Question

A long straight wire of radius `a` carries a steady current `i`. The current is uniformly distributed across its cross section. The ratio of the magnetis field at `(a)//(2) and (2a)` is
A. `1//4`
B. 4
C. 1
D. `1//2`

Answer 1

Correct Answer - 3
`B_(1)=(mu_(0))/(2pi)(ir_(1))/(R)B_(2)=(mu_(0))/(2pi)(i)/(r_(2))`