# A long solenoid has 500 turns. When a current of 2 ampere is passed through it, the resulting magnetic flux linked with each turn of the solenoid is $4 \times 10^{-3}\: \omega b$. The self - inductance of the solenoid is :

$\begin {array} {1 1} (1)\;4.0 \: henry & \quad (2)\;2.5 \: henry \\ (3)\;2.0 \: henry & \quad (4)\;1.0 \: henry \end {array}$