Magnets

 


MAGNETS


Magnets are made of materials that possess attractive property and directional property.

 

Attractive Property:

Attracts objects made of iron and nickel or their mixtures/alloys

Iron fillings attracted to the bar magnet

Magnet attracting pieces of iron nails

 

Directional Property:

When suspended freely, magnet orients itself in one particular geographical direction

Substances like iron, nickel and cobalt are strongly attracted to magnets. Substances which are strongly attracted to magnets are called magnetic/magnetic materials.

         

      Iron                         Nickel                      Cobalt

Not all substances are attracted to magnet, such as wood, plastic etc. Such materials are called non-magnetic.

   

Plastic                      Wood

 

Size and Shape of Magnets:

Earlier it was believed that magnets can obtained only naturally in the form of certain rocks that have the property of attraction and direction. These naturally occurring stones or pieces of rock are called natural magnets.

Magnets can be prepared from pieces of iron in various size and shape with a process of magnetization. These magnets are called artificial magnets.

         

       Bar shaped magnet        Cylindrical shaped magnet

                  

                    Ball shaped magnet              Horse-Shoe shaped magnet

We can make artificial magnets from magnetic substance like iron using current. The loops of magnetic field is shown in the figure below to indicate that the substances inside the current carrying coil is magnetised.

 

Types of magnets:

There are two types of magnets: temporary magnets and permanent magnets

 

Temporary magnets:

They retain their magnetic properties only for short period of time.

They are usually made of iron, cobalt, or nickel.

These materials behave like magnets only when they are near to a strong magnet and loose their magnetic property if strong magnet is removed.

 

Permanent magnets:

They retain their magnetic properties for long period of time.

They are made from mixtures of iron, cobalt or nickel with other materials.

 

Electromagnets:

An electromagnet is a special type of magnet in which magnetism is produce by flow of electricity. Unlike a permanent magnet, the strength of an electromagnet can easily be changed by changing the amount of electric current that flows through it. The poles of an electromagnet can even be reversed by reversing the flow of electricity.

A piece of iron bar with a wire wound around it acts as an electromagnet when current passes through it. A piece of iron bar behaves like a magnet only as long as wire wound over it carries current. Its magnetism is lost when the current in the wire is switched off. It is used in electric motors, doorbells, etc.