| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Recall and use the equation P = I^2 R to explain why power losses in cables are smaller when the voltage is greater |
Learning Objective/s:
- Recall the relationship P = I²R and its role in cable losses.
- Explain how increasing transmission voltage reduces current and therefore I²R losses.
- Apply the equations to calculate power loss for different transmission voltages.
- Interpret a transformer diagram to describe step‑up and step‑down processes.
- Evaluate the energy‑efficiency benefits of high‑voltage transmission.
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Materials Needed:
- Projector and laptop for presentation
- Whiteboard and markers
- Calculator worksheets
- Printed transformer diagram handout
- Power‑loss calculation worksheet
- Exit‑ticket slips
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Introduction:
Begin with the question “Why do power stations use transformers to send electricity over long distances?” Review students’ prior knowledge of P = VI and I = P/V. State that by the end of the lesson they will be able to explain and calculate how higher voltage reduces cable losses.
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Lesson Structure:
- Do‑now (5'): Solve a short P = VI problem on the board.
- Mini‑lecture (10'): Introduce transformers, review P = I²R and its significance.
- Guided derivation (10'): Show algebraic steps linking higher voltage to lower I²R loss.
- Numerical example (8'): Work through the 10 kW, 10 kV vs 100 kV table together.
- Group activity (12'): Teams calculate losses for a new voltage (e.g., 50 kV) and present findings.
- Check for understanding (5'): Exit‑ticket question – “If transmission voltage is tripled, how does the I²R loss change?”
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Conclusion:
Recap the key points: higher voltage → lower current → dramatically reduced I²R losses, and transformers enable this process. Collect exit tickets to gauge understanding, and assign homework to complete a worksheet calculating losses for three different voltage scenarios.
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