| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: understand that the resistance of a thermistor decreases as the temperature increases (it will be assumed that thermistors have a negative temperature coefficient) |
Learning Objective/s:
- Describe how resistivity and conductor geometry determine resistance.
- Explain the exponential decrease of NTC thermistor resistance with rising temperature using the β‑parameter equation.
- Calculate the resistance of an NTC thermistor at a specified temperature.
- Interpret a resistance‑versus‑temperature graph for an NTC thermistor.
- Design a simple temperature‑sensing circuit employing an NTC thermistor.
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Materials Needed:
- Projector or interactive whiteboard
- Thermistor datasheet (NTC type)
- Worksheet with calculation and graphing tasks
- Graph paper or digital plotting tool
- Scientific calculators
- Basic circuit components (breadboard, power supply, multimeter) for demonstration
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Introduction:
Begin with a quick demonstration: heat a thermistor with a hair‑dryer and observe the voltage drop on a multimeter. Ask students what they expect to happen based on prior knowledge of resistors and temperature. Clarify that today they will investigate why NTC thermistors behave opposite to metal resistors and identify the success criteria: explain the concept, perform a calculation, and sketch the characteristic curve.
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Lesson Structure:
- Do‑now (5’) – short question on temperature effects for metals vs semiconductors.
- Mini‑lecture (10’) – review resistivity, R = ρL/A, and introduce the NTC β equation.
- Guided example (12’) – work through the sample calculation (R₀ = 10 kΩ, β = 3500 K, T = 350 K) and a similar practice problem.
- Interactive simulation (8’) – use a web app to vary temperature and plot the exponential resistance curve; record observations.
- Small‑group activity (10’) – design a voltage‑divider circuit that shows a measurable voltage change between 20 °C and 40 °C; present rationale.
- Check for understanding (5’) – exit ticket: one sentence explaining why NTC resistance falls with temperature and one real‑world application.
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Conclusion:
Summarise that resistance depends on both material properties and temperature, with NTC thermistors showing a rapid exponential drop as they warm. Students submit an exit ticket summarising the key principle and receive a homework task to calculate resistance at two additional temperatures and sketch the curve. Reinforce that this knowledge underpins temperature‑sensing circuits in everyday devices.
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