Magnetic fields and force on a conductor

Repair the common break

Common misconception: Magnetic field direction is the direction a positive charge moves.

Correct model: Construct field patterns from currents and use F = BIℓ sinθ with Fleming’s left-hand rule; define flux density using the perpendicular force case.

Worked transfer

For a straight conductor perpendicular to B, F = BIℓ. Fleming’s left-hand rule gives the force direction; the magnetic-field direction is defined independently using a north pole or current convention.

Guided practice

Explain why “Magnetic field direction is the direction a positive charge moves.” fails. Then construct one example that correctly applies magnetic fields and force on a conductor.

Independent practice

A 0.15 m wire carries 3.0 A perpendicular to a 0.40 T field. Find the force and determine its direction for current east and field north.

Return to the recorded repair plan when the explanation and application are secure enough to re-test.