A beam of electrons starts to accelerate from rest due to a uniform electric field in vacuum, the moving electrons:

Options

A. initially experience a force of mtual repulsion
B. experience a force of mutual attraction after travelling a certain distance
C. will continue to diverge due to electrostatic repulsion
D. will follow parallel lines because there is no force of attraction between them.

Answer

A, B

Explanation

The beam of electrons consists of number of electrons. In moving beam of electrons two types of forces play their part. (i) Electrostatic respulsion due to like charges on electrons and (ii) Magnetic attraction, as the two moving electrons in the same direction behave as two parallel linear conductors carrying current in the same directions. Initially electrostatic repulsion is more effective than the magnetic attraction as speed of electrons is small. When speed of electrons become high, the magnetic attraction becomes more prominent than electrostatic repulsion.