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

$B\propto r$ for r < a           

$B\propto \frac{1}{r^2}$ for r > a

Magnetic field inside the conductor $B_{in}\propto r$and magnetic field outside the conductor $B_{out}\propto \frac{1}{r}$  

(where r is the distance of observation point from axis)