Selina solutions concise physics class 9 icse Solutions for Chapter 10 chapter 10 magnetism

Exercises in Chapter 10 chapter 10 magnetism Grade 9

Exercise 10A

Exercise 10B

Questions in Exercise 10A

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 magnetized when placed near a bar magnet by magnetic induction, while copper rod does not get magnetized]

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?

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

the bar will rest in any direction]

Fill in the blanks to complete the sentences:

(a) Two ends of a magnet are called ___________

(b) Unlike poles of a magnet _____________ each other

(c) Like poles of a magnet _____________ each other

(d) A freely suspended magnet rests in the geographic ___________ direction

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

Explain the term induced magnetism

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

Explain the mechanism of attraction of iron nails by a magnet when brought near them

Explain the following:

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

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

(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.

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

‘Induced magnetism is temporary’. Comment on this statement

‘Induction precedes attraction’. Explain the statement

What do you understand by the term magnetic field lines

State four properties of magnetic field lines

Explain why iron fillings which are sprinkled on a sheet of cardboard placed over a bar

magnet, take up a definite pattern when the cardboard is slightly tapped

Explain the method of plotting magnetic field lines by using a small compass needle

Can two magnetic field lines intersect each other? Give a reason for your answer

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

State two pieces of evidence of the existence of earth’s magnetic field

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

(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

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 material

nearby.

(a) Insert two magnetic field lines on either side of the magnet using arrowhead to show the

the direction of each field line.

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

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

The figuretabletopthe

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

What is a neural point? How is the position of a 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,

(ii) pointing towards the geographic south

Complete the following sentences:

(a) If the field lines in a magnetic field are parallel and equidistant, the magnetic field is

(b) At a neutral point, the resultant magnetic field is _____________

(c) The neutral points of a bar magnet kept with its north pole pointing towards geographic north are located ___________

Two like magnetic poles:

(a) Repel each other

(b) Attract each other

(c) First attract each other, then repel

(d) Neither attract nor repel

In a uniform magnetic field, the field lines are:

(a) Curved

(b) Parallel and equidistant straight lines

(c) Parallel, but non-equidistant straight lines

(d) Nothing can be said

Questions in Exercise 10B

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 the magnetic field of an 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.

(a) Draw a circuit diagram to represent the process.

(b) Label the poles of the electromagnet

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

(a) State the polarity at the end X and Y as the switch is pressed.

(b) Suggest one way of increasing the strength of the 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 the alternating current is 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:

(a) Steel

(b) Copper