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

Options

A. Straight line along the x-direction
B. A circle in the `xz-` plnae
C. A circle in the `yz-` plnae
D. A circle in the `xy-` plnae

Answer

B

Explanation

`vec(F) = -e(vec(v) xx vec(B)) implies vec(F) = -e[v hat(i) xxB hat(j)] = evB[-hat(k)]`
That is, force on electron is acting towards negative z-axis. Hence particle will move on a circle in `xz`- plane