Magnetic Moment (^) M:
M m 2
Its unit is ampere metre^2.
Magnetic Field
It is also called as magentic flux density (or)
magnetic field vector ( )B.Magnetic induction at a point in a magnetic field is
defined as force experienced by a unit north pole
placed at that point.
B F
m
S.I unit is tesla or weber / m^2
The magnetic field induction due to a pole of pole
strength m at a distance ‘d’ is given by B 0 =
20
4 dm
- Torque on a Magnetic Dipole
In vector notation M B
- Potential energy of a magnetic dipole
(^) U MBcos M B
The work done by an external agent in deflecting a
magnet from angular position 1 to an angular
position 2 with the field is given as
W U U 2 U 1 MB(cos 1 cos ) 2
- Field of a Bar Magnet
(1) Axial line: (^02) 2 2
2
a 4 ( )
Md
B
d l
For a short bar magnet i.e., l d^2 ^2 ;
then Ba
0
3
2
4
M
d
(2) Equatorial line:
0
e 4 ( 2 2 3/ 2)
B M
d l
For a short bar magnet i.e., l d^2 ^2 ; then
Be =
0
4
^
- Magnetic Moment :
- Magnetic Field
- Torque on a Magnetic Dipole
- Potential energy of a magnetic dipole
- Field of a Bar Magnet
3M
d