A length L of wire carries a steady current 1. It is bent first to form a coil of 1 turn. The same length is now bent more sharply to give a double loop of smaller radius. The magnetic field at the centre caused by the same current is.................
Options:
(a) A quater of its first value
(b) Un changed
(c) Four times of its first value
(d) A half of its first value