Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: derive, using Kirchhoff’s laws, a formula for the combined resistance of two or more resistors in series
Learning Objective/s:
  • Describe Kirchhoff’s Current and Voltage Laws and their relevance to circuit analysis.
  • Explain why the current is identical through all components in a series circuit.
  • Apply KVL and Ohm’s law to derive the series‑resistance formula \(R_{\text{eq}} = \sum R_k\).
  • Solve numerical problems that require calculating equivalent resistance of series resistors.
  • Identify and correct common misconceptions about series circuits.
Materials Needed:
  • Projector or interactive whiteboard
  • Slide deck showing the derivation steps
  • Printed worksheet with guided questions
  • Set of resistors, a battery, and a bulb for a quick demo
  • Calculators for students
  • Whiteboard and markers
 Introduction:
Begin with a brief demonstration of three resistors in series lighting a bulb, asking students what they expect the total resistance to be. Recall the previous lesson on Ohm’s law and introduce Kirchhoff’s laws as the analytical tools needed. State that by the end of the lesson they will be able to derive and apply the series‑resistance formula.
Lesson Structure:
  1. Do‑now (5') – short question on current continuity in series circuits.
  2. Mini‑lecture (10') – review KCL and KVL with simple examples on the board.
  3. Guided derivation (15') – step‑by‑step use of KVL and Ohm’s law; students complete missing steps on the worksheet.
  4. Hands‑on demo (10') – connect three resistors in series, measure voltage drops, and compare with the derived formula.
  5. Misconception check (5') – quick clicker quiz targeting common errors.
  6. Extension activity (5') – pose the parallel‑resistor derivation as a starter for homework.
Conclusion:
Recap that the equivalent resistance of series resistors is the arithmetic sum of the individual resistances, reinforced by the experimental verification. Ask students to write an exit‑ticket sentence summarising the key reasoning behind the formula. Assign a worksheet containing both series and parallel resistance problems for further practice.