you tried calculating q for each of your values of V? $\endgroup$ – Daddy Kropotkin Dec 12 '20 at 23:11
  • $\begingroup$ Yes, I calculated all of the q values for V. $\endgroup$ – Lulu Dec 12 '20 at 23:18
  • $\begingroup$ Were those q values mostly near $1.6\times10^{-19}$ C, $2 \times 1.6\times10^{-19} $ C, ... ? Or perhaps were they near $some value$, $2 \times some value$, ...? $\endgroup$ – mmesser314 Dec 12 '20 at 23:57
  • $\begingroup$ They were not. They were actually around values like, 3.37x10^-18 C all the way to 4.17x10^-18 C. I calculated the differences between all the charges and then I got values around 1.6x10^-19 C to 4.9x10^-19 C. $\endgroup$ – Lulu Dec 13 '20 at 0:03
  • $\begingroup$ The smallest non-zero difference between your calculations should be due to only 1 electron. $\endgroup$ – David White Dec 13 '20 at 0:33
2
$\begingroup$

It appears that your measurements may have been very imprecise. However, given your data, the best approach is to find a value for e such that the RMS differences between the charges $q_i$ you found and the nearest values of $n_i e$ to the $q_i$ is minimized. That is, minimize the square root of the sum of the squares of $(n_i e -q_i)^2$ by fiddling with the value of $e$. Choose $n_i$ for each $q_i$ so that $n_i e$ is as close as possible to $q_i$. Easy to do in a spreadsheet.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.