A very long straight conducting wire, lying along the z-axis, carries a current of 2A. The integral `ointvecB.dvecl` is computed along the straight line PQ, where P has the coordinates `(2cm,2cm,0)` and Q has the coordinates `(2cm, 2cm ,0)`. The integral has the magnitude (in SI units)`

Options

A. `pi/2xx10^-7`
B. `8pixx10^-7`
C. `2pixx10^-7`
D. `pixx10^-7`

Answer

D

Explanation

(a) `int_(PAQ)vecB.dvecl=int_(RBQ)vecB.dvecl ( :'int_(PCR)vecB.dvecl=0)`
`((mu_0I)/(2piR))(pi/4R)`
`=((4pixx10^-7)(2))/16=(pixx10^-7)/2 S.I. units`