How to calculate magnitude of magnetic field

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SUMMARY

The discussion focuses on calculating the magnitude of a magnetic field (B) when electrons are accelerated through a potential difference of 2500V and move in a circular arc with a radius of 22cm. The key equation to derive B is F = Bqv, where F represents the centripetal force acting on the electrons. The kinetic energy gained from the potential difference can be used to determine the velocity (v) of the electrons, which is essential for calculating the magnetic field strength. The approach emphasizes the relationship between kinetic energy, radius, and magnetic force in classical electromagnetism.

PREREQUISITES
  • Understanding of classical mechanics, specifically centripetal force.
  • Knowledge of electromagnetism principles, particularly the Lorentz force.
  • Familiarity with kinetic energy calculations from potential difference.
  • Basic algebra for manipulating equations involving magnetic fields.
NEXT STEPS
  • Study the derivation of the Lorentz force equation, F = Bqv.
  • Learn how to calculate kinetic energy from potential difference in electron acceleration.
  • Explore the relationship between radius of circular motion and magnetic field strength.
  • Investigate the effects of varying magnetic fields on charged particles in motion.
USEFUL FOR

Students studying physics, particularly those focusing on electromagnetism and classical mechanics, as well as educators seeking to clarify concepts related to magnetic fields and charged particle dynamics.

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Homework Statement



Ill try to translate as good as possible.

Electrons are sent through potential difference of 2500V. Then they get into transverse magnetic field where they move in circular arc with 22cm radius. What is the magnitude of magnetic field?

So the radius is= 22cm
and the potential difference is 2500V.


Homework Equations



B= u0 I / 2 Pi r

I don't know how to calculate I out of this formula, so i can calculate B (magnitude of m.f.)

Or i have missed the solution to this problem completely? Please help
 
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Your equation is for calculating B from current, but in this question the B field is already there before the electrons went into, and this B field also accounts for the centripetal force which pulls the electrons into circular motion, provided the fact that the electrons have velocities after accelerated by the potential, and the B field is transverse.

So I guess the solving strategy is like this: get the kinetic energy of electrons from the 2500V potential difference, and together with the radius you can have the acceleration, just like we did in classical mechanics. Then the force F is obvious and B can be derived from F = Bqv.

I haven't touched EM for years, so cannot promise this answer is right.

Good luck.
 

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