Understanding Resistance in Circuits

Lesson Overview

Subject: Science
Year Group: Year 6
Curriculum Area: Electricity – KS2 Science National Curriculum (England)
Time: 50 minutes
Class Size: 26 students

Learning Question (LQ)

How does the number of components affect resistance, and why?

Success Criteria

• I can describe the relationship between the number of bulbs in a circuit and the bulb brightness.
• I can describe the link between the number of components and the amount of resistance in a circuit.
• I can explain why the number of bulbs in a circuit affects their brightness.

Working Scientifically Objectives

• I can use scientific vocabulary when writing a conclusion.
• I can use scientific knowledge to explain an observation.

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Lesson Structure (50 minutes)

1. Starter – Engaging Question (5 minutes)

Objective: Generate curiosity and assess prior knowledge.

• Begin by holding up a simple series circuit with one bulb and a battery. Turn it on and ask:
  • “What do you think will happen if I add another bulb? Will they stay as bright, dim, or go off?”
• Allow students to make predictions in pairs and share answers with the class.
• Explain that today they will investigate how adding more components affects a circuit’s resistance and bulb brightness.

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2. Explanation & Key Vocabulary (10 minutes)

Objective: Introduce resistance and key scientific concepts.

• Display these key words on the board:

  • Circuit – A complete path for electricity to flow.
  • Component – A part of a circuit (e.g., bulb, battery, wire).
  • Resistance – A force that makes it harder for electricity to flow.
  • Series Circuit – A circuit where components are connected one after another in a single loop.
  • Voltage – The electrical force from a battery that pushes current around the circuit.

• Explain in simple terms:

  • Electricity is like water in pipes – if the pipe (wire) stays the same but we make the path harder (adding components), the flow slows down.
  • More bulbs = more resistance, meaning less energy gets to each bulb, making them dimmer.

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3. Practical Investigation (20 minutes)

Objective: Observe and record how adding bulbs changes brightness.

Materials (per group of 4 students)

• 4 wires with crocodile clips
• 3 bulbs
• 1 battery (cell)
• 1 switch

Instructions

1. Set Up Baseline – Students create a basic circuit with one bulb, battery, and switch. They turn it on and observe the brightness.
2. Increase Components – Gradually add a second and then a third bulb in series, observing each time.
3. Record Observations – Students note changes in brightness at each stage.

Discussion Questions During Investigation

• What do you notice about the brightness as we add more bulbs?
• What do you think is happening inside the circuit to cause this?
• Does anyone have a real-world example where extra components affect performance? (e.g., a torch with low batteries making dimmer light).

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4. Conclusion & Scientific Explanation (10 minutes)

Objective: Link observations to scientific principles.

1. Class Discussion

   • Ask students: Why do you think the bulbs got dimmer?
   • Guide them to understand that more bulbs create more resistance, meaning less energy reaches each one.
   • Link back to the water pipe analogy—more barriers (bulbs) slow the flow (electricity).

2. Writing a Scientific Conclusion (Individual Task)

   • Students write a short paragraph in their books using sentence starters such as:
     • When we added more bulbs, the brightness… because…
     • Resistance increased because…
     • This investigation shows that…
   • Encourage the use of key scientific vocabulary.

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5. Plenary & Real-World Connections (5 minutes)

Objective: Reinforce learning by linking to real-world applications.

• Show an image of a string of Christmas lights and ask: How does this connect to what we learned?
• Explain how some lights are wired in series, and if one fails, the resistance changes the brightness of others.
• Quick-fire recap questions:
  • What happens to resistance when we add more bulbs?
  • Why does this make lights dimmer?
  • How could we make bulbs stay bright with more components? (Introduce the idea of parallel circuits for future lessons.)

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Assessment Opportunities

• Formative: Observing student discussions and predictions during practicals.
• Summative: Written conclusions demonstrating an understanding of resistance.
• Verbal: Responses in plenary questioning.

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Differentiation Strategies

• Support: Provide sentence starters for scientific conclusions. Use visuals to explain concepts. Allow students with additional needs to verbally explain their conclusion.
• Challenge: Encourage deeper discussion on how circuits in homes use multiple paths (parallel circuits).

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Teacher’s Reflection (Post-Lesson Notes)

• Were students able to accurately describe the effect of resistance?
• Did students confidently use scientific vocabulary?
• How well did the practical activity engage different learning abilities?

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Resources Required

✅ Batteries (Cells)
✅ Bulbs
✅ Switches
✅ Wires with crocodile clips
✅ Printed worksheets for predictions and conclusions

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Final Thought

This lesson balances hands-on engagement with scientific explanations, ensuring that Year 6 students can visualise and understand electrical resistance. The structured approach—predict, observe, explain—supports deep learning and critical thinking while aligning with UK curriculum goals. ✅