Can (v1-v2) Prove the Existence of the Smallest Unit of Electric Charge?

In summary, the conversation discusses a recent lab where an animation of the oil drop experiment was used to find the velocity of a droplet in different directions of the applied forces. The difference in velocity (v1 - v2) was found and it was suggested that this could be used to prove the existence of a smallest unit of electric charge. However, it is noted that this would require multiple trials and accurate determination of the charge, Q. The conversation also mentions the importance of determining the mass of each droplet in the experiment. Overall, it is recognized as a clever experiment.
  • #1
Inquiring_Mike
50
0
We recently did a lab where we were given an animation of the oil drop experiment, and we were supposed to find the velocity of the droplet when Fg and FQ were in the same direction (v1) and when Fg and FQ were in opposite directions (v2)... Then we found (v1 - v2) and were told to analyze and prove the existence of a smallest unit of electric charge...
Here is the work I've done so far...

v1 (is directly proportional to) Fg + FQ
v2 (is directly proportional to) Fg - FQ

Therefore,
(v1 - v2) (is directly proportional to) (Fg + FQ) - (Fg - FQ)
(v1 - v2) (is directly proportional to) Fg -Fg + 2FQ
(v1 - v2) (is directly proportional to) 2FQ

Am I completely off track, can the fact that (v1-v2) is directly proportional to 2FQ be used to prove the existence of the smallest unit of electric charge?
 
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  • #2
The definate answer is ... maybe.

You need to do this many times. Each time, the charge, Q, will be different. If you accurately determine Q, you will eventually see that it is always an integral number times a smaller charge, q. If you are lucky, that smaller charge q=e (the charge on an electron). If you are not lucky, it might equal 2e, or 3e. As you do more trials, the chance of being unlucky becomes vanishingly small.

I always thought this was one of the cleverest experiments ever.

Njorl

edited to add- the nasty part is to determine the mass of each droplet.
 
Last edited:
  • #3
When I did the experiment, I found that (v1 - v2) was constant... Well pretty much, it fluctuated a little bit...
 

Related to Can (v1-v2) Prove the Existence of the Smallest Unit of Electric Charge?

1. What is Millikan's Oil Drop Experiment?

Millikan's Oil Drop Experiment was a landmark experiment in the field of physics conducted by Robert Millikan in 1909. It involved suspending tiny oil droplets in an electric field and measuring their motion to determine the charge of an electron.

2. How did Millikan conduct the experiment?

Millikan used a custom-made apparatus that consisted of a chamber with two parallel metal plates, an atomizer to create tiny oil droplets, and a light source to illuminate the droplets. He then introduced an electric field between the plates and observed the motion of the oil droplets using a microscope.

3. What were the results of Millikan's Oil Drop Experiment?

Millikan was able to determine the charge of an electron to be 1.602 x 10^-19 coulombs with a very small margin of error. He also confirmed that the charge of an electron is a fundamental constant and does not vary between particles.

4. Why is Millikan's Oil Drop Experiment significant?

Millikan's experiment provided the first accurate measurement of the charge of an electron and helped to establish the concept of quantized electric charge. It also provided evidence for the existence of subatomic particles and contributed to the development of the modern atomic model.

5. Are there any criticisms of Millikan's Oil Drop Experiment?

While Millikan's experiment was groundbreaking, it has faced some criticism for its use of statistical analysis and selection of data. Some have argued that the experiment was biased towards obtaining a specific result. However, the overall significance and impact of the experiment on the field of physics cannot be denied.

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