| Lesson Plan |
| Grade: |
Date: 25/02/2026 |
| Subject: Physics |
| Lesson Topic: State that the combined resistance of resistors in parallel is less than that of any single resistor in that circuit |
Learning Objective/s:
- Describe how resistors behave in parallel circuits.
- Explain why the equivalent resistance of parallel resistors is always less than any individual resistor.
- Apply the reciprocal formula to calculate equivalent resistance for two or more resistors.
- Analyse a worked example and interpret the result in relation to the individual resistances.
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Materials Needed:
- Projector or interactive whiteboard
- Printed worksheets with parallel‑circuit diagrams
- Set of resistors and a breadboard for demonstration
- Multimeter
- Calculator or spreadsheet software
- Formula summary handout
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Introduction:
Imagine you need to power several bulbs from a single battery and want each bulb to shine equally bright. Students will recall that in series circuits the same current flows through each component, and they will be told the success criteria: they must be able to state the parallel‑resistance rule and calculate the equivalent resistance for a given set of resistors.
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Lesson Structure:
- Do‑now (5'): Quick quiz on series‑circuit concepts to activate prior knowledge.
- Mini‑lecture (10'): Review series behaviour, introduce parallel circuits, and present the reciprocal formula.
- Guided demonstration (10'): Build a three‑resistor parallel circuit on a breadboard, measure voltages and currents, and discuss observations.
- Worked example (10'): Step‑by‑step calculation of equivalent resistance for 12 Ω, 18 Ω, and 30 Ω resistors; students follow on their worksheets.
- Pair activity (10'): Students calculate equivalent resistance for two new sets of resistors and compare results, noting why the value is always lower.
- Concept check (5'): Think‑pair‑share answering “Why does adding another parallel resistor always decrease the total resistance?”
- Summary & questions (5'): Teacher recaps key points and addresses any misconceptions.
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Conclusion:
We recap that the equivalent resistance of a parallel network is always smaller than the smallest individual resistor and review the reciprocal method. For the exit ticket, each student writes the equivalent resistance for a given three‑resistor set and explains in one sentence why it is lower. Homework: complete a worksheet with mixed series‑and‑parallel problems, including at least one real‑world scenario.
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