A charged particle is released from rest in a region of a uniform mag…

The correct answer is Option (1) → straight line

The magnetic force on a moving charge is \( \vec{F} = q\,\vec{v}\times\vec{B} \). It is zero when the velocity is parallel to the field, because \( \sin 0^\circ = 0 \). A charge moving along the field therefore feels no force, its velocity does not change, and it travels in a straight line at constant speed.

Option (1) straight line — Correct. No force acts, so the motion stays straight and uniform.

Option (2) helical — Incorrect. A helix needs a velocity component both along and across the field.

Option (3) circular — Incorrect. A circle needs the velocity to be perpendicular to the field.

Option (4) elliptical — Incorrect. A magnetic field alone never gives an elliptical path.

Note: It seems that there is a mistake in the original NTA paper, which says the particle is “released from rest”. A charge at rest feels no magnetic force and stays at rest, so it has no path. The case meant is a particle moving along the field, for which the path is a straight line (Option 1).

NCERT (2026-27):
Magnetic Field, Lorentz Force – “… (ii) The magnetic force q[v × B] includes a vector product of velocity and magnetic field. The vector product makes the force due to magnetic field vanish (become zero) if velocity and magnetic field are parallel or anti-parallel. … (iii) The magnetic force is zero if charge is not moving (as then |v| = 0). Only a moving charge feels the magnetic force.”