| Lesson Plan |
| Grade: 9 |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Define efficiency as: (a) (%) efficiency = (useful energy output) / (total energy input) (× 100%) (b) (%) efficiency = (useful power output) / (total power input) (× 100%) recall and use these equations |
Learning Objective/s:
- Define efficiency using both the energy‑based and power‑based formulas.
- Calculate percentage efficiency for given energy or power values.
- Compare typical efficiencies of various energy resources and explain cost and environmental implications.
- Apply efficiency calculations to real‑world examples such as power plants and household appliances.
- Interpret efficiency results to evaluate system performance and suggest improvements.
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Materials Needed:
- Projector and screen
- Printed worksheet with practice questions and data table
- Calculators (one per pair)
- Whiteboard and markers
- Laptop for slide presentation
- Exit‑ticket slips
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Introduction:
Begin by asking students how much of the electricity they use actually does useful work, using a light‑bulb example to hook interest. Recall that they already know the concepts of energy, power and unit conversions. Explain that today they will learn to quantify that “useful” portion with efficiency formulas and will be able to evaluate real devices and energy sources.
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Lesson Structure:
- Do‑now (5'): Students calculate the efficiency of a 60 W bulb that produces 12 W of light on a mini‑whiteboard; teacher reviews answers.
- Mini‑lecture (10'): Present the two efficiency equations, emphasising the link between energy and power.
- Guided example (8'): Work through the coal‑power‑plant calculation together using the projector.
- Group activity (12'): In pairs, students use the handout to compare typical efficiencies of different resources, fill a comparison chart and discuss reasons for variation.
- Independent practice (10'): Students solve the three practice questions from the notes; then peer‑check answers.
- Quick quiz (5'): Exit‑ticket – one sentence explaining why higher efficiency is desirable.
- Recap (5'): Teacher summarises key points and highlights how the formulas apply across contexts.
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Conclusion:
Review the two formulas and the main take‑aways about waste, cost and environmental impact. Collect exit tickets to gauge understanding and assign a short homework task: students must find the rated efficiency of a household appliance (e.g., a refrigerator) and write a brief comment on its performance.
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