2.1 Magnetism

• Magnetic properties of materials; magnetic and non-magnetic materials
• Magnetization and demagnetization
• Magnetic field patterns; poles and shapes of magnets
• Care and storage of magnets; applications of magnets

• explain the magnetic properties of materials
• perform magnetization and demagnetization procedures
• draw magnetic field patterns around a magnet
• care for magnets used in equipment at a workplace
• appreciate the application of magnets in day-to-day life

“What causes magnetism?”

“Why are magnets made in different shapes?”

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1. Magnetism
   40 min · 1 practice tasks · quiz
   The magnetic properties of materials, what causes magnetism, magnetizing and demagnetizing, magnetic poles and field patterns, why magnets are made in different shapes, and how to care for and apply magnets.
2. Magnetic and non-magnetic materials
   40 min · 1 practice tasks · quiz
   A bench test that sorts everyday objects into magnetic materials (iron, steel, nickel, cobalt) and non-magnetic materials, including metals that a magnet does not attract.
3. Types of magnetic behaviour
   40 min · 1 practice tasks · quiz
   Ferromagnetic materials are strongly attracted and can be magnetized; paramagnetic materials are weakly attracted; diamagnetic materials are weakly repelled.
4. Soft iron and hard steel
   40 min · 1 practice tasks · quiz
   Soft iron magnetizes and demagnetizes easily (temporary magnets, cores, keepers); hard steel keeps its magnetism (permanent magnets).
5. What causes magnetism
   40 min · 1 practice tasks · quiz
   Domains are groups of atomic magnets. Lined up, they make a magnet; random, they cancel. Breaking a magnet never produces a single pole.
6. Magnetizing by stroking
   40 min · 1 practice tasks · quiz
   Single-touch, double-touch and divided-touch stroking line domains up in a steel bar or needle. Stroke one way, lift, and test the poles.
7. Magnetizing with a current
   40 min · 1 practice tasks · quiz
   A steel bar inside a solenoid carrying DC becomes a strong, even magnet. Soft iron in the same coil is only a magnet while the current is on.
8. Demagnetizing a magnet
   40 min · 1 practice tasks · quiz
   Heat, hammering east-west, and withdrawing from an AC solenoid jumble domains. AC withdrawal is the controlled workplace method.
9. Poles and the pole law
   40 min · 1 practice tasks · quiz
   A free magnet points north-south. Unlike poles attract, like poles repel. Magnetism is strongest at the ends. Repulsion is the sure test of a pole.
10. The magnetic field of a bar magnet
    40 min · 1 practice tasks · quiz
    A magnetic field is the region where a magnetic force acts. Field lines leave N, enter S, never cross, and crowd at the poles. Filings show shape; a compass shows direction.
11. Field patterns of other magnet shapes
    40 min · 1 practice tasks · quiz
    Verify and sketch the fields of U-shaped, ring and disc magnets using iron filings or a compass, and compare them with the bar-magnet pattern.
12. Why magnets are made in different shapes
    40 min · 1 practice tasks · quiz
    Shape is chosen to put the field where the job needs it: bar for a clear N-S line, horseshoe for a strong gap, ring for motors and speakers, disc for flat latches.
13. Care and storage of magnets
    40 min · 1 practice tasks · quiz
    Store bar magnets in pairs with unlike poles together and soft-iron keepers, lying north-south. Do not drop, heat or hammer them, or park them on cards and phones.
14. Magnets in everyday life
    40 min · 1 practice tasks · quiz
    Compasses, latches, loudspeakers, motors, generators, separators, card strips and MRI all use magnets. Present one application and link it to the next sub-strand, electromagnetism.