Question

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 (35-E12). Using Ampere'* law over the path PQRS, show that such a field is not possible.

Answer 1

We know,

Theoritically B = 0 a t A

If, a current is passed through the loop PQRS, then

B = μ0i/2(l + b) will exist in its vicinity.

Now, As the vector B at A is zero. So there’ll be no interaction

However practically this is not true. As a current carrying loop, irrespective of its near about position is always affected by an existing magnetic field.