# Instructor guide: Faraday induction polarity map

Course: Electricity, magnetism, and Maxwell's picture

Suggested time: 45–55 minutes

## Learning target

Learners connect induced-emf magnitude to flux-change rate and polarity to opposition of the change.

## Prepare

- Review flux as field through area.
- Choose a sign convention and display it throughout.
- Prepare one apparent energy-creation claim for critique.

## Facilitation moves

- Ask what changed in the flux, not merely whether a magnet moved.
- Separate polarity from magnitude.
- Trace mechanical input through induced current to dissipation.

## Misconception checks

- **A stronger magnet always means current without input.** Current requires changing flux and a closed circuit; the driver supplies energy against the induced response.
- **Negative voltage means energy was destroyed.** The sign records orientation relative to the declared convention.

## Accessibility and participation

- Describe polarity with words and arrows, not red/blue alone.
- Provide a tactile coil-and-arrow sketch.
- Keep motion optional; static parameter states carry the full lesson.

## Evidence of learning

- A controlled rate comparison
- A correct polarity reversal
- A complete input-to-output energy explanation

## Extension

Add coil resistance and compare open-circuit emf with delivered electrical power.

## Evidence boundary

Assess the learner's reasoning only within the declared model and recorded observations. Do not upgrade a simulation result into a claim about an unmodeled physical system.