A long straight wire carrying current of `30 A` is placed in an external unifrom magnetic field of induction `4xx10^(4) T`. The magnetic field is acting parallel to the direction of current. The maggnetic of the resultant magnetic inuduction in tesla at a point `2.0 cm` away form the wire is

Options

A. `10^(-4)`
B. `3 xx 10^(-4)`
C. `5 xx 10^(-4)`
D. `6 xx 10^(-4)`

Answer

C

Explanation

`B_(1) = 4 xx 10^(-4) T , I = 30 A `
`B_(2) = (mu_(0) I)/(2pi r) = (4pi xx 10^(-7) xx 30)/(2pi xx 10^(-2) xx 2)`
`= 3 xx 10^(-4) T`
`therefore B_("net") = sqrt(B_(1)^(2) + B_(2)^(2)) = 5 xx 10^(-4) T `