Question

Figure $A$ and $B$ shown two long straight wires of circular cross-section (a and b with a<b). carryingcurrent $I$which is uniformly distributed across the cross-section. The magnitude of magnetic field $B$ varies with radius $r$ ad can be represented as:

• A.
• B.
• C.
• D.

Answer 1

The correct option is C

The $\left(B\text{vs}r\right)$ graph for wire of radius $R$ is given as

As $a<b$
$\Rightarrow B_a>B_b$, which is given as
$B_a=\frac{{\mu }_{0}i}{2\pi a}$
$B_b=\frac{{\mu }_{0}i}{2\pi b}$
The graph will be