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