Magnitude of force on electron in magnetic field

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Homework Help Overview

The problem involves an electron that has been accelerated by a voltage and then enters a magnetic field. The focus is on determining the magnitude of the force acting on the electron due to the magnetic field, utilizing the relationship between charge, velocity, and magnetic field strength.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • The original poster attempts to understand how to calculate the velocity of the electron from the given voltage, expressing uncertainty about its relevance. Some participants suggest using energy equations to find the velocity, while noting the conversion from electron volts to joules. Others mention the need for relativistic corrections due to the electron's speed.

Discussion Status

The discussion is ongoing, with participants providing guidance on how to relate the voltage to kinetic energy and subsequently to velocity. There is acknowledgment of the need for relativistic considerations, indicating a productive exploration of the problem.

Contextual Notes

Participants are navigating the implications of the initial voltage and its role in determining the electron's velocity, while also considering the effects of relativistic speeds on calculations.

jaydnul
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Homework Statement


An electron in a vacuum is first accelerated by a voltage of 41300 V and then enters a region in which there is a uniform magnetic field of .145 T at right angles to the direction of the electron's motion.

What is the magnitude of the force on the electron due to the magnetic field?

Homework Equations


F=qvBsinθ

The Attempt at a Solution


At first I though the 41300 V was just a number to throw me off (they do that a lot), but now I think it is important. I know the charge, magnetic field, and sin90=1. So the only thing I'm missing is velocity, but I have no clue how to calculate that from the information I was given. Any help?

Thanks
 
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You can find the energy of an electron by using qV = U, where U is the Kinetic Energy of the particle. Then it's just a matter of solving for v from the KE equation.

EDIT: I should point out that the energy will be in eV, which you can then just use a conversion factor to get it into joules.
 
The electron is moving fast enough to warrant relativistic correction for calculating the velocity.
 
Perfect. Thanks
 

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