Lesson Plan

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Lesson Plan
Grade: Date: 25/02/2026
Subject: Physics
Lesson Topic: Know that a current-carrying coil in a magnetic field may experience a turning effect and that the turning effect is increased by increasing: (a) the number of turns on the coil (b) the current (c) the strength of the magnetic field
Learning Objective/s:
  • Describe the principle of the magnetic turning effect on a current‑carrying coil.
  • Explain how the number of turns, current, and magnetic field strength affect the torque.
  • Calculate the torque produced by a rectangular coil using τ = N B I A sinθ.
  • Identify the function of a split‑ring commutator in a DC motor.
Materials Needed:
  • Projector or interactive whiteboard
  • Printed diagram of a simple DC motor
  • Coil, permanent magnets, and split‑ring commutator (demo kit)
  • Stopwatch
  • Worksheet with torque calculation problems
  • Calculator
 Introduction:
Begin with a quick demonstration of a small hand‑held motor turning when powered, asking students what they think causes the motion. Review prior learning on magnetic force on a straight conductor and the right‑hand rule. State that by the end of the lesson they will be able to predict and calculate the turning effect of a coil and explain the role of the commutator.
Lesson Structure:
  1. Do‑now (5') – Students answer a short question on magnetic force on a straight wire.
  2. Mini‑lecture (10') – Derive the torque formula τ = N B I A sinθ with diagrams.
  3. Guided practice (10') – Work through the sample exam problem together, highlighting each factor.
  4. Hands‑on demonstration (15') – Set up the DC motor kit; students vary N, I, and B and record observations.
  5. Group activity (10') – Calculate torque for different scenarios on the worksheet.
  6. Check for understanding (5') – Exit ticket: one sentence describing why the commutator is needed.
Conclusion:
Summarise that torque increases proportionally with the number of turns, current, and magnetic field strength, and that the commutator maintains unidirectional rotation. Ask students to write an exit ticket stating the purpose of the commutator. Assign homework to design a simple motor diagram and compute its maximum torque for given values.