JEE Main 2022 · 24 Jun · Shift 1 · Physics Q32

PhysicsSingle correct+4 / -1Question 32 of 90

Given below are two statements : One is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A) : In an uniform magnetic field, speed and energy remains the same for a moving charged particle.

Reason (R) : Moving charged particle experiences magnetic force perpendicular to its direction of motion.

Both (A) and (R) are true and (R) is the correct explanation of (A).

Both (A) and (R) are true but (R) is NOT the correct explanation of (A).

(A) is true but (R) is false.

(A) is false but (R) is true.

Answer and worked solution

Official answer: A

Reason. The magnetic force $q\vec v\times\vec B$ is always perpendicular to $\vec v$ , so it does no work.

Assertion. With no work done, kinetic energy and hence speed stay constant. So (R) is true and explains (A).

(A)

Topics:Force on a moving charge Work-energy theorem

JEE Main 2022 · 24 Jun · Shift 1, Physics question 32