Assertion(A): A charged particle is moving in a circular path under the action of auniformmagnetic field. During the motion, kinetic energy of the charged particle isconstant.Reason (R): During the motion, magnetic force acting on the particle is perpendiculartoinstantaneous velocity

Step 1: Read the assertion and reason given in the question.

Step 2: Understand the assertion and reason.

Assertion (A): A charged particle is moving in a circular path under the action of a uniform magnetic field. During the motion, kinetic energy of the charged particle is constant.

Reason (R): During the motion, magnetic force acting on the particle is perpendicular to instantaneous velocity.

Step 3: Analyze the assertion and reason.

The assertion states that when a charged particle moves in a circular path under the influence of a uniform magnetic field, its kinetic energy remains constant.

The reason given is that the magnetic force acting on the particle is perpendicular to its instantaneous velocity.

Step 4: Evaluate the assertion and reason.

In this case, the reason supports the assertion. When a charged particle moves in a circular path under the influence of a uniform magnetic field, the magnetic force acting on the particle is indeed perpendicular to its instantaneous velocity. This means that the magnetic force does not do any work on the particle, and therefore, the kinetic energy of the particle remains constant.

Step 5: Provide the final answer.

The assertion is true, and the reason is a correct explanation for the assertion.