Question

The magnetic induction at a point P which is distant 4 cm from a long current carrying wire is ${10}^{-3}$ Telsa.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

Answer 1

The correct option is A

$3.33\times {10}^{-9}$ Tesla

$B=\frac{{\mu }_0}{4\pi }.\frac{2i}{r}\Rightarrow \frac{B_1}{B_2}=\frac{r_2}{r_1}\Rightarrow \frac{{10}^{-3}}{B_2}=\frac{12}{4}\Rightarrow B_2=3.33\times {10}^{-9}$ Tesla