A coil of one loop is made from a wore of length L and thereafter a coil of two loops is made from same wire, then the ration of magnetic field at the centre of coils will be:

Question

$\begin{array}{1 1} (1)\; 1:4 \\ (2)\; 1:1 \\ (3)\; 1:8 \\ (4)\; 4:1 \end{array}$