Question

An electron enters a chamber in which a uniform magnetic field is present as shown.
An electric feild of appropriate magnitude is also applied so that the electron travels undeviated without any change in its speed through the chamber. We are ignoring gravity. Then, the direction of the electric field is

• A. Opposite to the direction of the magnetic field.
• B. Opposite to the direction of the electron's motion.
• C. Normal to the plane of the paper and coming out of the plane of the paper.
• D. Normal to the plane of the paper and into the plane of the paper.

Answer 1

The correct option is D Normal to the plane of the paper and into the plane of the paper.

Direction of magnetic force is $e(V\times B)$ direction is into the paper,charge of electron is negative.

Now electric force on electron will be opposite to the direction of electric field. Hence the Electric field should be normal to plane of paper and into the paper