Selina solutions for Concise Physics [English] Class 9 ICSE chapter 10 - Magnetism [Latest edition]

What is a lodestone? 

What is a natural magnet? State two limitations of a natural magnet. 

What is an artificial magnet? State two reasons why do we need artificial magnets .

How will you test whether a given rod is made of iron or copper?

[Hint : Iron rod gets magnetised when placed near a bar magnet by magnetic induction, while copper rod does not get magnetised]

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

[Hint : A magnet when suspended freely will rest only in the north-south direction, but the soft iron bar will rest in any direction]

Fill in the blank to complete the sentence :

The two ends of a magnet are called __________.

Fill in the blank to complete the sentence :

Unlike poles of a magnet ___________ each other.

Fill in the blank to complete the sentence :

Like poles of a magnet ______________ each other.

Fill in the blank to complete the sentence :

A freely suspended magnet rests in the geographic ___________ direction.

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.

Explain what you understand by magnetic induction. What role does it play in attraction of a piece of iron by a magnet?

Explain the following :

When two pins are hung by their heads from the same pole of a magnet, their pointed ends moves apart.

Explain the following :

Several soft iron pins can cling, one below the other, from the pole of a magnet.

Explain the following :

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.

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?

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.

Can two magnetic field lines intersect each other? Give reason to your answer.

In following figure, draw at least two magnetic field lines between the two magnets.

(a)

In following figure, draw at least two magnetic field lines between the two magnets.

(b)

Sketch four magnetic field lines as obtained in a limited space on a horizontal plane in the earth's magnetic field alone.

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.

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

Figure. shows a bar magnet placed on the table top with its north pole pointing towards south. The arrow shows the north-south direction. There are no other magnets or magnetic materials nearby.

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

Figure. shows a bar magnet placed on the table top with its north pole pointing towards south. The arrow shows the north-south direction. There are no other magnets or magnetic materials nearby.

Indicate by crosses, the likely positions of the neutral points.

Figure. shows a bar magnet placed on the table top with its north pole pointing towards south. The arrow shows the north-south direction. There are no other magnets or magnetic materials nearby.

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

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.

What is a neutral point? How is the position of neutral point located with the use of a compass needle?

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.

Complete the following sentence :

If the field lines in a magnetic field are parallel and equidistant, the magnetic field is __________  .

Complete the following sentence :

At a neutral point, the resultant magnetic field is ___________.

Complete the following sentence :

The neutral points of a bar magnet kept with its north pole pointing towards geographic north are located ____________.

Two like magnetic poles:

In a uniform magnetic field, the field lines are:

What is an electromagnet?

Name the material used for preparing an electromagnet.

How is an electromagnet made? Name two factors on which the strength of magnetic field of the electromagnet depends.

You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper wire and a switch.

1. Draw a circuit diagram to represent the process.
2. Label the poles of the electromagnet.

The following figure shows a coil wound around a soft iron bar XY.

1. State the polarity at the ends X and Y as the switch is pressed.
2. Suggest one way of increasing the strength of electromagnet so formed.

A coil of insulated copper wire is wound around a piece of soft iron and current is passed in the coil from a battery. What name is given to the device so obtained? Give one use of the device mentioned by you.

Show with the aid of a diagram how a wire is wound on a U-shaped piece of soft iron in order to make it an electromagnet. Complete the circuit diagram and label the poles of the electromagnet.

State two ways through which the strength of an electromagnet can be increased. 

Name one device that uses an electromagnet.

State two advantages of an electromagnet over a permanent magnet.

State two differences between an electromagnet and a permanent magnet.

Why is soft iron used as the core of the electromagnet in an electric bell?

How is the working of an electric bell affected, if alternating current be used instead of direct current? 

Name the material used for making the armature of an electric bell. Give a reason for your answer. 

Electromagnets are made up of :

The strength of the electromagnet can be increased by