Question

What is the difference between a magnetic dipole and a magnetic moment?

Answer 1

Magnetic dipole

Magnetic dipole is analogous to an electric dipole which can be represented as a system of two magnetic charges. It is the current carrying coil like a bar magnet placed in the magnetic field. In other words, it is generally a tiny magnet of microscopic to subatomic dimensions equivalent to a flow of electric charge around a loop. It is a pair of equal and opposite magnetic poles separated by a small distance.

Magentic moment:

To account for the torque on the current carrying coil due to the magnetic field, we assign a magnetic dipole moment to the coil.

Magnetic moment is a vector quantity that represents magnetic strength. It a measure of the torque it would experience in a one tesla magnetic field. It is expressed as the product of the pole strength and the separation distance between the poles.

The equation for magnetic moment is given as µ = i A whose direction is perpendicular to A (Area) and determined by the right-hand rule. Like a compass needle, the magnetic moment (µ) will seek to align with an externally applied magnetic field. The unit for magnetic moment in terms of SI base units is A. m² where A is the ampere and m is the meter.