(a) State Ampere's circuital law, expressing it in the integral form.
(b) Two long coaxial inlsulated soenoids, `S_(1)` and `S_(2)` of equal lengths are would one over the other as shown in the figure. A steady current ''I'' flows through the inner solenoid `S_(1)` to the other end B, which is connected to the outer solenoid `S_(2)` through which the same current ''I'' flows in the opposite direction so as the come out at end A. If `n_(1)` and `n_(2)` are the number of turns per unit length, find the magnitude and direction of the net magnetic field at a point
(i) inside on the axis and
(ii) outside the combined system.

Answer

`mu_(0) I (n_(1) - n_(2)), 0`