A wire in the form of a square of side ?a? carries a current i. Then the magnetic induction at the centre of the square wire is (Magnetic permeability of free space =\[{{\mu }_{o}})\] [EAMCET 2001]

• A.            \[\frac{{{\mu }_{0}}i}{2\pi a}\]        
• B.            \[\frac{{{\mu }_{0}}i\sqrt{2}}{\pi a}\]
• C.            \[\frac{2\sqrt{2}{{\mu }_{o}}i}{\pi a}\]   
• D.            \[\frac{{{\mu }_{0}}i}{\sqrt{2}\pi \,a}\]