An aluminium rod is suspended horizontally between the poles of a horseshoe magnet with the magnetic field directed vertically upward. When current is passed through the rod, it deflects to the left. What will happen to the direction of deflection if (i) the direction of current is reversed, and (ii) the poles of the magnet are interchanged (so the field is now directed downward)?
Generated by claude-sonnet-4-6 · 2026-06-26 01:09 · grounding rag
Model Answer
Using Fleming's Left-Hand Rule:
(i) Current reversed: The direction of deflection reverses — the rod now deflects to the right (opposite to the original left deflection), since reversing the current reverses the direction of force.
(ii) Poles interchanged (field now downward): The direction of deflection again reverses — the rod deflects to the right, since reversing the magnetic field direction also reverses the force on the conductor.
Source: Chapter 12, Section 12.3 — Force on a Current-Carrying Conductor in a Magnetic Field
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Explanation
- The examiner expects you to apply Fleming's Left-Hand Rule (or cite the textbook activity) and state the new direction clearly for each case.
- Key principle: force direction reverses if either current OR magnetic field is reversed — both cases give deflection to the right here.
- Don't just say "reverses" — name the direction (right/left) for full marks.
- One mark per correct sub-part.