B Magnetic Dipole Moment of a bar magnet

A bar magnet will have a definite magnetic dipole moment, irrespective of the presence of an external field. Why is the moment, then, always defined in relation to the torque it would feel in an external field? Is there any other definition for the same?
 

jim hardy

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Thank you. But I still can't get it for a bar magnet.
 

jim hardy

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Why is the moment, then, always defined in relation to the torque it would feel in an external field? Is there any other definition for the same?
That is its most readily observable characteristic, its tendency to align with an external field. Think Boy Scout Compass needle....

So why not use that to describe its strength?

According to these guys
https://www.chegg.com/homework-help/definitions/magnetic-dipoles-2
its definition is simpler, and Torque is the result of applying an external field.

upload_2019-1-13_10-24-24.png


as explained in that earlier Hyperphysics link.

upload_2019-1-13_10-28-7.png
 

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