| Lesson Plan |
| Grade: Year 10 |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: explain the use of thermistors and light-dependent resistors in potential dividers to provide a potential difference that is dependent on temperature and light intensity |
Learning Objective/s:
- Describe the principle of a potential divider and its equation.
- Explain how thermistors and LDRs change resistance with temperature and light.
- Calculate the output voltage of a sensor‑based divider for given conditions.
- Design a simple voltage‑divider circuit using a thermistor or LDR and select appropriate fixed resistor values.
- Analyse the effect of sensor characteristics on circuit performance.
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Materials Needed:
- Breadboard and jumper wires
- 5 V and 12 V DC power supplies
- NTC thermistor (≈10 kΩ at 25 °C)
- LDR (photoresistor) with known resistance range
- Fixed resistors (1 kΩ–10 kΩ) and a multimeter
- Oscilloscope or data‑logger (optional)
- Projector and slide deck
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Introduction:
Begin with a quick demonstration: connect a simple voltage divider and show how the output voltage changes when a thermistor is heated. Ask students what they recall about resistors in series and voltage division. Explain that today they will explore how temperature‑ and light‑sensitive resistors can be used to create a voltage that varies with environmental conditions, and they will be able to predict and design such circuits.
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Lesson Structure:
- Do‑now (5'): Students answer a short quiz on the voltage‑divider formula (check understanding).
- Mini‑lecture (10'): Review potential‑divider theory and introduce thermistors and LDRs (concept).
- Guided example (15'): Walk through a thermistor calculation for two temperatures; students work in pairs to compute.
- Hands‑on activity (20'): Build two circuits on breadboards – one with a thermistor, one with an LDR – and measure Vout under varying conditions.
- Data analysis (10'): Plot Vout versus temperature/light and discuss trends and sensor characteristics.
- Exit ticket (5'): Write one sentence summarising how sensor resistance influences output voltage.
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Conclusion:
Summarise that the voltage across the sensor resistor reflects the measured physical quantity, and proper resistor selection ensures a usable voltage range. For the exit ticket, students state the key relationship between resistance change and output voltage. Assign homework: design a potential‑divider circuit for a given temperature range and calculate expected Vout values.
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