A magnetic field of `5 xx 10^(-5) T` is produced at a perpendicular distance of 0.2 m from a long straight wire carrying electric current. If the permeability of free space is `4 xx 10^(-7)` Tm/A The current passing through the wire in A is

Options

A. 45
B. 40
C. 50
D. 30

Answer

C

Explanation

Given , magnetic field , `B = 5 xx 10^(-5) T`
` r = 0.2 m`
and ` mu_0 = 4pi xx 10^(-7) mT//A`
Magnetic field produced by long straight current (I) carrying wire is given by
`B = (mu_0)/(2pi) . I/r rArr 5 xx 10^(-5) = (4 pi xx 10^(-7) )/(2pi) xx (I)/(0.2)`
` rArr I = (5 xx 10^(-5) xx 2pi xx 0.2)/(4pi xx 10^(-7) ) = 0.5 xx 10^2 = 50 A`