Question

Electrons are emitted by a hot filament and are accelerated by an electric field as shown in fig. The two stops at the left ensure that the electron beam has a uniform cross-section

• A. the speed of the electron is more at B than at A
• B. the electric current is from left to right
• C. the magnitude of the current is larger at B than at A
• D. the current density is more at B than at A

Answer 1

The correct option is A the speed of the electron is more at B than at A

The electric field is always directed towards the motion of positive charge i.e. from positive to negative.

Here, the electrons are moving to the right and hence positive charge can assumed to move towards negative electrons. When the electrons are emitted from the gun they will get attracted towards the field at A and will be more accelerated. Thus their speed will increase due to the acceleration. Further these electrons are attracted due to field at B and hence their speed will increase more than at A.
The current flows from right to left i.e. opposite to the flow o electrons.

Also, the number of electrons from gun is constant. Hence, the current and current density will remains same at A and B.