Magnetic Effects & Magnetism

JEE Main level, single correct, medium

142 of 276

Question 142 of 276

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.

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Answer: (A) Both Assertion and Reason are true and Reason is the correct explanation of Assertion.

The force experienced by the charge particle is perpendicular to the instantaneous velocity at all instants as F⃗=q(v⃗×B⃗)\vec{F}=q\left(\vec{v}\times \vec{B}\right).
Hence, the magnetic force cannot bring any change in the speed of the charged particle. Since, the speed remains constant, the kinetic energy also remains constant.

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