# AUS- Needing a abit of help

1. May 15, 2006

### ekinnike

This question is in my yr 12 homework textbook.

q21.keyword e=exponential in case if i confused u .
In a tube similar to that used in the Thomson's electromagnetic experiment, a magnetic of 1.00 x 10e-2 T is sufficient to allow the electrons to pass through the electric delfection plates. The plates are 10 mm apart and have a potential difference of 300 V across them.
(a) what is the strength of the electric field between the plates? 3x10e4 vm(i did and checked with the book)no problem with this question...

(b)What was the speed of the lectrons as they entered the region between the plates? working on...
(c) what was the strength of the magnetic force acting on the electrons.
havent try
i only have some formulas to work with it
F = qvBsinO v=velocity

E = V/d V=voltage

v= B/E <--- not quite sure about this .i tried to apply for (b) but didnt quite get the answer. I have answer at the back of book but i cant work it out...
thanks in advanced

2. May 15, 2006

### Staff: Mentor

I'm not familiar with Thomson's electromagnetic experiment. Could you provide a link to a diagram? You are correct that you need the velocity v from answer (b) in order to calculate the magnetic force F=qvXB.

3. May 16, 2006

### ekinnike

http://library.thinkquest.org/13394/angielsk/athompd.html <-- i just googled it. not sure if it useful

Last edited by a moderator: Apr 22, 2017
4. May 16, 2006

### Staff: Mentor

Well, it certainly looks like there is enough info in that link to help you solve your homework problem. Especially the explanation and equations about 3/4 of the way down. Don't they help you with question (b) about the required velocity...?

Last edited by a moderator: Apr 22, 2017
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