# Elementary Charge / Oil Drop clarification

1. May 22, 2007

### Lennox786

In an early set of experiments, Milikan observed that the following measure charges, among others, appeared at different times on a single oil drop. What value of elementary charge can be deduced from these data?

1) 6.563 x 10^-19 C
2) 8.204 x 10^-19 C
3) 11.50 x 10^-19 C
4) 13.13 x 10^-19 C
5) 16.48 x 10^-19 C
6) 18.08 x 10^-19 C
7) 19.71 x 10^-19 C
8) 22.89 x 10^-19 C
9) 26.13 x 10^-19 C

So what i was thinking is, that you would go #2 - #1 = elementary charge which in this case would come out to 1.641 x 10^-19 C.

And if you go #3 - #2, it would give you a mutiple of this elemtary charge. Which in this case would be 3.296 x 10^-19 C. Which is roughly a multiple of the elementary charge i got earlier because if you divide this by 2, you get 1.648 x 10^-19.

So do i keep doing that? then since each elementary charge I get is slightly off, then I just add up and take average?

2. May 22, 2007

### Chi Meson

Your reasoning is OK, but you can't assume that the difference between #2 and #1 is automatically the elementary charge. Furthermore there is nr rule that says you can only compare 3 with 2 and 4 with 3, etc.

Have you considered plotting the measurements on a graph? (well, more like on a numberline as there is no "y-axis" here).

3. May 22, 2007

### Lennox786

Ok. So how would i go about creating a chart and how would i find the elementary charge with this data?

4. May 22, 2007

### Chi Meson

Set up an "x axis" for charge such that you can plot with 4 sig figs, and put a dot on the axis for each charge you've got.

Then notice the spaces between the dots.