| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Recall and use the equation for 100% efficiency in a transformer I_p V_p = I_s V_s where p and s refer to primary and secondary |
Learning Objective/s:
- Recall the ideal‑transformer power equation IₚVₚ = IₛVₛ.
- Explain how the turns ratio links voltage and current in an ideal transformer.
- Apply the power equation to find an unknown voltage or current when two other quantities are known.
- Analyse transformer problems using both turns‑ratio and power relationships.
- Identify common errors when applying transformer equations.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint slides with transformer diagram
- Worksheet containing practice problems
- Calculator for each student
- Ruler/graph paper for sketching coils (optional)
- Answer key for teacher
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Introduction:
Begin with a quick demonstration: connect a small step‑down transformer to a lamp and ask students what determines the lamp’s brightness. Review that transformers transfer energy via magnetic induction and that, for IGCSE, we treat them as ideal (100 % efficient). Explain that today’s success criteria are to recall the power equation, link it to turns ratio, and correctly solve transformer problems.
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Lesson Structure:
- Do‑now (5'): Students answer a short recall question on the transformer definition and write the equation IₚVₚ = IₛVₛ. Teacher checks responses.
- Mini‑lecture (10'): Explain principle of operation, core, primary/secondary, and derive the power equation and turns‑ratio relationships using slides.
- Guided example (12'): Work through the step‑down example (500 turns primary, 100 turns secondary) together, highlighting each calculation step.
- Pair practice (15'): Students complete two worksheet questions, using turns ratio then the power equation; teacher circulates to provide prompts.
- Common mistakes discussion (5'): Review typical errors (confusing p/s, applying equation when losses matter) and have students correct a flawed solution.
- Quick check (3'): Exit ticket – write the unknown secondary current for a given primary voltage/current and turns ratio.
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Conclusion:
Summarise that in an ideal transformer input power equals output power, so IₚVₚ = IₛVₛ, and that the turns ratio links voltages and currents. Students demonstrated this by solving a step‑down problem and peer‑checking practice questions. For homework, assign three additional transformer problems from the textbook to reinforce the calculations.
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