Q 12-04-139JEE MainJEE Main 2022 (24 Jun, Shift 1)Easy
Given below are two statements: One is labelled as Assertion (A) and the other is labelled as Reason (R).
Assertion (A): In a uniform magnetic field, speed and energy remain the same for a moving charged particle.
Reason (R): A moving charged particle experiences magnetic force perpendicular to its direction of motion.
Answer: (A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.
The magnetic force $q\vec v\times\vec B$ is always perpendicular to the velocity, so it does no work. Hence the kinetic energy, and therefore the speed, stays constant. Both statements are true and (R) explains (A).
Solution by Sreeraj P, M.Sc Physics