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

Options

A. `3.33xx10^(-4)T`
B. `1xx11xx10^(-4)T`
C. `3xx10^(-3)T`
D. `9xx10^(-3)T`

Answer

A

Explanation

`B = (mu_0I)/(2pir)implies B prop 1/r`
As the distance is increased to three time, the magnetic induction reduces to one third . Hence ,
`B = 1/3 xx10^(-13) ` tesla `= 3.33xx10^(-4)` tesla