# Magnetism Exe-10A Short Answer Concise Physics ICSE Class-9 Selina Publishers

Magnetism Exe-10A Short Answer Concise Physics ICSE Class-9 Selina Publishers. There is the solutions of Short Answer type Questions of Induced Magnetism and Neutral Points. Answer of questions Chapter 10 Magnetism your latest textbook which is applicable in 2024-25 academic sessionVisit official Website CISCE for detail information about ICSE Board Class-9

## Magnetism Exe-10A Short Answer Concise Physics ICSE Class-9 Selina Publishers

 Board ICSE Class 9 Subject Physics Writer / Publication Concise selina Publishers Chapter-10 Magnetism Exe-10A Induced Magnetism and Neutral Points Topics Solution of Exe-10(A) Short Answer Type Academic Session 2024-2025

### Induced Magnetism and Neutral Points

Magnetism Exe-10A Short Answer Physics ICSE Class-9 Selina Publishers

page -231

##### Que-1: What is a lodestone?

Ans- Lodestone is an ore of iron oxide (Fe3O4). This ore attracts small pieces of iron and it sets itself along a definite direction when it is suspended freely. It is a natural magnet which was used for the navigation by the marines.

##### Que-2: What is a natural magnet? State two limitations of a natural magnet

Ans- The pieces of lodestone found in nature are called the natural magnets. Limitations of a natural magnet are as listed below: (i) They are irregular and odd shaped. (ii) They are not magnetically very strong.

##### Que-3: What is an artificial magnet? State two reasons why do we need artificial magnets?

Ans- An artificial magnet is a magnetized piece of iron (or other magnetic material). Artificial magnets are required because natural magnets have odd and irregular shape and they are not magnetically very strong. Artificial magnets can be given desired shape and made very strong.

##### Que-4: How will you test whether a given rod is made of iron or copper?

Ans- Iron rod is magnetized when placed near a bar magnet by magnetic induction, while copper rod is not magnified.

##### Que-5: Explain the term induced magnetism.

Ans- The magnetism acquired by a magnetic material when it is kept near (or in contact with) a magnet, is called induced magnetism.

##### Que-6: Explain the following :
###### (c) The north end of a freely suspended magnetic needle gets attracted towards a piece of soft iron placed a little distance away from the needle.

Ans- (a) When  two pins are hung by their heads from the same pole of a magnet, they acquire same polarity. Because like poles repel each other, their pointed ends move apart.

(b) Several  soft iron pins can cling one below the other from the pole of a magnet because the magnet induces magnetism in an iron nail which gets attracted by the magnet and clings to it.
(c) When a piece of soft iron is placed a little distance away from the needle, the needle induces magnetism to the piece of soft iron. Thus, soft iron piece starts behaving like a magnet and it attracts the magnetic needle towards it.
##### Que-7: ‘Induced magnetism is temporary’ Comment on this statement.

Ans- Induced magnetism is temporary as it lasts as long as the magnet causing induction remains in it vicinity.

##### Que-8: ‘Induction precedes attraction’. Explain the statement.

Ans- When a piece of magnetic material is brought near a magnet, it first becomes a magnet by induction and then it is attraction. Thus, we say that induction precedes attraction.

##### Que-9: What do you understand by the term magnetic field lines?

Ans- A magnetic field line is a continuous curve in a magnetic field such that tangent at any point of it gives the direction of the magnetic field at that point.

##### Que-10: State four properties of magnetic field lines.

Ans- Properties of magnetic field lines:

They are closed and continuous curves. They are directed from the North Pole towards the South Pole outside the magnet. The tangent at any point on a field line gives the direction of magnetic field at that point. Two magnetic lines never intersect each other.

##### Que-11: Explain why iron filings which are sprinkled on a sheet of cardboard placed over a bar magnet take up a definite pattern when cardboard is slightly tapped.

Ans- The iron filings take up a definite pattern (curved lines). This happens because each piece of iron filing becomes a magnet to the magnetic induction of the magnet. It thus experiences a force in the direction of magnetic field of the bar magnet at that point and aligns itself along curved lines.

##### Que-12: Can two magnetic field lines intersect each other? Give reason to your answer.

Ans- No two magnetic field lines can intersect each other. If they do, there would be two directions of the field at that point which is not possible.

##### Que-13: In following figure, draw at least two magnetic field lines between the two magnets.

Ans- (a) The North Pole of two magnets is facing each other. So, the field lines will be

(b) The North Pole of one magnet is facing the South Pole of the other. So, the field lines will be

##### Que-14: State two evidences of the existence of earth’s magnetic field.

Ans- Two evidences of existence of earth’s magnetic field: (i) A freely suspended magnetic needle always rests in geographic north-south direction. (ii) Neutral points are obtained on plotting the field lines of a magnet.

Ans-

##### Que-16: What conclusion is drawn regarding the magnetic field at a point if a compass needle at that point rests in any direction? Give reason for your answer.

Ans- It can be concluded that magnetic field at that point is zero. This is because the earth’s magnetic field at that point is neutralized by the magnetic field of some other magnetized material.

##### Que-17: What is a neutral point? How is the position of neutral point located with the use of a compass needle?

Ans- Neutral points are the points where the magnetic field of the magnet is equal in magnitude to the earth’s horizontal magnetic field, but it is in opposite direction. Thus the net magnetic field at the neutral points is zero.

Since the net magnetic field is zero at neutral points, the compass needle remains unaffected (i.e. it comes to rest pointing in any direction) at these points and hence, they can be detected.

##### Que-18: State the positions of neutral points when a magnet is placed with its axis in the magnetic meridian and with its north pole (i) pointing towards the geographic north and (ii) pointing towards the geographic south.

Ans- (i) Neutral points will be in east-west direction.(ii) Neutral points will be north-south direction.

—  end of Magnetism Exe-10A Short Answer Concise Physics ICSE Class-9 Selina Publishers Solutions :—

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