Lesson Plan

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Lesson Plan
Grade: 12 Date: 25/02/2026
Subject: Physics
Lesson Topic: recall and understand that the efficiency of a system is the ratio of useful energy output from the system to the total energy input
Learning Objective/s:
  • Define efficiency as the ratio of useful energy output to total energy input.
  • Calculate the efficiency of a system from given energy data and express it as a percentage.
  • Identify typical sources of energy loss in real‑world systems and explain why efficiency is always ≤ 100 %.
  • Solve practice problems involving electrical, mechanical, and solar systems.
  • Distinguish efficiency from power and address common misconceptions.
Materials Needed:
  • Projector and screen
  • Whiteboard and markers
  • Printed worksheet with efficiency formula and practice questions
  • Calculator (or smartphone calculator)
  • Sample devices (small electric motor, LED bulb) for demonstration
  • Energy‑flow diagram handout
 Introduction:
Imagine a car that uses every drop of fuel to move forward. Students already know the law of conservation of energy and basic power calculations. By the end of the lesson they will be able to state the definition of efficiency, compute it for given situations, and explain why real systems are less than 100 % efficient.
Lesson Structure:
  1. Do‑now (5'): quick quiz on energy conservation concepts.
  2. Mini‑lecture (10'): introduce efficiency definition, formula, and typical values.
  3. Guided worked example (10'): heater problem – students follow step‑by‑step calculations on worksheet.
  4. Hands‑on demonstration (10'): compare a small motor and an LED bulb, discuss observable losses.
  5. Independent practice (15'): students solve the three practice questions while teacher circulates.
  6. Summary check (5'): exit ticket – write one sentence defining efficiency and give one real‑world example.
Conclusion:
We recap that efficiency measures useful output versus total input and that real systems always incur losses. Students submit their exit tickets, demonstrating their understanding. For homework, each student selects a household appliance, finds its power rating and actual useful output, and calculates its efficiency.