Science (086) — AI-generated practice question

No, I do not agree with the student's claim.

A stationary charged particle has no velocity (v = 0). The magnetic force on a charged particle depends on its motion through the field. If the particle is stationary, it experiences no force, regardless of the strength of the magnetic field.

Condition for force: A charged particle experiences a force in a magnetic field only when it is moving, and the force is maximum when the direction of motion is perpendicular to the magnetic field. If current (motion of charge) and field are mutually perpendicular, Fleming's left-hand rule gives the direction of force.

Source: Section 12.3, Force on a Current-Carrying Conductor in a Magnetic Field, Chapter 12

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• The key concept: magnetic force requires motion of the charge. A stationary charge contributes zero current, so no force acts.
• The textbook states: "the displacement of the rod is largest when the direction of current is at right angles to the direction of the magnetic field" — this implies force depends on current (moving charges) and angle.
• Examiners expect: (1) clear disagreement with the claim, (2) reason (no velocity = no force), (3) the condition (particle must be moving, ideally perpendicular to field). All three earn the 3 marks.