Q. At a distance of $10\ cm$ from a long straight wire carrying current, the magnetic field is $0.04\ T$. At the distance of $40\ cm$, the magnetic field will be
A) 0.01 $T$
B) 0.02 $T$
C) 0.08 $T$
D) 0.16 $T$
Explanation
(a) $B \propto \frac{1}{r} \Rightarrow \frac{B_{1}}{B_{2}} = \frac{r_{2}}{r_{1}} \Rightarrow \frac{0.04}{B_{2}} = \frac{40}{10} \Rightarrow B_{2} = 0.01\ T$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.