3 Consider a bar magnet of size l and magnetic moment m, at a distance
r from its mid-point, where r >>l, the magnetic field B due to this bar
is,
0
3
2
r
=µ
π
m
B
    (along axis)
   =
0
3
– 4
r
µ
π
m     (along equator)
4 Gauss’s law for magnetism states that the net magnetic flux through
any closed surface is zero
0
�
�
�
�
�
�
S
B
iS
B
all area
elements
5 Consider a material placed in an external magnetic field B0