Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: Sketch and interpret graphs of e.m.f. against time for simple a.c. generators and relate the position of the generator coil to the peaks, troughs and zeros of the e.m.f.
Learning Objective/s:
  • Describe how coil orientation influences magnetic flux and the induced emf in a simple AC generator.
  • Sketch a sinusoidal emf‑time graph and correctly label peaks, troughs and zero crossings.
  • Explain the link between coil angle, rotation speed and the amplitude/frequency of the emf.
  • Predict the effect of changing N, B, A or ω on the graph’s amplitude and frequency.
Materials Needed:
  • Projector and screen
  • Whiteboard and markers
  • Printed worksheet with coil‑position table and graph template
  • Simple hand‑cranked AC generator or simulation software
  • Ruler, graph paper and calculator
 Introduction:
Begin with a quick demonstration of a hand‑cranked generator producing a humming sound, then ask students what they expect the voltage to look like over time. Review the concept of magnetic flux and Faraday’s law as prerequisite knowledge. State that by the end of the lesson they will be able to draw and interpret the emf‑time graph and link it to coil positions.
Lesson Structure:
  1. Do‑now (5'): Students complete a short recall quiz on magnetic flux and Faraday’s law.
  2. Mini‑lecture (10'): Explain the principle of operation of a simple AC generator and derive the sinusoidal emf equation.
  3. Interactive demonstration (8'): Show the generator rotating, pause at key angles (0°, 90°, 180°, 270°) and discuss flux and emf values.
  4. Guided practice (12'): Students fill in the provided table linking coil angle, flux, emf and graph points.
  5. Graph sketch activity (10'): Using graph paper, learners draw the emf‑time sine wave, label peaks, troughs and zero crossings, and annotate corresponding coil positions.
  6. Concept check (5'): Quick oral questioning or click‑quiz to verify understanding of how N, B, A and ω affect amplitude and frequency.
  7. Reflection (5'): Students write one sentence summarising the physical meaning of a peak and a zero on the graph.
Conclusion:
Recap the relationship between coil orientation and the sinusoidal emf graph, emphasizing the four key positions. Ask each pupil to write an exit ticket noting one way to increase the emf amplitude. Assign homework: complete a worksheet that asks students to predict graph changes when N, B, A or ω are varied.