A current of 1 ampere is passed through a straight wire of length 2.0 metres. The magnetic field at a point in air at a distance of 3 metres from either end of wire and lying on the axis of wire will be [MP PET 1995]

• A.   \[\frac{{{\mu }_{0}}}{2\pi }\]
• B.   \[\frac{{{\mu }_{0}}}{4\pi }\]
• C.   \[\frac{{{\mu }_{0}}}{8\pi }\]
• D.   Zero