Interpreting IV Graphs

Overview

This 50-minute lesson for Year 10 students is Lesson 3 of 4 in the unit Circuit Connections Unveiled. Students will analyse and interpret current-voltage (IV) graphs for different circuit components, focusing on resistive and non-resistive behaviours and the significance of graph shapes and slopes. The lesson aligns with the National Curriculum for England (Key Stage 4 Science - Physics): Electricity programme of study, especially understanding current, voltage, resistance and circuit component behaviour (NC ref: KS4 Physics - Electricity 4.4.1 and 4.4.2).

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Learning Objectives (WALT)

• WALT interpret IV graphs for different circuit components.
• WALT understand how the slope and shape of IV graphs relate to component behaviour (Ohmic and non-Ohmic behaviour).
• WALT explain the relationship between current and voltage for resistors, filament bulbs, and diodes.

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Success Criteria

• I can describe the shape of an IV graph for a resistor, filament bulb, and diode.
• I can explain what the slope of an IV graph tells me about the resistance of a component.
• I can compare and contrast the IV characteristics of Ohmic and non-Ohmic components.
• I can interpret real IV graphs and relate their features to circuit components studied.

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Curriculum Links

• Physics 4.4.1: Electrical circuits and component behaviour, including understanding current and voltage and how they vary in circuits.
• Physics 4.4.2: Use IV characteristics to explain component behaviour and resistance changes with voltage/current.
• Working Scientifically: Analyse and interpret data to identify patterns, draw conclusions, and explain phenomena.

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Resources

• Whiteboard & projector
• Printed IV graphs sheets (dyslexia-friendly fonts and colour-coded) for resistor, filament bulb, diode
• Graph paper and pencils
• Tablets/laptops with an online interactive IV graph simulation (optional)
• Laminated success criteria cards
• Differentiated worksheet packs (3 levels)

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Lesson Activities

1. Starter (5 minutes)

Activity: Quick recall and recap

• Teacher asks: What is the relationship between voltage and current in a resistor?
• Students discuss in pairs sharing with whole class.
• Display a simple straight-line IV graph of a resistor; ask students to describe what they notice.
• Recap that straight line = constant resistance (Ohm’s Law).

Differentiation: Sentence starters on board for those who struggle verbally (e.g., "The current increases when...").

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2. Introduction & Direct Teaching (10 minutes)

• Explain IV graphs for three components:

  • Resistor: Straight line through origin (Ohmic conductor).
  • Filament bulb: Curve that steepens then flattens due to temperature changes increasing resistance.
  • Diode: Current flows only in one direction after a certain threshold voltage.

• Use colour-coded diagrams on screen and printed handouts (dyslexia-friendly fonts, off-white background).

• Emphasise the significance of the slope (steeper slope = lower resistance).

• Compare shape differences and explain why the bulb’s resistance increases with temperature (linking to particle physics).

Extension: For advanced learners, briefly introduce the concept of non-linear IV curves and exponential behaviour in diodes.

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3. Main Activity: Group Interpreting IV Graphs (20 minutes)

• Students form groups of 4-5.

• Distribute the differentiated worksheet sets:

  • Support level: Labelled IV graphs with guided questions.
  • Standard level: Graph analysis and interpretative questions.
  • Extension: Predict IV behaviour under different circuit conditions and explain the physics behind changes.

• Each group discusses and annotates the printed graphs:

  • Identify component type by shape.
  • Calculate resistance from slope (for linear parts).
  • Explain non-linear behaviours qualitatively.

• Teacher circulates, probing understanding and offering support.

Differentiation: Use buddy system pairing stronger students with those needing support. Use coloured overlays or large print sheets for dyslexic students. Provide summary sentence frames.

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4. Plenary & Feedback (10 minutes)

• Groups present a quick summary of one IV graph they analysed.

• Class votes on which graph represents which component and why.

• Teacher writes model answers on the board, highlighting key terminology: "Ohmic", "Resistance", "Slope", "Non-linear".

• Quick quiz (written or via interactive quiz apps like Kahoot!) on graph interpretation (e.g., "What happens to current if voltage doubles in a resistor?")

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Assessment

• Formative: Teacher questioning and group discussions during activity.
• Summative: Differentiated worksheet end questions to be marked.
• Self-assessment: Students tick off success criteria cards at end of lesson.

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Differentiation & Inclusion Strategies

• Visual supports: diagrams in dyslexia-friendly format, colour coding, overlays.
• Sentence starters and summary frames for writing support.
• Peer support through structured group work.
• Use of ICT for interactive simulations (visual and kinaesthetic learners).
• Extension tasks for high ability to challenge reasoning and extend conceptual understanding.

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Homework / Extension Task

• Students create their own IV graph for a component of choice (real or imagined), including a written explanation of the shape and what it says about the resistance.
• Advanced: Research and summarise how IV characteristics differ in semiconductor devices (transistors, LEDs).

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Reflection & Next Steps

• Students will use this foundational knowledge to conduct practical investigations of IV characteristics in the next lesson (Lesson 4), comparing experimental data to theoretical graphs.

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This lesson plan fully integrates content from the National Curriculum for England and is tailored to engage, challenge and support Year 10 learners in understanding electrical circuits through interpretative graph skills.