Calculating E/M for Helmholtz Coils -- help please

AI Thread Summary
The discussion revolves around calculating the charge-to-mass ratio (e/m) for electrons using data from a Helmholtz coil experiment. The original poster encountered a discrepancy between their calculated value of 1.96 x 10^11 Coulombs/kg and the accepted value of 1.76 x 10^11 Coulombs/kg, suspecting a potential unit error. They realized that they may have calculated in Coulombs per kg instead of abcoulombs per kg, which could explain the difference. After reviewing their measurements and calculations, the poster confirmed that their professor accepted their results, indicating that their approach was ultimately correct. The conversation highlights the importance of unit consistency in scientific calculations.
grandpa2390
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edit: wait... I think the discrepancy is that I calculated Coulombs per kg? and the accepted value I was looking at was in abcoulombs per kg. If that is indeed the case, then my answer is indeed close to the accepted value of 1.76 * 10^11 Coulomb/kg. 1. Homework Statement
I am trying to calculate e/m for data I got from a laboratory experiment with a helmholtz coils. I am not sure if I have bad data, or if I have a mistaken unit somewheres. I am getting 1.96 * 1011 after I average all my e/m together. I should be getting 1.76 * 107

Am I doing something wrong, or is it my data? I am not going to put all my data up. I will just put some 1 measurement and please tell me if I am using wrong units somewheres.

Homework Equations


http://badger.physics.wisc.edu/lab/manual2/node10_tf.html

e/m = [PLAIN]http://badger.physics.wisc.edu/lab/manual2/img129.gif2.47 x 1012[PLAIN]http://badger.physics.wisc.edu/lab/manual2/img130.gif[PLAIN]http://badger.physics.wisc.edu/lab/manual2/img131.gif[PLAIN]http://badger.physics.wisc.edu/lab/manual2/img132.gif coulombs/kg

The Attempt at a Solution



my measurement is:

accelerated voltage = 40 volts
current for helmholtz coils = 2.46 Amps
Radius of coil = .33 meters
there are 72 turns on each coil
radius of the electron beam = .039 meters

I get 2.25 * 10^11
is this what my data gives me, or am I using the formula incorrectly? I should get 10^7
 
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Thanks for the post! Sorry you aren't generating responses at the moment. Do you have any further information, come to any new conclusions or is it possible to reword the post?
 
no worries. I went ahead and went with what I had. It must have been correct, my professor accepted it.
 

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