dl
I
=
∫
µ0
C�
 where I refers to
the current passing through S The sign of I is determined from the
right-hand rule 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