Magnetism

Magnetism

Is the property of a magnet which enables it to attract or repel other metals.

Magnet

Is a piece of metal that attracts other magnetic substances.

What are magnetic materials?
Are materials that can be attracted by a magnet.

They can easily be magnetized.

Examples of magnetic materials

  • Iron (most common magnetic substances)
  • Nickel
  • Cobalt

  • What are non magnetic substances?
    Are substances that cannot be attracted by magnets.
    Examples of non magnetic substances.
  • Dry wood
  • Plastic
  • Lead
  • Glass
  • Cloth
  • Copper
  • Paper
  • Aluminium
  • Brass

Types of magnets.

There are two main types of magnets;
i. Artificial magnets.
ii. Natural magnets.

Artificial magnets


  1. These are magnets made by people.

    Examples of artificial magnets and their shapes.
  2. Bar magnet; This is a bar of uniform cross section. It may be rectangular or circular.
bar magnet
  • Horse shoe magnet; It has u shape.
horse shoe magnet
  • Needle magnet; It has a thin pointed at both ends and balanced at the centre.
needle magnet
  • Electromagnet
electro magent
  • Natural magnets
    They don’t lose magnetism.

Examples of natural magnets.

  •  The Earth; It is a huge natural magnet. Its magnetic field is weak, that is why you can’t feel it.
earth
  • Lodestone/magnetite; Lodestone is a magnetic ore which occurs naturally in the earth. It was discovered near the ancient city of magnesia in Asia Minor. It was the first magnet to be discovered by people.

Properties of magnets

  •  Like poles of a magnet repel.
like pole
  •  Unlike poles attract each other.
unlike pole
  •  When a magnet is freely suspended by a piece of thread it will always rest in the north –south direction.
north direction
  • The poles are the strongest part of the magnet.
iron feelings
  •  Magnets have magnetic fields around them.
line of forse
  •  Magnetism passes through non magnetic materials like wood and paper.
wood and paper
  • Broken pieces of magnets regain their poles.
broke magnet
  •  Magnets become weaker with age.

Preventing magnets from losing magnetism.

  •  Keep them using iron keepers.
iron keeper

Laws of magnets

  • Like poles of a magnet repel each other while unlike poles attract each other.

What is magnetic field?
It is the area around the magnet in which it can attract other magnetic materials.

Properties of magnetic fields.

  • They originate from North Pole and end at the South Pole.
  • The lines forces do not intersect with each other.
  • A line of force is continuous; it starts from the North Pole and ends at the south pole.
  • There is no line of force within the magnet itself

Methods of making magnets.

  •  Stroking by single touch:

   It is stroking by single touch method because one magnet is used.

Note. The end after the stroke becomes the opposite pole of the magnet being used.

steel bar

Stroking by double/divided touch

It is so because two magnets are used.

steel
  • By induction A magnetic object becomes magnetized by induction when it is nearer or contact with a magnet.
last

Lesson five and six ) week three

  • By electrical method
    This is a method of making magnets using electricity

A magnet made by using electricity is electro- magnet.

cirt

Electro magnets are made stronger by;

  • By increasing the coils around the soft iron
  • By increasing the voltage (electrical strength

Determining the poles an electromagnet.

  1. The direction of flow of current.
  2. Looking at it from either end;
    1. If current flows in an anticlockwise way through the solenoid, the pole is North (N)
    1. If current flows in a clockwise way through the solenoid, the pole is South(S).

ii. Using the right hand grip rule.

  • Grasp the solenoid in the right hand with thumb pointing in the direction of current.
  • The thumb points to the North Pole.