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A long straight wire along the z-axis ca...

A long straight wire along the z-axis carries a current I in the negative z-direction. The magnetic vector field `vec(B)` at a point having coordinnates (x, y) in the z = 0 plane is

A

`(mu_0I(yhati-xhatj))/(2pi(x^2+y^2))`

B

`(mu_0I(xhati+yhatj))/(2pi(x^2+y^2))`

C

`(mu_0I(xhati-yhatj))/(2pi(x^2+y^2))`

D

`(mu_0I(xhati-yhatj))/(2pi(x^2+y^2))`

Text Solution

Verified by Experts

The correct Answer is:
A
The wire carries a current I in the -ve z-direction.
`vecB` is perpendicular to OP
`vecB =(B sin theta) hati -(B cos theta) hatj`
`sin theta=y/r , cos theta=x/r ,B =(mu_0I)/(2pir)`
`vecB=(mu_0I)/(2pir^2)(yhati-xhati)=(mu_0I(yhati-xhatj))/(2pi(x^2+y^2))`
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