Magnetic Dipole
Magnetic dipole is an arrangement of two unlike magnetic poles of equal pole strength separated by a very small distance, e. g., a small bar magnet, a magnetic needle, a current carrying loop etc.
Magnetic Dipole Moment
The product of the distance( 2 l) between the two poles and the pole strength of either pole is called magnetic dipole moment.
Magnetic dipole moment M = m( 2 l) Its SI unit is‘ joule / tesla’ or‘ ampere-metre 2‘. Its direction is from south pole towards north pole. Magnetic Field Due to a Magnetic Dipole( 1) On Axial Line
If r > > l, then B = μ o / 4 π 2M / r 3( ii) On Equatorial Line
B = μ o / 4 π M /( r 2 + l 2) 3 / 2