We have discussed a simplified form of this law If B
is directed along the tangent to every point on the perimeter L of a
closed curve and is constant in magnitude along perimeter then,
BL = m0 Ie
where Ie is the net current enclosed by the closed circuit 7 The magnitude of the magnetic field at a distance R from a long,
straight wire carrying a current I is given by:
π
0
2
I
B
R
µ
=
The field lines are circles concentric with the wire