| Lesson Plan |
| Grade: Year 10 (IGCSE) |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Sketch and explain the current-voltage graphs for a resistor of constant resistance, a filament lamp and a diode |
Learning Objective/s:
- Describe the linear I‑V relationship for a constant‑R resistor and identify the slope as 1/R.
- Explain why the I‑V curve of a filament lamp bends as voltage increases.
- Interpret the three‑region I‑V characteristic of a diode, including the “knee” voltage.
- Sketch accurate I‑V graphs for each component and label key features.
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Materials Needed:
- Projector and screen
- Whiteboard and markers
- Worksheet with blank I‑V graphs
- Resistor (known resistance)
- Filament lamp (incandescent bulb)
- Silicon diode
- Variable DC power supply
- Multimeter (voltage & current)
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Introduction:
Ask students to predict how the current will change as the voltage is increased across a resistor, a lamp, and a diode. Review Ohm’s law and the expectation of a straight‑line I‑V graph for an ideal resistor. State that by the end of the lesson they will be able to sketch each graph and explain the physical reasons for its shape.
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Lesson Structure:
- Do‑now (5'): Students sketch an I‑V graph for a resistor on a scrap sheet.
- Mini‑lecture (10'): Review Ohm’s law, linear graphs, and introduce non‑ohmic behaviour.
- Resistor demonstration (15'): Set up a resistor circuit, vary voltage, record I, plot on board.
- Filament lamp activity (15'): Connect lamp to power supply, observe curvature as it heats, discuss temperature‑dependent resistance.
- Diode investigation (15'): Show forward and reverse bias, identify knee voltage (~0.6 V), sketch three‑region graph.
- Guided practice (10'): Students complete worksheet comparing the three graphs, labeling slopes and regions.
- Exit ticket (5'): Quick draw of one I‑V graph from memory with one explanatory sentence.
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Conclusion:
Recap the key differences between the three I‑V characteristics and the reasons behind their shapes. Collect exit tickets to check immediate understanding, and assign homework to finish the worksheet and prepare a short paragraph explaining why a filament lamp’s resistance changes with temperature.
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