Solved: PHYSICS Question for NEET

NEET PHYSICSEasy

A strong magnetic field is applied along the direction of the velocity of an electron. The electron would move along:

a parabolic path

the original path

a helical path

a circular path

Identify Formula: The magnetic force ( $\mathbf{F}$ ) experienced by a charged particle moving with velocity $\mathbf{v}$ in a magnetic field $\mathbf{B}$ is given by the Lorentz force formula: $\mathbf{F} = q(\mathbf{v} \times \mathbf{B})$ The magnitude of this force is $F = qvB \sin\theta$ , where $\theta$ is the angle between the velocity vector and the magnetic field vector.
Analyze Conditions: The problem states that the magnetic field is applied along the direction of the velocity. This implies that the angle $\theta$ between $\mathbf{v}$ and $\mathbf{B}$ is $0^\circ$ (parallel) or $180^\circ$ (anti-parallel).
Calculate Force: Since $\sin(0^\circ) = 0$ and $\sin(180^\circ) = 0$ , the magnetic force on the electron is zero: $F = qvB(0) = 0$
Conclusion: Since no magnetic force acts on the electron, its state of motion remains unchanged (Newton's First Law). Therefore, it continues to move along its original path (straight line) with constant velocity.

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