A long straight wire of radius `a` carries a steady current `i`. The current is uniformly distributed across its cross section. The ratio of the magnetis field at `(a)//(2) and (2a)` is

A long straight wire of radius a carries a steady current I. the current is uniformly distributed across it cross-section. The ratio of the magnetic field at a/2 and 2a is

A long straight wire of radius a carries a steady current I. The current is uniformly distributed over its cross section. The ratio of the magntic fields B and B' at radii distance (a)/(2) and 2a respectively, from the axis of the wire is

A long straight wire of radius carries a steady current I. The current is uniformly distributed over its cross - section. The ratio of the magnetic fields B and B', at a radial distances a/2 and 2a respectively, from the axis of the wire is