Question

A charged particle is released from rest in a region of steady and uniform electric and magnetic fields where E$||$B. The particle will follow.

• A. Circular path
• B. Elliptical path
• C. Helical path
• D. Straight line path

Answer 1

Answer: (D)

Straight line path

The force due to electric field is given by
$F_e=qE$
The force due to magnetic field is given by
$F_m=v\times B$
Hence, v and B are in the same direction.
So, $\theta =0^o$
$|F_m|=vB\sin 0^o=0$
Hence, there is no effect of magnetic field on the moving charge particle. So, the charge will move due to electrostatic force only and it follows straight line path.