Wasted energy
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👩 Teacher’s Guide
🎯 Objective
Students will be able to:
- Explain the main principles of wasted energy
- Describe how electricity is used safely in homes and industry
- Apply energy and power ideas to real appliances and transmission
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📝 Teaching Notes
- Key idea to emphasize: Wasted energy is transferred into unwanted forms, usually heat or sound. Improving efficiency reduces wasted energy.
- Common misconception: The earth wire carries current all the time (it only carries current during a fault).
- Suggested teaching approach:
- Use plug wiring diagrams and safety case studies
- Discuss energy bills and appliance power ratings
- Link transformers to efficient power transmission
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💬 Discussion Starter
Ask students:
- Why is mains electricity AC instead of DC?
- How do safety devices prevent fires and shocks?
- Why is electricity transmitted at very high voltages?
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🧒 Student Worksheet
Concept and Helping Material
Wasted energy is transferred into unwanted forms, usually heat or sound. Improving efficiency reduces wasted energy.
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Vocabulary and Definitions
- — Current flowing in one direction only
- — Current that changes direction repeatedly
- — Safety device that melts to break a circuit if current is too high
- — Switch that automatically breaks the circuit if current is too high
- — Device that changes voltage in AC power systems
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Hands-On Experiment or Activities
Activity 1: Appliance Power Investigation
What You Need: appliance labels, calculator.
What You Do: Compare power ratings and estimate energy use over time.
Think and Talk: What changed?
What stayed the same?
Activity 2: Safety Plug Diagram Study
What You Need: plug diagram, colored pencils.
What You Do: Label live, neutral, and earth wires and explain their roles.
Think and Talk: What changed?
What stayed the same?
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Practice Questions (QA)
1. What is the difference between AC and DC?
2. Why are appliances wired in parallel?
3. What does a fuse do?
4. What is the purpose of the earth wire?
5. What unit is household energy measured in?
6. What is wasted energy usually transferred into?
7. Why transmit electricity at high voltage?
8. What does a transformer do?
9. Give one way to reduce energy use at home.
10. Why are circuit breakers important?
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Reflection
- How can understanding electricity improve safety?
- Why is reducing wasted energy important?