Electron Radius in a Bending Magnet

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Homework Help Overview

The discussion revolves around calculating the radius of the path of 15 MeV electrons in a bending magnet with a magnetic field of 0.7 tesla. The original poster attempts to apply the formula r = mV/Bq but is uncertain about determining the velocity of the electrons due to their relativistic nature.

Discussion Character

  • Exploratory, Assumption checking

Approaches and Questions Raised

  • Participants discuss the applicability of the original formula in a relativistic context and question the appropriate equations to use for calculating the velocity of relativistic electrons.

Discussion Status

Some participants have pointed out the need for a different approach due to the relativistic speeds of the electrons, while the original poster expresses confusion about the guidance received from their professor. The conversation indicates a lack of consensus on the correct method to apply.

Contextual Notes

The original poster mentions being instructed to use a specific equation by their professor, which adds a layer of complexity to their understanding of the problem.

mh1551
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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.
 
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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.
 
Do you know which equation I should be using then? This problem has been stumping me for days.

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

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