Question

if electric field is applied parallel to the direction of electron beam , the electron will (A) speed up (B)slow down (C) deflect (D)not change its state​

Answer 1

Given:

Electric field is applied parallel to the direction of electron beam.

To find:

Direction of displacement of electron beam?

Calculation:

Force on a moving charge (here electron) is given as :

$\boxed{ \bf\vec{F} = q( \vec{v} \times \vec{B})}$

$\sf \implies | \vec{F}| = q \times v\times B \times \sin( \theta)$

• $\theta$ is the angle between Velocity vector and Field Intensity vector.

• Since Velocity vector and B vector is parallel, value of $\theta$ is 0°.

$\sf \implies | \vec{F}| = q \times v\times B \times \sin( {0}^{ \circ} )$

$\sf \implies | \vec{F}| = q \times v\times B \times 0$

$\sf \implies | \vec{F}| = 0$

So, the electron will not get deflected , hence will not change its state (option 4).