Question

Uniform electric and magnetic fields are produced in the same direction. An electron moves in such a way that its velocity remains in the direction of electric filed. The electron will

• A. turn towards left
• B. turn towards right
• C. get decelerated
• D. get accelerated

Answer 1

The correct option is C get decelerated

The force due to the magnetic field,

${\overrightarrow{F}}_m=q(\overrightarrow{v}\times \overrightarrow{B})$

$F_m=qvBsin\theta$

The angle between the velocity of the electron and the magnetic field is zero.

$\theta =0^0$

$F_m=qvBsin0=0$

The force due to the electric field,

${\overrightarrow{F}}_e=q\overrightarrow{E}$

${\overrightarrow{F}}_e=-e\overrightarrow{E}$

The electron is a negatively charged particle, the force due electric field is in opposite direction to the electric field. So, the electron gets decelerate.

The correct option is C.