Force on an electron in a magnetic field

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SUMMARY

The force on an electron with a velocity of v = (2i – 3j) m/s in a magnetic field B = (0.8i + 0.6j – 0.4k) T is calculated using the equation F = qvBsinθ, resulting in a force of (1.92i + 1.28j + 5.77k) x 10^-13 N. The discussion highlights confusion regarding the sign of the force, as the electron's negative charge should theoretically yield a negative force vector. Participants emphasize the importance of showing work and verifying calculations with instructors to clarify any discrepancies.

PREREQUISITES
  • Understanding of the Lorentz force equation F = qvBsinθ
  • Knowledge of vector cross products in physics
  • Familiarity with magnetic fields and their properties
  • Basic principles of electromagnetism
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  • Review vector cross product calculations in electromagnetism
  • Study the implications of charge sign on force direction in magnetic fields
  • Learn about the behavior of charged particles in magnetic fields
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Students studying electromagnetism, physics educators, and anyone seeking to understand the dynamics of charged particles in magnetic fields.

chopnhack
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Homework Statement


What is the force on an electron with a velocity v = (2i – 3j) Mms-1 in a magnetic field B = (0.8i +
0.6j – 0.4k) T

Homework Equations


F=qvBsinθ

The Attempt at a Solution


using cross product I got: (1.92i + 1.28j + 5.77k)10^-13 N which is the listed correct answer.

My question is since this was an electron, why the value wasn't negative 1.92i, etc. Wouldn't the charge have contributed to the direction? Can someone please explain this to me?
Thanks
 
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The sign of q in the vector qvB contributes to the sign of the cross product answer...Can you show your work including the calculation of the cross product?
 
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berkeman said:
The sign of q in the vector qvB contributes to the sign of the cross product answer...Can you show your work including the calculation of the cross product?
sure
solution.jpg
 
Yeah, your work and your answer with the "-" signs looks right to me. You are saying that the "+" answer is listed as the correct answer?
 
berkeman said:
Yeah, your work and your answer with the "-" signs looks right to me. You are saying that the "+" answer is listed as the correct answer?
Yes, but the professor has been known to make mistakes.
 
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Does he/she have office hours before this is due? Show them your work and ask politely if you've missed anything...?
 
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berkeman said:
Does he/she have office hours before this is due? Show them your work and ask politely if you've missed anything...?
I have done just that. Hopefully I can get a clarification. It's very difficult to learn magnetism while correcting typos!
Thank you!
 
You're welcome. Just keep doing the math, and you should be fine. :smile:
 
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