FORM TWO PHYSICS STUDY NOTES TOPIC 3-4.

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TOPIC 3: MAGNETISM 

Concept of Magnetism
The Orign of Magnetism
Explain the origin of magnetism
Chinese were the first to use the metal magnetite called lodestone. A Lodestone was capable of attracting small iron pieces and it was used as a crude navigation compass by Greeks. Lodestones were the earliest magnets.
Iron, nickel and cobalt are the only naturally occurring magnetic materials. Magnet has two ends known as magnetic poles in which the greatest attraction power is concentrated.
Magnetic and Non-magnetic Materials/Substances
Identify magnetic and non-Magnetic material/substances
Magnetic substances
These are substances which have a property of being attracted by a magnet.E g; iron,steel,cobalt and nickel.
  • Pole strength refers to the ability of a magnet to attract objects.
  • Ferromagnetic substances have very high magnetic susceptibility (easily magnetized).Eg; iron, nickel and cobalt.
  • Electromagnet is the substance which requires electric current to attain magnetism.
  • Permanent magnet is a substance which is already a magnet and it doesn’t require electric current to attain magnetism.
Non-magnetic substances
These are substances which are not attracted by a magnet.Eg; copper, brass, aluminium,glass,plastic and wood.These substances have very weak magnetic properties.
The Properties of Magnets
State the properties of magnets
Magnets have a tendency of attracting magnetic substances and have no action on non-magnetic materials.
Types of magnetic materials
There are three types of magnetic materials:
  1. Diagmatic materials: Are substances which have a tendency to repel from a stronger to weaker magnetic field. Eg; bismuth, water, gold,air,hydrogen,common salt,diamond,silver and copper.
  2. Paramagnetic materials: Are substances which become weakly magnetized when placed in magnetic field. Eg; aluminium,platinum,chromium,oxygen and manganese.
  3. Ferromagnetic materials: Are substances which becomes magnetized when placed in magnetic field. Their magnetic domain become aligned in one direction when they are placed in magnetic field. Eg; iron, cobalt and nickel.
Magnetic domain refers to the molecular magnets lined up with each other which constitute ferromagnetic materials.
The direction of magnetic poles varies from one domain to another if the magnet is unmagnified
Types of Magnets
Identify types of Magnets
Magnets may also be classified according to their shapes. This includes:
  1. Horse shoe magnet
  2. Rod magnet
  3. Field magnet
  4. Bar magnet
Application of Magnets
Identify application of magnets
Magnets are used in:
  1. women handbags closing
  2. picking up heavy loads
  3. electrical appliances like meter and receivers
  4. sound and video recording equipment
  5. computer memory and disks
  6. electrical trains

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