Confused about electric field/velocity/magnetic field vectors

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Discussion Overview

The discussion revolves around the relationships between electric field (E), velocity (v), and magnetic field (B) vectors, particularly in the context of the equation E = v × B. Participants explore the implications of these relationships and the conditions under which they hold true, with references to specific vector values and the right-hand rule.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant states that E = vB and E = v × B, providing an example with specific vector values, questioning the direction of E.
  • Another participant challenges the assertion that E = v × B, clarifying that the correct relationship involves the force F = qv × B, and introduces the possibility of an electric field canceling the magnetic force.
  • A third participant reiterates the initial claim about E = v × B but suggests that it may relate to electromagnetic waves, proposing that E = -v × B in that context.
  • Several participants discuss the right-hand rule for determining the direction of the force, emphasizing its relevance to the discussion but noting it may not directly address the original question.

Areas of Agreement / Disagreement

Participants do not reach consensus on the correct interpretation of the relationships between E, v, and B. Multiple competing views are presented, particularly regarding the conditions under which E = v × B is valid.

Contextual Notes

The discussion includes assumptions about the presence of electric fields and the specific conditions under which the equations apply. There are unresolved questions about the implications of the right-hand rule and its relation to the original query.

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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