Question

A long straight wire of radius $R$ carries a steady current, $I_0$, uniformly distributed throughout the cross-section of the wire. The magnetic field at a radial distance $r$ from the center of the wire, in the region $r > R$, is

• A. $\dfrac{\mu_0 I_0}{2\pi r}$
• B. $\dfrac{\mu_0 I_0}{2\pi R}$
• C. $\dfrac{\mu_0 I_0 R^2}{2\pi r}$
• D. $\dfrac{\mu_0 I_0 r^2}{2\pi R}$
• E. $\dfrac{\mu_0 I_0 r^2}{2\pi R^2}$

Hint:

Outside the wire, treat current as concentrated at the center.

Answer 1

The Correct Option is A