Can someone explain how Milikan isolated the electron's weight?

Factual Questions
1

The only thing in our textbook about him was that he isolated the
wiegth of the electron, but I was wondering how you would get
the specific wieght of somthing that small. Any one wanta explain
an expiriment or theory?
=Pk

2

Is this for homework?

3

First, Millikan measured the charge “e” of an electron using the oil drop experiment. There is a separate experiment to find “e/m”, the ratio of charge to mass of an electron. Since the charge is known from the oil drop experiment, then you can find the mass. This second exp. (at my college) involved sending electrons down a tube which was wrapped in wire to produce a magnetic field. The field caused the electrons to spiral down. By finding the length of the spiral, the size of the magnetic field, etc., you get e/m.

4

My understanding is that it was an indirect approach: He weighed a large number of charged oil droplets of various sizes, very accurately, then looked for a mass of which each droplet’s charged-vs.-uncharged mass difference would be an integral multiple.

5

what ftg said… he isolated the electron’s charge

and IIRC, the weight of the oil droplets in his experiment could be figured out by their rate of fall (their terminal velocity)

6

The weight of the drops could be found by their terminal velocity, as noted. And their charge/weight (hence charge) by the size of the electric field required to suspend them in midair. When the charges all turned out to be multiples of something, that something (which I believe was actually found on some drops) was deduced to be the charge on one electon. Very simple and very elegant!

7

The mass of the electron can be determined as an output of the cathode ray experiments of J.J. Thompson.

Thompson used an equation for ratio of e/m that included the velocity. He then measured the velocity by balancing electric and magnetic deflections of the beam in a cathode ray tube. He found that the ratio e/m for an electron is 1836 times that for a hydrogen ion. The masses of the hydrogen atom and the hydrogen ion were known and known to be nearly the same, it follows that the mass of the electron is 1/1836 the mass of a hydrogen atom, which was known.

Millikan measured the charge on the electron.