Q. A cylindrical long wire of radius R carries a current I uniformly distributed over the cross-sectional area of the wire. The magnetic field at a distance x from the surface inside the wire is

(a) $\displaystyle \frac{\mu_0 I}{2\pi (R-x)} $

(b) $\displaystyle \frac{\mu_0 I}{2\pi x } $

(c) $ \displaystyle \frac{\mu_0 I}{2\pi (R + x)} $

(d) None of these

Ans : (d)