Question

An electron enters a region where magnetic field (B) and electric field (E) are mutually perpendicular, then

• A. it will always move in the direction of B
• B. it will always move in the direction of E
• C. it always possesses circular motion
• D. it can go undeflected also

Answer 1

The correct option is D it can go undeflected also

If the magnetic force balances the electric force then electron can go undeflected.
$q\overrightarrow{E}=q(\overrightarrow{v}\times \overrightarrow{B})$
However it can never always move in direction of B since magnetic force acts perpendicular to the motion.
Since there is magnetic field also present therefore, it will not only move in the direction of E.
Due to presence of E circular motion cannot occur.