A long straight vertical conductor carries a current of 8 A in the upward direction. What is the magnitude of the resultant magnetic induction at a point in the horizontal plane at a distance of 4 cm from the conductor towards south ?

Question

( The horizontal components of earth's magnetic induction $= 4 \times 10^{-5}T$)

$\begin {array} {1 1} (1)\;2\sqrt2 \times 10^{-5}T & \quad (2)\;4\sqrt2 \times 10^{-5}T \\ (3)\;4 \times 10^{-5}T & \quad (4)\;2 \times 10^{-5}T \end {array}$