Figure shows a cylindrical conductor of inner radius `a` & outer radius `b` which carries a current `i` unifromly spread over its cross section.Show that the magnetic field `B` for points inside the body of the conductor (i.e. `a lt r lt b`) is given by. `B=(mu_(0)i)/(2pi(b^(2)-a^(2)))(r^(2)-a^(2))/r`.Check this formula for the limiting case of `a=0`.

Answer

`(mu_0 i r)/(2 pib^(2))`