Confused about electric field/velocity/magnetic field vectors

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SUMMARY

The discussion centers on the relationship between electric field (E), velocity (v), and magnetic field (B) vectors, specifically the equation E = v × B. A user presents a scenario with v = 5j and B = -1k, leading to confusion about the direction of E. The conversation clarifies that E = -v × B in the context of electromagnetic waves and emphasizes the importance of the right-hand rule for determining the direction of force (F = qv × B). The discussion concludes that E can indeed be in the positive i direction under specific conditions, but the user must consider the presence of an electric field that cancels the magnetic force.

PREREQUISITES
  • Understanding of vector cross products in physics
  • Familiarity with electromagnetic theory, particularly Lorentz force law
  • Knowledge of the right-hand rule for vector direction determination
  • Basic concepts of electric and magnetic fields
NEXT STEPS
  • Study the Lorentz force law in detail, focusing on F = q(E + v × B)
  • Learn about electromagnetic waves and their properties
  • Explore vector calculus applications in physics, particularly cross products
  • Review the right-hand rule and its applications in electromagnetism
USEFUL FOR

Physics students, educators, and professionals in electrical engineering or applied physics who are seeking to deepen their understanding of electromagnetic interactions and vector analysis.

beanus
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So E=vB and {E}={v}cross{B} but if I have for instance v=5j and B=-1k, then E is in the positive i direction. Shouldn't it be in the negative direction? Thanks.
 
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Unless, I'm missing something, it's not true that E = v cross B.

It's F = qv cross B if there is no electric field or F = q(E + v cross B) if there is an electric field.

Unless you want to say that there is an electric field there that is exactly canceling the magnetic force. Then F = 0, and you get E = -v cross B. But that's a very specific situation.
 
beanus said:
So E=vB and {E}={v}cross{B} but if I have for instance v=5j and B=-1k, then E is in the positive i direction. Shouldn't it be in the negative direction? Thanks.
Are you talking about an electromagnetic wave?
If this is the case, I think it is {E}=-{v}cross{B}, in the usual notations.
 
Yes, F=qvXb or F=qvbsin(thata). Try using the right hand rule.

1.) point hand in the direction of v
2.) curl fingers in the direction of B
3.) thumb points in the direction of the force
 
rocketnukem said:
Yes, F=qvXb or F=qvbsin(thata). Try using the right hand rule.

1.) point hand in the direction of v
2.) curl fingers in the direction of B
3.) thumb points in the direction of the force

I don't think this has much to do with the OP.
 

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