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Q & A: More on magnetic forces

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Most recent answer: 03/24/2009
Q:
The magnetic force for a charged particle is given by the formula F=qv x B.Where B is the magnetic field.My doubt is that will there be no magnetic force on a body if there is no charge in it.And will there be no force on a body if the body is not in motion(means if it doesn't have any velocity).If so why is an iron bar at rest is attracted by a magnet.
- Prudhvi Raj Borra (age 16)
Machilipatnam,Andhra Pradesh,India.
A:
First, read the answer to #14004.   The reason a bar magnet is attracted to a magnetic material such as iron is that the bar magnet induces an accompanying magnetic field in the iron. No velocity is involved.   These two fields interact and as such have an overall energy associated with the total field.  The lowest energy state is when the bar magnet is closest to the iron plate, hence an attraction.

LeeH

Perhaps another important point is that the magnetism in typical materials comes mainly from intrinsic magnetism of the particles (mainly electrons) associated with their 'spin', not from real currents.  Mike W.


(published on 03/24/2009)

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