Question

The magnetic induction at apoint P which is at the distance 4 cm from a long current carrying wire is `10^(-3) T`. The field of induction at a distance 12 cm from the current will be
A. `3.33xx10^(-9)`tesla
B. `1.11xx10^(-4)` tesla
C. `3xx10^(-3)` tesla
D. `9xx10^(-2)` tesla

Answer 1

Correct Answer - A
The magnetic field
`beta =(mu_(0))/(2pi)-(2i)/(r ) therefore (beta_(1))/(beta_(2))=(r_(2))/(r_(1))`
`(10^(-8))/(beta_(2))=12/14 rarrbeta_(2)=3.33 xx10^(-4) T`