Changing resistance
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👩 Teacher’s Guide
🎯 Objective
Students will be able to:
- Explain the key principles of changing resistance
- Use circuit rules and equations correctly
- Apply electrical concepts to real sensor and household circuits
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📝 Teaching Notes
- Key idea to emphasize: Resistance depends on material, length, thickness, and temperature. Higher resistance reduces current for a given voltage.
- Common misconception: Current is “used up” as it passes through components.
- Suggested teaching approach:
- Use clear circuit diagrams and symbols
- Practice Ohm’s law and power calculations
- Include practical work with series and parallel circuits
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💬 Discussion Starter
Ask students:
- Why must a circuit be a complete loop?
- How do series and parallel circuits behave differently?
- Why are sensors useful in everyday electronics?
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🧒 Student Worksheet
Concept and Helping Material
Resistance depends on material, length, thickness, and temperature. Higher resistance reduces current for a given voltage.
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Vocabulary and Definitions
- — Flow of charge, measured in amperes (A)
- — Potential difference that drives current, measured in volts (V)
- — Opposition to current flow, measured in ohms (Ω)
- — V = I × R relationship
- — Rate of energy transfer, P = V × I
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Hands-On Experiment or Activities
Activity 1: Series vs Parallel Lamps
What You Need: cells, bulbs, wires, switch.
What You Do: Build series and parallel circuits and compare brightness.
Think and Talk: What changed?
What stayed the same?
Activity 2: Investigating Resistance
What You Need: wires of different lengths, ammeter, voltmeter.
What You Do: Measure current and voltage, then calculate resistance.
Think and Talk: What changed?
What stayed the same?
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Practice Questions (QA)
1. What is electric current?
2. What is Ohm’s law?
3. How do you measure current?
4. How do you measure voltage?
5. What happens to current in a series circuit?
6. What happens to voltage in a parallel circuit?
7. What is electrical power?
8. How do you calculate electrical energy?
9. What does an LDR do?
10. What does a thermistor do?
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Reflection
- Where are electrical circuits used in daily life?
- Why are sensors important?