Question

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

• A.
• B.
• C.
• D.

Answer 1

Answer: (C)

Graph for wire of radius $R$ :

As $b>a$
$B_a>B_b$
$B_a=\frac{{\mu }_{0}i}{2\pi a}$
$B_b=\frac{{\mu }_{0}i}{2\pi b}$