The magnetic induction at a point $P$ which is at the distance of 4 cm from a long current carrying

Question

The magnetic induction at a point $P$ which is at the distance of 4 cm from a long current carrying wire is $10^{-3} \mathrm{~T}$. The field of induction at a distance 12 cm from the current will be\

Professor PC Thomas Classes · Answer

(a) : $B \propto 1 / r$, for given current. As the distance is increased to three times, the magnetic induction reduces to one third.\ Hence $B=\frac{1}{3} 	imes 10^{-3} \mathrm{~T}=3.33 	imes 10^{-4} \mathrm{~T}$\