# Magnetism Exe-10A Long Ans Concise Physics ICSE Class 9 Selina Publishers Solutions

## Magnetism Exe-10A Long Ans Concise Physics ICSE Class 9 Selina Publishers Solutions

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

### Induced Magnetism and Neutral Point

#### LONG ANSWER TYPE:

##### Question-1: (a) Draw the pattern of magnetic field lines near a bar magnet placed with its north pole pointing towards the geographic north.Indicate the position of neutral points by marking X.

(b) State whether the magnetic field lines in part (a) represent a uniform magnetic field or non- uniform magnetic field?

Answer-(a)=> The position of neutral points are as follows as the figure below.

(b)=> The magnetic field lines as shown in part (a) are non-uniform.

##### Question-2:

Fig.10.13

(a) Insert two magnetic field lines on either side of the magnet using arrow head to show the direction of each field line.

(b) Indicate by crosses, the likely positions of the neutral points.

(c) What is the magnitude of the magnetic field at each neutral point? Give a reason for your answer.

Answer- (a) The below figure (a) is as shown.

(b) The likely position of the neutral points are as shown in below figure (b).

(c) At neutral points, the magnitude of magnetic field is zero as at these points the magnetic field of the magnet is the same as the

magnitude of the earth’s horizontal magnetic field, but is the opposite in direction thereby cancelling each other.

##### Question-3: You are provided with two similar bars, one is a magnet and the other is a soft iron bar. How will you distinguish between them without the use of any other magnet or bar?

Answer-To distinguish between a magnet and soft iron bar, simply suspend both freely. A magnet will come to rest only in north-south direction whereas the soft iron bar will rest in any direction.

##### Question-4: A small magnet is suspended by a silk thread from a rigid support such that the magnet can freely swing. How will it rest ? Draw a diagram to show it.

Answer-When a magnet is suspended by a thread from a rigid support, and when it swings, it will rest in the geographic north-south direction, with the north pole being towards the geographic north, intending some angle with the horizontal as observed in the figure below.

##### Question-5:  Explain what do you understand by magnetic induction. What role does it play in attraction of a piece of iron by a magnet?

Answer- The process in which a piece of magnetic material acquires the magnetic properties temporarily in presence of another magnet near it is called the magnetic induction. When a piece of iron is placed near or in contact with a magnet, the piece of iron becomes a magnet i.e., it acquires the property of attracting iron filings when they are brought near its ends. Thus, a piece of iron behaves like a magnet as long as it is kept near (or in contact with) a magnet.

##### Question-6: Explain the mechanism of attraction of iron nails by a magnet when brought near them.

Answer- When iron nails are brought near one end of a magnet, the nearer end of iron piece acquires an opposite polarity by magnetic induction. Since unlike poles attract each other, therefore, iron nails are attracted towards the end of the magnet. Thus, the iron nail first becomes a magnet by induction and then it is attracted.

##### Question-7: A small iron bar is kept near the north pole of a bar magnet. How does the iron bar acquire magnetism? Draw a diagram to show the polarity on the iron bar. What will happen if the magnet is removed?

Answer-Due to the process of magnetic induction, the iron bar acquires magnetism.

The diagram above shows the polarity on the iron bar.The iron bar will lose its magnetism if the magnet is removed.

##### Question-8: Explain the method of plotting magnetic field lines by using a small compass needle.

Answer-The method explained below shows the plotting of magnetic field lines with the help of a small compass needle:    Procedure:

1. With the help of some board pins, fix a sheet of paper on a drawing board.

2. At point 1 as seen in the below figure, place a small compass needle. From the top of the needle, mark two pencil dots at exactly two ends of the needle.

3. Move the needle to the compass to point 2 so that one end of the needle coincides with the second pencil dot.

4. The process of moving the compass needle to points 3, 4, 5… is continued in order to get a few dots.

5. When various dots are joined, a straight line is obtained.

6. Hence, one line of magnetic field of earth is traced.

Starting from a different point, the process is repeated and another line of magnetic field is traced out. This way a few several lines of magnetic field can be traced out. Every line is required to be labelled with the help of an arrow from the south pole of the needle towards the north pole to represent the direction of the magnetic field. The figure below depicts several magnetic lines that are obtained this way.

—:  end of Magnetism Exe-10A Long Ans Concise Physics ICSE Class 9 Selina Publishers Solutions. : —

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