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Electron Radius in a Bending Magnet

  • Thread starter mh1551
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  • #1
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Problem:

15 MeV electrons enter a bending magnet with a magnetic field of .7 tesla. What is the radius of the path of electrons?

Equation:

r = mV/Bq

B = .7 tesla
q = 1.6 x 10^-19 C

My problem here is that I don't know how to find the velocity of the electron for this equation. The supposed answer to the problem is 7.4 cm = r, but I'm just not getting that.
 

Answers and Replies

  • #2
vela
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With an energy of 15 MeV, the electrons are clearly relativistic. The formula you're using is only valid in the non-relativistic regime.
 
  • #3
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Do you know which equation I should be using then? This problem has been stumping me for days.

Thanks!
 
  • #4
vela
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That's something you should be able to derive on your own or at least find on your own in your textbook or notes.
 
  • #5
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I was told to use the equation above by my professor. That's why I'm confused now.
 

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