A long straight wire in the horizontal plane carries as curret of 75 A in north to south direction, magnitude and direction of field B at a point 3 m east of the wire is

Options

A. `4xx10^(-6)T`, vertical up
B. `5xx10^(-6)T`, vertical down
C. `5xx10^(-6)T`, vertical up
D. `4xx10^(-6)T`, vertical down

Answer

C

Explanation

From ampere circuital law
`ointoverline(B).overline(dl)=mu_(0)l_(enc)`
`Bxx2piR=mu_(0)l_(enc)`
or, `B=(mu_(0)l_(enc))/(2piR)=2xx10^(-7)xx(75)/(3)`
or, `=5xx10^(-6)T`
The direction of field at the given point will be vertical up determined by the screw rule or right hand rule.