State Fleming's left-hand rule. Name the physical quantities represented by the thumb and the two fingers used in this rule.
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
Fleming's Left-Hand Rule: Stretch the thumb, forefinger, and middle finger of the left hand mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field and the middle finger points in the direction of the current, then the thumb points in the direction of the force (motion) acting on the current-carrying conductor.
Physical quantities represented:
- Thumb → Direction of force (motion) on the conductor
- Forefinger → Direction of magnetic field (B)
- Middle finger → Direction of current (I)
Source: Chapter 12, Magnetic Effects of Electric Current
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Explanation
- The examiner expects the rule stated in one clear sentence describing the mutual perpendicular arrangement of the three fingers, followed by what each finger represents.
- The three quantities (force, field, current) are the key scorers — one mark each or collectively 2 marks with 1 for the statement.
- Avoid confusing left-hand rule (motor effect / force on conductor) with the right-hand thumb rule (direction of magnetic field around a wire). Fleming's left-hand rule is always about the force experienced by a conductor.
- The words "mutually perpendicular" are important and should appear in your answer.