Electromagnetic Induction

Grade 12 · Physics

Semester 1 | Period 3 | Week 17

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Subject: Physics

Semester: 1

Period: 3

Week: 17

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 12

Week & Period: Week 17, Period III

Date:

Topic: Electromagnetic Induction
Sub-Topic: Inductors, Generators, Motors, and Transformers

Learning Objectives:

By the end of the lesson, learners should be able to:

  1. Define and explain the function of inductors.
  2. Differentiate between electric generators and electric motors.
  3. State the working principles of motors and generators.
  4. Describe the structure and operation of a transformer.
  5. Distinguish between step-up and step-down transformers.
  6. Solve basic calculation problems involving transformer efficiency and voltage/current ratios.

Instructional Materials:

  • Simple inductor coil
  • DC motor kit
  • AC generator model
  • Laminated iron core
  • Primary and secondary coil wires
  • Power source
  • Multimeter or galvanometer
  • Connecting leads and resistors
  • Transformer diagram charts

 

Anticipation (Warm-Up Activity):

Ask:

“How does a fan spin with electricity while a generator gives electricity when spun?”
Display simple motor and generator models. Let learners observe motion and current generation.

Building Knowledge (Main Lesson):

  1. Inductors
  • Devices that store energy in magnetic fields when current flows through them.
  • Symbol: L, Unit: Henry (H)
  • Applications: in filters, tuning circuits, and transformers.

 

  1. Electric Generator
  • Converts mechanical energy → electrical energy using electromagnetic induction.
  • Principle: Faraday’s Law
  • Components: rotor, stator, magnets, coils
  • Types:
    • AC Generator (Alternator): Produces alternating current.
    • DC Generator: Produces direct current (uses a commutator).
  1. Electric Motor
  • Converts electrical energy → mechanical energy
  • Principle: Force on a current-carrying conductor in a magnetic field
  • Types:
    • AC Motors
    • DC Motors

Key Difference:

  • Generator: motion → electricity
  • Motor: electricity → motion

 

  1. Transformer
  • Device that changes the voltage of AC.
  • Step-up: increases voltage
  • Step-down: decreases voltage
  • Works on mutual induction (changing current in primary → induces voltage in secondary coil)
  • Formula:

   

Activities/Experiments:

Experiment: Step-Up vs Step-Down Transformer

Materials: Laminated iron core, insulated wire, voltmeter, AC source
Procedure:

  • Wind two coils on opposite sides of iron core
  • Connect primary coil to AC source
  • Connect voltmeter across secondary coil
  • Measure voltage with different turn ratios
    Observation:
  • More turns in secondary → voltage increases (step-up)
  • Fewer turns in secondary → voltage decreases (step-down)

 

Experiment: Demonstrating Motor vs Generator

Motor Setup:

  • Connect DC supply to coil in magnetic field → coil rotates

Generator Setup:

  • Rotate coil in magnetic field → connect to galvanometer → needle deflects

 

Sample Problem:

Question:
A transformer has 400 turns in the primary coil and 100 turns in the secondary. If the input voltage is 240V, find the output voltage.

Solution:

Assessment (Class Work):

  1. What is the major function of an inductor?
  2. Differentiate between AC and DC generators.
  3. A transformer has 800 turns in the primary and 200 in the secondary. If 220V is supplied to the primary, find the output voltage.
  4. Explain why transformers cannot work with DC.
  5. List two differences between a motor and a generator.

 

Homework:

  • Draw a labeled diagram of a step-up transformer.
  • Compare the working principles of a motor and a generator in a tabular format.
  • A step-up transformer has a 2:1 turn ratio and receives 100V. What’s the output voltage?

 

Expanded Notes:

  • Transformers rely on alternating current to create varying magnetic flux.
  • Motors are used in blenders, fans, cars; generators in power plants.
  • Inductors resist changes in current, useful in circuits with voltage surges.
  • Efficiency in real transformers is affected by heat, core type, coil resistance.

 

Differentiation:

  • Use animations to show the difference between step-up and step-down
  • Allow students to simulate transformer coil winding
  • Visual analogies for inductors as "shock absorbers" in current flow

 

Teacher’s Reflection:

  • Were learners able to relate theory to the practical models?
  • Did they accurately apply the transformer equations?
  • Was the difference between motors and generators clearly understood?