Circular regiions `(1)` and `(2)` have current densities J and `-J` respectively, such that their region of intersection carries no current. Magnetic field in their region intersection is

Options

A. Uniform, proportaional to `(r_(1)+r_(2))-d`
B. Uniform, proportional to d
C. non- uniform
D. Zero

Answer

B

Explanation

`ointvec(B).d vec(i)=mu_(0)hat(i)_(i n)`
or `" "Bxx2pir=mu_(0)(jxxpir^(2))`
or `" "B=(mu_(0)Jr)/(2)`
If `d_(1)` and `d_(2)` are the distances from the centres of the regions, then
`=(mu_(0)J)/(2)vec(d)`