what is magnetic moment?

In physics, astronomy, chemistry, and electrical engineering, the term magnetic moment of a system (such as a loop of electric current, a bar magnet, an electron, a molecule, or a planet) usually refers to its magnetic dipole moment, and is a measure of the strength of the system's net magnetic source. Specifically, magnetic dipole moment quantifies the contribution of the system's internal magnetism to the external dipolar magnetic field produced by the system (i.e. the component of the external magnetic field that drops off with distance as the inverse cube).

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Ramesh