Sometimes we show an idealised magnetic field which is uniform in a given region and falls to zero abruptly. One such field is represented in figure . Using Ampere's law over the path PQRS, show that such a field is not possible.

Explanation

We know `int B dl = mu_oi`
Theoretically , at any point a inside
B = 0
If current passes through the loop PQRS
Then =0
As B at A is zero, so there will be no
interaction, but pracitcally this is not ture.
Thus, such a field is not possibal.