Q. The magnetic induction at a point $P$ which is at a distance 4 $cm$ from a long current carrying wire is $10^{- 8}tesla$. The field of induction at a distance $12\ cm$ from the same current would be
A) $3.33 \times 10^{- 9}tesla$
B) $1.11 \times 10^{- 4}tesla$
C) $3 \times 10^{- 3}tesla$
D) $9 \times 10^{- 2}tesla$
Explanation
(a) $B = \frac{\mu_{0}}{4\pi} \bullet \frac{2i}{r} \Rightarrow \frac{B_{1}}{B_{2}} = \frac{r_{2}}{r_{1}} \Rightarrow \frac{10^{- 8}}{B_{2}} = \frac{12}{4}$
$\Rightarrow B_{2} = 3.33 \times 10^{- 9}tesla$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.