An electron is travelling along the x-direction. It encounters a magnetic field in the y-direction. Its subsequent motion wil be

Options

A. straight line along X-direction
B. a circle in the X-Z plane
C. a circle in the YZ plane
D. a circle in the XY plane

Explanation

Here, `vecv=vhati` and `vecB=Bhatj`, `q=-e`
As we know `vecF=q(vecvxxvecB)`
so `vecF=-e(vechatixxBhatj)`
`vecF=-evBhatk` [As `hatixxhatj=hatk`]
So the force will be along-Z-direction, as a result of which the motion of an electron will be a circle in XZ plane.