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

Options

A. Straight line along the x-diretion
B. A circle in the xz plane
C. A circle in the yz plane
D. A circle in the xy plane

Answer

B

Explanation

We known that the force on a charged particle e due to a magnetic field is given by
`vecF=e(vecvxxvecB)`
Hence `vecv = v_x = hati " and " vecB = B_y hat j`
`therefore vec F = ev_xB_y(hati xx hatj)=ev_(x) B_(y) hatk`
Therefore the subsequent motion of the charged particles will be a circle in the xz plane.