Question

find the ratio between the magnetic fields at point P to that at point Q shown in the diagram​

Answer 1

Answer:

We can assume the given arrangement is of a uniform straight current-carrying wire. Here Q is an inside point and P is an outside point.

Let us take B at P as B₁ and B at Q as B₂.

Now for a uniform straight current- carrying wire,

B ( inside ) ∝ r

B ( outside ) ∝ 1/r

Therefore, B₁/ B₂= 1/r ÷ r= 1/ r²= 4/ a²