Lesson Plan

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Lesson Plan
Grade: Date: 17/01/2026
Subject: Physics
Lesson Topic: Calculate the combined resistance of two resistors in parallel
Learning Objective/s:
  • Describe the concept of equivalent resistance for parallel resistors.
  • Apply the formula \(R_{eq} = \dfrac{R_1 R_2}{R_1 + R_2}\) to calculate the combined resistance of two resistors.
  • Analyse circuit diagrams to identify parallel connections and predict current distribution.
Materials Needed:
  • Projector or interactive whiteboard
  • Power supply and breadboard
  • Two resistors (e.g., 120 Ω and 80 Ω) plus additional resistor set
  • Multimeter
  • Worksheet with practice problems
  • Calculator
 Introduction:
Begin with a quick demonstration of two resistors connected to a battery, asking students what they notice about the voltage across each branch. Recall Ohm’s law and the definition of resistance from previous lessons. Explain that by the end of the session they will be able to calculate the equivalent resistance of any two‑resistor parallel network.
Lesson Structure:
  1. Do‑now (5'): Students answer a short recall question on series resistance displayed on the board.
  2. Mini‑lecture (10'): Review voltage equality in parallel branches and derive the parallel‑resistance formula.
  3. Guided practice (12'): Work through the worked example (120 Ω & 80 Ω) together, emphasizing substitution steps.
  4. Hands‑on activity (15'): In pairs, build a parallel circuit on a breadboard, measure branch currents with a multimeter, and compute \(R_{eq}\).
  5. Independent practice (10'): Complete a worksheet with three practice questions while the teacher circulates to address misconceptions.
  6. Check for understanding (5'): Exit ticket – write the formula and one key condition for its use.
Conclusion:
Summarise that parallel resistors share the same voltage and their combined resistance is always lower than the smallest individual resistor. Students submit an exit ticket stating the formula and a brief explanation of why it works. For homework, assign additional problems requiring calculation of equivalent resistance for various two‑ and three‑resistor parallel networks.