# Millikan's oil drop experiment

• cindy!
In summary, the task was to analyze the charge and number of excess electrons on an oil drop using 5 different electric fields. Through calculations, the charge was found to be 3.63x10^-19, 3.16x10^-19, 2.73x10^-19, 2.45x10^-19, and 31.89x10^-19, and the number of excess electrons was found to be 2.27e, 1.97e, 1.7e, 1.53e, and 1.18e. However, the results may not be entirely accurate due to potential sources of error. The teacher's advice is to not ignore any data points
cindy!

## Homework Statement

hello, our task was to go on to this site http://www.wcsyearbooks.com/millikan/experiment.html and then figure out the charge and the number of excess electrons on the oil drop using 5 electric fields.
Electric field: 2.7x10^4, 3.1x10^4, 3.6x10^4, 4.0x10^4 and 5.2x10^4
m=1.0 x10-15 kg
g is -9.8 m/s2.

## Homework Equations

for charge: q=mg/E
found that q= 3.63x10^-19, 3.16x10^-19, 2.73x10^-19, 2.45x10^-19 and 31.89x10^-19

for number of excess electrons: N=q/e
found that e= 2.27e, 1.97e, 1.7e, 1.53e and 1.18e

however this does not seem right but is is just simple calculations with most of the data given to me...

## The Attempt at a Solution

i sort of did it up there i just didnt show the esact calcualtions because it is simple math but the thing i don't understand is whether or not the drops have an integer of excess electrons..if it did wouldn't N be a whole number?

thanks for any help.

Last edited by a moderator:
Thats the supreme brilliance of the experiment--it should be an integer number. But given the difficulty of this experiment, I bet if you ran 100 oil droplets thru 5 voltages, they would start to cluster around n's. The one that outlies here is the 1.53. But 5 trials might be increased with better results. Can you do 5 for each 5 fields?

im not sure if we are allowed to do that since she only asked for five but ill probably include a sources of error and put that down.

I talked to my teacher this morning and she said she wasnt worried about the numbers that we discovered just as long as we are able to explain why it is incorrect. But that's where I am confused..how is it possible to be wrong? If one of my numbers were an integer i couldn't ignore the other four...

Last edited:
Now that would be the supreme mistake, you get one in 5 you like, ignore the rest. I understand the temptation. But you need to keep from imposing your wishes on the data set. You could do 5 trials and have one come up out to
.99 or 1.02 and sieze on that when the true value is 1.3. Mendel who figured out the rudiments of genes did exactly that.

And your teachers answer shows great insight as well--don't throw out the beby with the bathwater. All measurements and sampling are prone to error. Understand the size and source.

## What is Millikan's oil drop experiment?

Millikan's oil drop experiment is a famous physics experiment performed by Robert Millikan in 1909 to determine the charge of an electron. It involved observing the motion of tiny oil droplets in an electric field and measuring their charge using the principles of electrostatics.

## Why is Millikan's oil drop experiment important?

Millikan's oil drop experiment was important because it provided the first direct measurement of the charge of an electron, which was a fundamental constant in physics. It also confirmed the existence of individual charged particles and their quantized nature.

## How was Millikan's oil drop experiment conducted?

Millikan's oil drop experiment involved suspending tiny oil droplets between two charged plates and observing their motion under the influence of an electric field. By adjusting the electric field and measuring the droplets' motion, the charge of the droplets could be calculated and used to determine the charge of an electron.

## What were the results of Millikan's oil drop experiment?

Millikan's oil drop experiment determined the charge of an electron to be 1.602 x 10^-19 coulombs, which is very close to the currently accepted value. This experiment also provided evidence for the quantized nature of electric charge and helped to confirm the existence of individual charged particles.

## What is the significance of Millikan's oil drop experiment in modern physics?

Millikan's oil drop experiment is considered a groundbreaking experiment in modern physics because it provided the first direct measurement of the charge of an electron, which is a fundamental constant in many areas of physics. It also paved the way for further experiments and discoveries in the field of subatomic particles.

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