An electron is moving along the positive $x$-axis. If uniform magnetic field is applied parallel to the negative $z$-axis, then
A. The electron will experience magnetic force along positive $y$-axis
B. The electron will experience magnetic force along negative $y$-axis
C. The electron will not experience any force in magnetic field
D. The electron will continue to move along the positive $x$-axis
E. The electron will move along circular path in magnetic field
Choose the correct answer from the options given below:
Answer: (C) B and E only
$\vec F=q\vec v\times\vec B=(-e)(v\hat i)\times(-B\hat k)=evB(\hat i\times\hat k)=-evB\hat j$.
The force is along $-y$ and perpendicular to the velocity, so the electron moves in a circle: B and E.
Solution by Sreeraj P, M.Sc Physics