Why Doesn’t a Charge Move in the Direction of the Force in a Magnetic Field?

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Discussion Overview

The discussion revolves around the behavior of a charged particle moving in a magnetic field, specifically addressing why the charge does not move in the direction of the magnetic force acting on it. The scope includes conceptual clarification and technical explanations related to the principles of electromagnetism.

Discussion Character

  • Conceptual clarification, Technical explanation, Debate/contested

Main Points Raised

  • One participant questions why a charge does not move in the direction of the magnetic force when it is perpendicular to its velocity.
  • Another participant argues that the charge does move but clarifies that it does not move 'through' the force since the force is always at a right angle to the motion, resulting in a change in direction but not speed.
  • A third participant introduces Newton's second law, explaining that while the acceleration is in the direction of the force, in circular motion, the acceleration is centripetal, leading to perpendicular motion relative to the force.
  • A later reply references the vector relationship of the magnetic force (F = qV x B) and mentions the right-hand rule to describe the direction of the force.

Areas of Agreement / Disagreement

Participants express differing views on the nature of the charge's movement in relation to the magnetic force. While some agree that the force is perpendicular and leads to a change in direction, there is no consensus on the interpretation of the charge's movement relative to the force.

Contextual Notes

Participants reference Newton's laws and the work-energy theorem, but the discussion does not resolve the underlying assumptions about the motion of charges in magnetic fields or the implications of the right-hand rule.

nikhilthunder
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when a charge moves in magnetic field a force perpendicular to velocity and B acts on charge then why the charge do not move in the direction of that force
 
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it does. where did you get the idea that it doesnt?

well in one sense it doesn't move 'through' the force because the force is always at a right angle to the motion of the particle. so the particles direction changes but its speed doesn't change.
 
Welcome to PF!

nikhilthunder said:
when a charge moves in magnetic field a force perpendicular to velocity and B acts on charge then why the charge do not move in the direction of that force

Hi nikhilthunder! Welcome to PF! :smile:

("why does the charge not move in the direction of that force" :wink:)

From Newton's second law, force = mass times acceleration …

so the acceleration is always in the direction of the force …

but in circular motion, the acceleration is centripetal (towards the centre of the circle), so the charge carries on moving perpendicular to the force. :smile:

(and, as granpa says, the speed doesn't change … so the energy doesn't change … this is because of the work-energy theorem … work done = change in energy, and work done is zero because the force is perpendicular to the motion :wink:)
 
Nik...
There is a Force (vector) F= qV x B (where V and B are vectors) I seem to remember that from many years ago...anyway, the force IS "sideways" via the right hand rule.

Is that the relationship you are questioning?
 

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