Question

The question Statement $I$ (Assertion) and Statement $II$ (Reason). The question has $4$ choices (a), (b), (c) and (d) out of which ONLY ONE is correct. So, select the correct choice.

Statement $I$: A charged particle is moving in a purely magnetic field with non-zero constant velocity,

Statement $II$: If the direction of motion of charge particle coincides with field direction, then the magnetic force experienced by the charged particle would be zero.

• A. Statement $I$ is True, Statement $II$ is True; Statement $II$ is a correct explanation for Statement $I$
• B. Statement $I$ is True, Statement $II$ is True; Statement $II$ is NOT a correct explanation for Statement $I$
• C. Statement $I$ is True, Statement $II$ is False
• D. Statement $I$ is False, Statement $II$ is True

Answer 1

The correct option is A

Statement $I$ is True, Statement $II$ is True; Statement $II$ is a correct explanation for Statement $I$

Explanation for Assertion statement:

1. The magnetic force on a charged particle is perpendicular to both velocity $\overrightarrow{v}$ and magnetic field$\overrightarrow{B}$, and can never be in the direction of the velocity of the charged particle.
2. The charged particle can move with non-zero constant velocity.

Explanation for Reason statement:

1. The motion of the particle will coincide with the field direction, and then the magnetic force will be zero.
2. Since the velocity is non-zero constant.

Statement $I$ is True, Statement $II$ is True; Statement $II$ is a correct explanation for Statement $I$.

Hence, option (a) is correct.