Clarifying the Basics of the Millikan Oil Drop Experiment

In summary, the Millikan oil drop experiment investigated both positively and negatively charged oil particles. The charge on the bottom plate could also be either positive or negative, depending on the setup of the battery. Millikan's data shows a greater tendency for the drops to have negative charges. It is important to note that the focus should be on the electric field between the plates, rather than the specific charges. The potential difference divided by the spacing can determine the electric field.
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sera97
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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?
 
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  • #2
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.
 
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Thank you!
 
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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.
 
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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.
 

1. What is the purpose of the Millikan Oil Drop Experiment?

The purpose of the Millikan Oil Drop Experiment is to determine the charge of an electron by measuring the rate at which charged oil drops fall in an electric field. This allowed for the first accurate measurement of the charge of an electron.

2. How does the Millikan Oil Drop Experiment work?

In this experiment, tiny oil droplets are sprayed into a chamber with a known electric field. The drops become charged due to friction with the air, and their motion is observed under a microscope. By adjusting the electric field, the rate of fall of the drops can be controlled and used to calculate the charge on each droplet.

3. What was Robert Millikan's contribution to the Millikan Oil Drop Experiment?

Robert Millikan was a physicist who designed and conducted the Millikan Oil Drop Experiment in 1909. He developed a method for suspending oil droplets in midair using an electric field and measured the rate at which they fell. This allowed him to calculate the charge of each droplet and ultimately determine the charge of an electron.

4. What were the results of the Millikan Oil Drop Experiment?

Through his experiments, Millikan found that the charge on each oil droplet was always a multiple of a single, fundamental unit of charge, which he concluded was the charge of an electron. He determined this charge to be 1.602 x 10^-19 coulombs, which is still accepted as the most accurate measurement of the electron's charge today.

5. How did the Millikan Oil Drop Experiment impact our understanding of atomic structure?

The Millikan Oil Drop Experiment provided the first accurate measurement of the charge of an electron and helped confirm the existence of individual, discrete charges. This was a key step in developing the modern understanding of atomic structure and the concept of the atom as consisting of smaller subatomic particles.

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