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Fun with Magnets Class 6 Notes




DISCOVERY OF MAGNETS

  • Some people said a natural magnet was discovered by Greeks called magnetite.
  • An ancient tale of Greek divulged that a shepherd boy named “Magnes” discovered the magnet when he was roaming nearby a mountain carrying a wooden stick having metal cap at the bottom stuck to the black rock, which was named after him “Magnetite”.
  • Nowadays, magnets are used to make televisions, telephones, mobile devices and washing machines, etc
 

MAGNET

  • A magnet is a substance that has the capability of attracting the substances like iron, nickel and cobalt(Figure 1).
  • The property of attracting other substances such as iron, nickel and cobalt of a magnet is called magnetism.
  • The force produced by the magnet to attract the other substances is called magnetic force.
  • The region around the attraction of the substance and a magnet by magnetic force. Such a region is called a magnetic field.
 
 

Magnetic and Non-Magnetic Substances

 
Magnetic Substances
Non-Magnetic Substances
These substances that are attracted towards the magnet.
These substances do not attract towards the magnet.
Iron, nickel and cobalt are the examples of magnetic substances.
Copper, brass and wood are the examples of non-magnetic substances.
 

NATURAL AND ARTIFICIAL MAGNETS

 
Natural Magnets
Artificial Magnets
The magnets are created by the nature are called natural magnets(Figure 2 a).
The magnets that are created by man are called artificial magnets(Figure 2 b).
A certain types of rocks such as magnetite are the examples of natural magnets.
Bar magnets, horseshoe magnets and cylindrical magnets are the examples of artificial magnets.
They are present in irregular shapes.
They are constructed in different shapes and sizes.
They are made up of rocks.
They are made up of iron, cobalt and nickel.

Figure 2: Types of magnets: a) Natural; b) Artificial.
 

PROPERTIES OF A MAGNET

The Attractive Property

The property of a magnet attracting the magnetic substances towards itself even if they are placed between the non-magnetic substance. Such property of a magnet is known as the attractive property. For example, a magnet can attract an iron hook that is placed under the wooden table corner.

Poles of a Magnet

  • The two ends of a magnet are known as magnet poles.
  • The force of the magnet is at the maximum level at the magnetic poles.
  • The force of a magnet is minimum in the middle.
  • These magnetic poles of every magnet are called the North Pole and the South Pole(Figure 1 mentions the magnetic poles).
  • The North Pole of every magnet faces the earth’s geographical north pole, while its South Pole faces the earth’s geographical south pole.
 

The Directive Property

If we freely suspend a bar magnet then its poles are always aligned in the geographical north-south directions.
Due to this property, people started using a magnet as a directional tool and called it lodestone(leading stone).
Magnetic axis: The two poles of a magnet adjoined at an imaginary line called a magnetic axis. The axis of a magnet is always aligned in the north-south directions when the magnet is freely suspended.
Magnetic compass: A device that was invented to find the directions by the sailors, pirates and boat travellers composed of the magnetic needle with two-point ends suspended on a pivot where it is free to rotate(Figure 3).

Figure 3: A magnetic compass.
 

Separating Two Poles of a Magnet

The magnetic poles of a magnet cannot be separated even if the magnet is broken down into several pieces. They always present as a pair in a magnet.
 

Attraction and Repulsion of Magnetic Poles

When we place two magnets in such a way where their adjacent poles are similar, then they try to move away from each other. While, if opposite poles of magnets are placed adjacent to each other, they attract each other(Figure 4).
 North PoleNorth Pole repels each other.
South PoleSouth Pole repels each other.
North PoleSouth Pole attracts each other.
South PoleNorth Pole attracts each other.
 

Figure 4: Attraction and Repulsion property of magnets.
 

Test for magnetism

To identify whether a substance is either magnet or not. We perform the following steps:-
  • Check whether a substance is attractive to the Alnico (iron alloys) or not.
  • Suspend a substance and see whether its poles aligned to the north-south directions or not.
  • Check whether its two poles are separating or not.
  • Check whether it attracts towards the opposite pole and repels to the same pole.
 

MAKING MAGNETS

  • We create magnets by using magnet substances. This process of making magnetic substances is called magnetisation.
  • A magnet can be either temporary or permanent.
  • Temporary magnets lose their magnetism concerning the time of their use. Iron, nickel and cobalt are used to make temporary magnets.
  • Permanent artificial magnets cannot lose their magnetism even after the removal of their cause of magnetism. The mixtures of iron, cobalt and nickel with the other elements form permanent magnets.
The methods of making a magnet are:-
i. Single-touch Method
In this method, a bar magnet is used to make magnets. Rub the bar magnet on the iron from one end to the other end at least 40 times. The initial rubbing end becomes iron’s the North Pole and another end becomes the South Pole(Figure 5).

Figure 5: Single-touch Method for making magnets.
 
ii. Double-touch Method
In this method, we use two magnets. Both magnets are slowly rubbed but by their opposite poles on the iron. Remember only to use the same strength magnets such as iron bars . The initial rubbing end would be the North Pole and another end would be the South Pole.
Nowadays, magnets are also created by using electric current. Both permanent and temporary magnets can be created by using electric current. For example, an electromagnet is a temporary magnet.
 

EARTH AS A GIANT MAGNET

A freely suspended magnet’s poles align to the north-south directions shows that the earth is another magnet from which it's attracted to. The geographical North Pole of the earth is placed near the South Pole of the magnet and the geographical South Pole of the earth is located near the North Pole of the magnet
 

PRESERVING MAGNETS

If a magnet is hammered, heated or fallen to the ground, then it loses its magnetism. This phenomenon is called demagnetisation. Even if two magnets are placed adjacent to each other by their opposite poles, they lose their magnetism.
To store magnets carefully, we should follow the following steps:-
  • Keep bar magnets in a wooden box with unlike poles with the same side
  • Put a piece of a wood between two magnets to separate them.
  • Place magnetic keepers(soft iron bars) to the ends of the both magnets.
  • Use magnets often to prevent them from self-demagnetisation(a phenomenon in which magnets lose their magnetism without getting used over a long period of time).
  Important Note: Do not go near or inside the MRI room by taking magnets with you.

 

USES OF MAGNETS

The uses of magnets are:-
  • They are used in the refrigerator doors to close automatically.
  • The information of credit and debit cards is stored in the magnetic strip present on them.
  • They are used to produce storing devices such as hard discs.
  • They are used to separate magnetic substances from a mixture.
  • They are used to construct various medical machines such as Magnetic Resonance Imaging(MRI).
  • They help dynamo to generate electricity.
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Class 6 Maths Class 6 Science

Practice Question

Question 1 What is $\frac {1}{2} + \frac {3}{4}$ ?
A)$\frac {5}{4}$
B)$\frac {1}{4}$
C)$1$
D)$\frac {4}{5}$
Question 2 Pinhole camera produces an ?
A)An erect and small image
B)an Inverted and small image
C)An inverted and enlarged image
D)None of the above