Question

An electron is an alpha particle having equal velocity pass at right angle to the magnetic field. In this field which of the case is possible:
A. Both the particles describe a circular path.
B. Both the particles move in the straight path.
C. The radius of the path of an alpha particle is greater than that of an electron.
D. The velocity of an electron becomes more than that of an alpha particle.

Answer 1

Here we have to see the first direction of motion of the charge particles and then see the direction of magnetic field and electric field applied.

Complete step by step solution:
In the case of a positive charge, the force on a charged particle due to an electric field is directed parallel to the electric field vector, and in the case of a negative charge, the force is directed antiparallel. It isn't dependent on particle velocity. Since the equal amount of magnetic fields are applied to the particle's velocity of both the particles are same, so the option D is not correct.

By contrast, a charged particle's magnetic force is orthogonal to the magnetic field vector, and depends on the particle's velocity. You can use the right hand rule to determine the direction of the force.

When moving through a magnetic field a charged particle experiences a force. The simplest case is when a charged particle moves to a uniform B-field perpendicularly. If the field is in a vacuum, the dominant factor which determines the motion is the magnetic field. Since magnetic force is perpendicular to the direction of travel, a charged particle in a magnetic field follows a curved path. And the particle did not follow the straight path. So the option B is not correct.

Hence, option A and C are correct.

Note: Force due to electrical as well as magnetic forces will influence the movement of charged particles. The resulting change to the particle trajectory will differ qualitatively between the two forces, however. Below we'll review the two kinds of force quickly and compare and contrast their effects on a charged particle.