Which of the following statements is INCORRECT?

The correct answer is Option (3) → A charge moving parallel or antiparallel to the direction of the magnetic field experiences a magnetic Lorentz force.

The magnetic force on a moving charge is \( \vec{F} = q\,\vec{v}\times\vec{B} \), of magnitude \( qvB\sin\theta \).

Option (1) A moving charge produces a magnetic field which in turn exerts a force on another moving charge. — A true statement. A moving charge sets up a magnetic field, and this field acts on another moving charge.

Option (2) An electric charge always experiences a force in an electric field, whether the charge is stationary or in motion. — A true statement. The electric force \( q\vec{E} \) acts on a charge whether it is at rest or moving.

Option (3) A charge moving parallel or antiparallel to the direction of the magnetic field experiences a magnetic Lorentz force. — The incorrect statement. For motion parallel or antiparallel to \( \vec{B} \), \( \theta = 0^\circ \) or \( 180^\circ \), so \( \sin\theta = 0 \) and the Lorentz force is zero.

Option (4) A stationary charge does not produce any magnetic field to interact with an external magnetic field. — A true statement. A magnetic field is produced only by moving charges (currents), so a stationary charge produces none.

NCERT (2026-27):
Magnetic Field, Lorentz Force – “… (ii) The magnetic force \( q\,[\,\mathbf{v}\times\mathbf{B}\,] \) 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.”