Safety boundary
Use simulations or supervised low-voltage coil/magnet activities only. Do not use mains electricity, high-current coils, or improvised high-voltage equipment.
Explicit physics instruction
Magnetic fields describe how magnets and moving charges interact. Field lines are a representation of direction and relative strength, not physical strings.
A current-carrying conductor in a magnetic field can experience force whose direction depends on current and field orientation.
Magnetic force on a moving charge is perpendicular to both velocity and field in the ideal model, so it can change direction of motion without doing mechanical work on speed.
Vocabulary: magnetic field; current; magnetic force; moving charge.
Worked example
A positive charge moving perpendicular to a magnetic field experiences a sideways force; reversing charge sign reverses force direction.
Guided question
Why can a magnetic force bend a particle path without changing its speed in the ideal model?
Independent work
- Sketch field patterns for a bar magnet and straight current.
- Predict force direction in three simple diagrams.
- State one limit of field-line drawings.
Misconception check
Magnetic field lines are representations, not material tracks.
Formative check
What motion condition gives zero magnetic force on a moving charge in the simple model?
Reveal response
When velocity is parallel or antiparallel to the field.
Mentor evidence conference
Ask Archaemenes to audit direction rules, rate reasoning, energy source, and model scope.
Teacher guidance
Foundation: Use direction diagrams.
Core: Predict magnetic-force direction qualitatively.
Extended: Analyze circular motion of charges in uniform fields.