A circular loop of radius ' \(r\) ' of conducting wire connected with a voltage source of zero internal resistance produces a magnetic field 'B' at its centre. If instead, a circular loop of radius ' \(2 r\) ', made of same material, having the same cross section is connected to the same voltage source, what will be the magnetic field at its centre ?
(A) \(\frac{B}{2}\)
(B) \(\frac{B}{4}\)
(C) \(2 B\)
(D) \(B\)