Is there a net force on a magnet in a uniform magnetic field?

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vicente rosillon

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vicente rosillon asked the Naked Scientists:
Is there a net force exerted on a bar magnet in a uniform magnetic field?

What do you think?
« Last Edit: 26/09/2011 12:30:03 by _system »


Offline JP

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Is there a net force on a magnet in a uniform magnetic field?
« Reply #1 on: 26/09/2011 21:03:41 »
Hi Vicente,

If the magnetic field is uniform, then the bar magnet will essentially rotate to align itself with the magnetic field.  There will be a force trying to make that rotation happen.  The magnet won't generally fly along the field with a lot of force, unless the field isn't uniform. 

You can see this principle at work in a compass, for example, where the needle aligns itself with the earth's magnetic field.  It's also used in MRI (magnetic resonance imaging) machines, where electrons in the atoms in your body act like little magnets, and the machine applies a magnetic field to get them all to line up, which allows it to form an image of the different tissues in your body by basically measuring the density of electrons in different tissues.