Is there any way possible a magnetic field can cancel out an electric field?

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Discussion Overview

The discussion centers around the possibility of a magnetic field canceling out an electric field, particularly in the context of the Lorentz force and its implications for charged particles. Participants explore the relationship between electric and magnetic forces and seek clarification on specific statements related to this interaction.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether a magnetic field can cancel an electric field, referencing the Lorentz force as a framework for understanding this interaction.
  • One participant expresses confusion about a specific statement regarding the direction of the magnetic force needed to cancel the electric force, indicating a need for clarification.
  • Another participant explains that for a negatively charged particle, the electric force acts in the opposite direction to the electric field, suggesting that the magnetic force must align appropriately to achieve cancellation.
  • Participants discuss the conditions under which magnetic forces can counteract electric forces, noting that while complete cancellation in three-dimensional space may not be possible, specific constraints can allow for effective cancellation in certain scenarios.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the question of cancellation, as there are varying interpretations of the conditions under which magnetic and electric forces interact. Some agree that under specific conditions, cancellation can occur, while others remain uncertain about the general applicability of this idea.

Contextual Notes

Limitations include potential misunderstandings of the Lorentz force equation and the directional relationships between electric and magnetic forces, which are not fully resolved in the discussion.

darknight08
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Is there any way possible a magnetic field can cancel out an electric field?

Thanks !
 
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darknight08 said:
Is there any way possible a magnetic field can cancel out an electric field?

Thanks !

Are you familiar with the Lorentz force? What can you tell us about your question?
 
The thought was inspired by the passage and question below. Also, I still don't understand the explanation thoroughly. I understand the electric field portion, but not the magnetic field.

http://imageshack.us/m/847/8320/passage1.jpg
http://imageshack.us/m/197/7190/answerexplanation.jpg

Thanks!
 
More specifically, I don't understand this statement: "The magnetic force, in order to cancel the electric force, must point upward" ??
 
darknight08 said:
More specifically, I don't understand this statement: "The magnetic force, in order to cancel the electric force, must point upward" ??

Because the E field points up, the electric force on the electron is down. Therefore, to cancel the electric force with a magnetic force, the magnetic force has to point up.

And to answer your original question in the context that you've shown, yes, for certain situations you can get a manetic field to cancel the force on a charged particle from an electric field. In the general 3-d case you can't get the fields to "cancel", but when you apply some physical constraints on the situation, you can make the forces cancel.

That's why I asked if you are familiar with the Lorentz Force:

http://en.wikipedia.org/wiki/Lorentz_force

.
 
berkeman said:
Because the E field points up, the electric force on the electron is down. Therefore, to cancel the electric force with a magnetic force, the magnetic force has to point up.

I am still having hard time understanding why if a magnetic force points in the same direction as an Electric field, it will cancel?
 
darknight08 said:
I am still having hard time understanding why if a magnetic force points in the same direction as an Electric field, it will cancel?

The electric force on a *negatively* charged particle is in the opposite direction as the Electric field. Look at the Lorentz Force equation:

F = qE + q(v x B)

If q is negative (like is for electrons), the electric force is opposite the E field direction. Just remember that the E field direction is defined as the direction of force on a *positive* test charge.

Does that help?
 

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