| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: Define electromotive force (e.m.f.) as the electrical work done by a source in moving a unit charge around a complete circuit |
Learning Objective/s:
- Define electromotive force (e.m.f.) and distinguish it from terminal potential difference.
- Explain how internal resistance affects the terminal voltage of a source.
- Apply the relationship V = e.m.f. – I r to calculate terminal voltage in simple circuits.
- Identify common misconceptions about e.m.f. and correct them.
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Materials Needed:
- Projector or interactive whiteboard
- Printed worksheet with circuit diagram and calculation problems
- Set of AA batteries and a small resistor (for demonstration)
- Multimeter
- Whiteboard markers
- PowerPoint slides summarising definitions and formulas
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Introduction:
Begin with a quick demonstration: connect a 12 V battery to a lamp and ask students what they expect to see on a voltmeter. Recall that they already know voltage is the work per unit charge and that a source supplies energy. State that by the end of the lesson they will be able to define e.m.f., differentiate it from terminal voltage, and use the formula V = e.m.f. – I r.
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Lesson Structure:
- Do‑now (5’) – students answer a short question on the difference between open‑circuit and closed‑circuit voltage on a worksheet.
- Teacher mini‑lecture (10’) – present definitions of e.m.f., potential difference, internal resistance with slides and the key equation.
- Guided demonstration (10’) – use the battery, resistor and multimeter to measure open‑circuit voltage, then connect a load and show the drop; students record values.
- Collaborative problem solving (15’) – groups calculate terminal voltage for given e.m.f., I and r values, then share answers; teacher checks misconceptions.
- Quick check (5’) – exit‑ticket where each student writes the definition of e.m.f. in their own words.
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Conclusion:
Summarise that e.m.f. is the source’s ability to do work on a unit charge and remains constant regardless of load, while the observed terminal voltage decreases due to internal resistance. Ask a few students to share their exit‑ticket definitions to confirm understanding. Assign homework: complete the worksheet’s additional calculation questions and bring a real‑world example of a device where internal resistance is significant.
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