Clarifying the Basics of the Millikan Oil Drop Experiment

[sera97]

In the Millikan oil drop experiment, was the oil particles positively or negatively charged. and what were the charges of the plates. My textbook and what my gr.10 notes say is that the oil droplets and the bottom plate were positive, but every source online says that they were negative and that makes sense to me. Does it work either way? or have I been taught completely wrong?

 

[eigenperson]

The drops investigated could be either positive or negative, and the charge on the bottom plate could be either positive or negative, depending on which way he decided to put the battery.

In fact, Millikan writes, "On account of the slightly greater mobility of the negative ion, and also on account of the somewhat greater numbers in which they occur, we found, in general, a greater tendency of the drops to take up negative than positive charges. In view, therefore, of the greater ease with which negative drops could be held for long intervals without being lost to the plates most of the drops studied have been of negative sign." But his data includes drops with both types of charge.

 

[sera97]

Thank you!

 

[sophiecentaur]

I think it should be pointed out that it is the Field between the plates that you need to know and not the "charges". And PD divided by the spacing would give you that.

 

[pmacias]

The Millikan oil drop experiment is a fundamental experiment in physics that helped determine the charge of an electron. In this experiment, tiny oil droplets were suspended between two charged plates, and their motion was observed under the influence of an electric field.

Based on the original description of the experiment by Robert Millikan, the oil droplets were indeed negatively charged. However, it is possible that your textbook and notes have mistakenly labeled the droplets as positive. This could be due to a misunderstanding or a typographical error.

Regardless of the labeling, the important aspect of the experiment is the fact that the oil droplets were charged. This charge could be either positive or negative, as long as it was consistent and measurable. The charges of the plates, on the other hand, were opposite to that of the droplets in order to create an electric field and observe the motion of the droplets.

In science, it is important to critically evaluate information from different sources and confirm its accuracy. Therefore, it is possible that you have been taught incorrectly, but the important thing is to understand the concept and the results of the experiment. Both positive and negative charges can be used in the experiment, as long as the results are consistent and accurate.