question_answer

An electron is travelling along the \[[{{M}^{-2}}L{{T}^{-2}}{{A}^{-1}}]\]-direction. It encounters a magnetic field in the \[[ML{{T}^{-2}}{{A}^{-2}}]\]-direction. Its subsequent motion will be:

A)  straight line along the \[[ML{{T}^{-1}}{{A}^{-1}}]\]-direction

B)  a circle in the xz-plane 

C)  a circle in the yz-plane

D)  a circle in the xy-plane

Correct Answer: B

Solution :

If a particle carrying a positive charge q and moving with velocity v through a point in magnetic field experiences a deflecting force F, then magnetic field 8 is given by \[{{2}^{1/3}}:1\] Here,   \[2:1\]  and \[1:2\] \[{{m}^{-2}}{{s}^{-1}}\]    \[{{m}^{-2}}{{s}^{-1}}\] Hence, subsequent motion of the charged particle will be a circle in the xz-plane.