The magnetic induction at a point P which is at a distance of 4 cm from a long current carrying wire is `10^(-8)` T. The induction at a distance 12 cm from same current carrying wire is

Options

A. `3.33 xx 10^(-9)` tesla
B. `1.11 xx 10^(-4)` tesla
C. `3 xx 10^(-3)` tesla
D. `9 xx 10^(-2)` tesla

Answer

A

Explanation

`B = (mu_(0))/(4pi ) . (2i)/( r) implies (B_(1))/(B_(2)) = (r_(2))/(r_(1)) implies (10^(-8))/(B_(2)) = (12)/(4)`
`implies B_(2) = (4)/(12) xx 10^(-8) = 3.33 xx 10^(-9) T`