Magnetism

Grade 12 · Physics

Semester 1 | Period 3 | Week 13

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Subject: Physics

Semester: 1

Period: 3

Week: 13

School Name:

Teacher’s Name:

Subject: Physics

Grade Level: Grade 12

Week & Period: Week 13, Period III

Date:

Topic: Magnetism
Sub-Topic: Magnets – Types, Properties, and Magnetic Materials

Learning Objectives:

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

  1. Define magnetism and describe natural and artificial magnets.
  2. Identify the properties of magnets.
  3. Differentiate between magnetic and non-magnetic materials.
  4. Describe magnetic poles and their interactions.
  5. List methods of magnetization and demagnetization.

 

Instructional Materials:

  • Bar magnets
  • Steel and iron rods
  • Paper clips
  • Compass
  • Iron filings
  • Hammer
  • DC power supply with solenoid
  • Magnetic stirrers
  • Sandpaper

 

Anticipation (Warm-Up Activity):

Ask learners:

"Have you ever used a magnet to pick up metal objects? Why does it work on some metals and not others?"
Demonstrate using a bar magnet to pick up iron nails and compare with aluminum foil.

 

Building Knowledge (Main Lesson):

  1. What is Magnetism?

Magnetism is a physical phenomenon produced by the motion of electric charge, resulting in attractive or repulsive forces between objects.

  1. Types of Magnets:
  • Natural magnets (e.g., lodestone) occur in nature and are weak.
  • Artificial magnets (e.g., bar magnets, horseshoe magnets, electromagnets) are man-made and more powerful.
  1. Properties of Magnets:
  • Attraction: Magnets attract ferromagnetic materials like iron, cobalt, and nickel.
  • Repulsion: Like poles repel; unlike poles attract.
  • Magnetic poles: Every magnet has two poles—North and South. Poles always exist in pairs.
  • Magnetic field: Invisible field around a magnet where magnetic force is exerted.
  • Retentivity: Ability to retain magnetism. Steel has high retentivity, iron has low retentivity.
  1. Magnetic vs Non-Magnetic Materials:
  • Magnetic: Iron, nickel, cobalt
  • Non-Magnetic: Copper, aluminum, plastic, wood

 

Activities/Experiment:

Experiment 1: Identifying Magnetic Materials

Materials: Paper clips, aluminum foil, steel nail, copper wire, wood splinter, magnet
Procedure:

  • Bring a bar magnet near each material.
  • Record which materials are attracted.

Observation:

  • Iron nail and paper clip are attracted
  • Others are not

Conclusion:
Only ferromagnetic materials respond to magnetic force.

 

Experiment 2: Making a Temporary Magnet

Method: Contact method
Materials: Steel rod, bar magnet
Procedure:

  • Rub one end of the bar magnet along the steel rod in one direction 20–30 times
  • Bring the rod near paper clips

Observation:

  • The rod now attracts paper clips

Conclusion:
The steel rod has become a temporary magnet.

 

Experiment 3: Demagnetization by Heating

Materials: Bar magnet, candle flame
Procedure:

  • Heat one end of the bar magnet until red hot
  • Cool and test if it still attracts iron filings

Observation:

  • Magnet loses strength or becomes demagnetized

Conclusion:
Heating disturbs magnetic domains and causes demagnetization.

 

Assessment (Class Work):

  1. Define magnetism.
  2. State two differences between magnetic and non-magnetic materials.
  3. List and explain two methods of making magnets.
  4. Describe how heating can demagnetize a magnet.
  5. What are the characteristics of magnetic poles?

 

Homework:

  • Sketch and label the magnetic field around a bar magnet using iron filings and a compass.
  • Write a short paragraph on why steel is used to make permanent magnets while soft iron is used for temporary magnets.

 

Expanded Notes:

  • A magnetic field can be visualized by sprinkling iron filings around a bar magnet on paper.
  • Compass needles align with Earth’s magnetic field.
  • Common uses of magnets: compasses, refrigerator doors, electric motors, credit card strips.

 

Differentiation:

  • Use hands-on activities for kinesthetic learners.
  • Visuals and diagrams for visual learners.
  • Group discussions and quizzes for auditory learners.

 

Teacher’s Reflection:

  • Were students able to observe magnetic properties accurately during experiments?
  • Did learners effectively distinguish magnetic from non-magnetic materials?
  • How well did they grasp the concept of magnetization and demagnetization?