Magnetism
1. What is magnet? Write any two properties of magnet.
Ans: Substance which has the property of attraction or repulsion is called magnet.
Properties of Magnet:
- A magnet has two poles: north and south. These poles are situated near the two ends of the magnet.
- A magnet attracts magnetic substance and the attracting force is more at the poles of the magnet than in the material between the poles.
- A freely suspended bar magnet always shows north-south direction when it is at rest.
Ans: Magnet which is formed naturally is called natural magnet. e.g. lodestone.
Man made magnet is called artificial magnet. e.g. bar magnet, U-shaped magnet, horse shoe magnet, etc.
3. What are molecular magnets?
Ans: The molecules of the magnetic substance retain magnetic property. They are called molecular magnets.
4. Write any two methods to conserve the magnetic power.
Ans: The following are the two methods to conserve the magnetic power:
- We should not drop the magnet from height.
- We should not keep the magnets near the fire or hot objects.
- We should not rub the same poles of magnet.
5. What do you mean by magnetic induction? Draw a neat figure of magnet showing magnetic molecules.
Ans: The process of producing the magnetic behavior on a magnet substance when it is brought near to magnet is called magnetic induction.
Or
Development of temporary magnet in any magnetic substances by the help of magnet is called magnetic induction.
6.What is molecular theory of magnetism?
Ans: If molecular magnets align in row, then the substance exhibit magnetic property. Similarly, if they are in close chain, they do not exhibit magnetic property. This is called molecular theory of magnetism.
7. Write any two reasons of loss of magnetic properties of a magnet.
Ans: The following are the two reasons of loss of magnetic properties of a magnet:
- By heating the magnet.
- By passing electric current through the magnet.
8.Mention molecular theory of magnetism. Why magnet has more magnetic force at poles then at its middle portion?
Ans: Molecular theory of magnetism states, "If molecular magnets align in a row, then the substance exhibits magnetic property. Similarly, if they are in close chain, they do not exhibit magnetic property." This is the molecular theory of magnetism.
The molecular magnets are arranged in open chain so that the north pole or south pole of molecular magnets lie in same direction. Which gives strong force at poles where as two opposite poles are arranged at the middle and the force cancel with each other. So, poles have more force than its middle.
9.What are the causes of demagnetization?
Ans: The following are the some causes of demagnetization:
- Dropping regularly from a certain height.
- Hammering a magnet.
- By heating a magnet.
- Rubbing the same pole.
10. What happens when a magnet is heated?
Ans: When magnet is heated, the magnet become demagnetized.
11. Study the given figure and answer the following question.
Name figure A and Figure B.
Ans: Here, A is a magnet and B is magnetic substance.
Which theory indicate the given figure?
Ans:The given figures are based on molecular theory of magnetism.
12. Two poles of a magnet are of equal strength, why?
Ans: Two poles of a magnet are of equal strength because the number of free north poles at one end is equal to the number of free south poles at other end.
13. What do you understand by magnetization and demagnetization?
Ans: The process of making magnet is called magnetization where as the process of losing the magnetic property is called demagnetization.
14. How does a magnet get its magnetic property?
Ans: A magnet has molecules align in same direction which provides the magnetic property to it.
15. Though an iron is made up of molecular magnets, it does not have magnetic property, why?
Ans: Though an iron is made up of molecular magnets, it does not have magnetic property because the molecules of iron are not aligned in same direction and until the molecules are not in same direction substance does not get magnetic property.
16. A magnet gets demagnetized when it is heated or hammered. Explain this statement on the basis of molecular theory of magnetism.
Ans: When a magnet is heated or hammered, molecular vibration occurs inside it which disturbs the regular arrangement of molecules in a magnet. If arrangement of molecules disturb magnetic property is lost so magnet gets demagnetized.
17. How is the state of molecular magnets of magnetic substance laid?
Ans: Molecular magnets of magnetic substance are laid in same direction or open chain.
18. Distinguish between magnet and magnetic substance.
19. Why do the poles of a magnet when broken down into pieces, not get separated from each other?
Ans: The poles of a magnet can not be separated even by breaking into pieces because they exit in pair and every molecules of a magnet has poles in pair.
12. Two poles of a magnet are of equal strength, why?
Ans: Two poles of a magnet are of equal strength because the number of free north poles at one end is equal to the number of free south poles at other end.
13. What do you understand by magnetization and demagnetization?
Ans: The process of making magnet is called magnetization where as the process of losing the magnetic property is called demagnetization.
14. How does a magnet get its magnetic property?
Ans: A magnet has molecules align in same direction which provides the magnetic property to it.
15. Though an iron is made up of molecular magnets, it does not have magnetic property, why?
Ans: Though an iron is made up of molecular magnets, it does not have magnetic property because the molecules of iron are not aligned in same direction and until the molecules are not in same direction substance does not get magnetic property.
16. A magnet gets demagnetized when it is heated or hammered. Explain this statement on the basis of molecular theory of magnetism.
Ans: When a magnet is heated or hammered, molecular vibration occurs inside it which disturbs the regular arrangement of molecules in a magnet. If arrangement of molecules disturb magnetic property is lost so magnet gets demagnetized.
17. How is the state of molecular magnets of magnetic substance laid?
Ans: Molecular magnets of magnetic substance are laid in same direction or open chain.
18. Distinguish between magnet and magnetic substance.
Ans: The following are
the difference between magnet and magnetic substance:
|
S.No |
Magnet |
Magnetic Substance |
|
1 |
It attracts the magnetic substance. |
It does not attract the other magnetic substances. |
|
2 |
The molecules in a magnet are in open chain. |
The molecules in a magnetic substance are in close chain. |
19. Why do the poles of a magnet when broken down into pieces, not get separated from each other?
Ans: The poles of a magnet can not be separated even by breaking into pieces because they exit in pair and every molecules of a magnet has poles in pair.
