A particle of charge ‘q’ and mass ‘m’ starts moving from the origin under the action of an electric field and with a velocity . The speed of the particle will becomes after a time.
is parallel to and is perpendicular to both, therefore path of the particle is a helix with increasing pitch .
Speed of particle at any time ‘t’ is given by
here, at all times because the yz components will remain same.
Only the x component will increase due to electric field.
After some time, it is given that
.