If as long cylindrical coductor carreis a steady current parallel to its length, then

Options

A. the electric field along the axis is zero
B. the magnetic field along the axis is zero
C. the magnetic field outside the conductor is zero
D. the elctric field outside the conductor is zero

Answer

B, D

Explanation

If current flows in a coductor, then
`E!=o` (for inside points)
`E=0` (for outside points)
`B=mu_0/(2pi)i/R^2` (for inside points)
`B=0` at `r=0,` i.e. at centre
`B=mu_0/(2pi)i/r` for outside points.