| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: define capacitance, as applied to both isolated spherical conductors and to parallel plate capacitors |
Learning Objective/s:
- Define capacitance and express it as the ratio Q/V.
- Derive the capacitance formula for an isolated spherical conductor.
- Derive the capacitance formula for a parallel‑plate capacitor, including the effect of a dielectric.
- Compare how geometry and dielectric constant influence capacitance.
- Apply the formulas to calculate capacitance in numerical examples.
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Materials Needed:
- Projector or interactive whiteboard
- PowerPoint slides with sphere and parallel‑plate diagrams
- Worksheet containing worked examples
- Scientific calculators or simulation app
- Rulers/scale for drawing plate dimensions (optional)
- Physical capacitor models or 3‑D printed sphere for demonstration
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Introduction:
Begin with a quick question: “If you double the charge on a capacitor, what happens to its voltage?” Students recall the Q = CV relationship, setting the stage for a precise definition of capacitance. Explain that today they will see how geometry alone determines C for two classic configurations, and they will be able to predict C before measuring it.
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Lesson Structure:
- Do‑now (5'): Students write the definition C = Q/V on a sticky note and submit.
- Mini‑lecture (10'): Introduce capacitance concept, derive C = 4πϵ₀R for an isolated sphere, emphasise geometry.
- Guided derivation (10'): Derive C = ϵ₀κA/d for a parallel‑plate capacitor, discuss role of dielectric constant.
- Worked example – sphere (8'): Solve the 5 cm radius problem together, check units.
- Worked example – parallel plates (8'): Solve the 0.02 m², 1 mm, κ = 2.5 problem, highlight impact of κ.
- Think‑pair‑share (9'): Students complete a comparison table (geometry vs. C) and answer a short formative quiz on the board.
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Conclusion:
Recap the two formulas and the key geometric dependencies. Students complete an exit ticket stating one way to increase capacitance for each configuration. Assign homework: calculate the capacitance of a spherical conductor of radius 10 cm and a parallel‑plate capacitor with A = 0.05 m², d = 2 mm, κ = 1.
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