The magnetic field due to a conductor of uniform cross section of radius `a` and carrying a steady current is represented by

Options

A.
B.
C.
D.

Answer

A

Explanation

Magnetic fiedl inside the conductor `B_(in) prop r` and magnetic fied outside the conductor `B_(out) prop (1)/(r)`
(where `r` is the distance of observation point from axis)
`B = (mu_(0))/(2pi) (Ai)/(r^(3)) implies B prop (1)/(r^(3))`
Ailter: The magnetic field at a point outside the straight conductor is given b y `B = (mu_(0) i)/(2pi r)`
The magentic field at a point inside the conductor is
`B = (mu_(0)i xx r)/(2pi a^(2))`
Magnetic feid inside the conductor `B_(out) = prop (1)/(r)`
(where `r` is the distance of observation point from axis)