Electro-Magnetism ICSE Class-10 Concise Physics Selina Solutions Chapter-10. We Provide Step by Step Answer of Exercise-10(A), MCQs-10(A), Exercise-10(B), MCQ-10(B), Exercise-10(C), MCQ-10(C) and Numericals -10(C) . Questions of Exercise-10 Electro-Magnetism ICSE Class-10 Concise Class-10 . Visit official Website CISCE for detail information about ICSE Board Class-10.
| Board | ICSE |
| Publications | Selina Publication |
| Subject | Physics |
| Class | 10th |
| Chapter-10 | Electro-Magnetism (Exercise-10A and 10B) |
| Book Name | Concise |
| Topics | Solution of Exercise-10(A), MCQs-10(A), Exercise-10(B), MCQ-10(B), Exercise-10(C), MCQ-10(C) and Numericals -10(C) |
| Academic Session | 2021-2022 |
Electro-Magnetism ICSE Class-10 Concise Physics Selina Solutions Chapter-10
-: Select Exercise :-
Exercise-10(A), MCQs-10(A), Exercise-10(B), MCQ-10(B),
Exercise-10(C), MCQ-10(C) and Numericals -10(C)
Note:- Read the chapter Electro-Magnetism carefully and then solve All the example given in your text book before starting Solution of Chapter – 10 Electro-Magnetism exercise. Do not forget using keyword in your answer in exam of council.
Exercise – 10 (A) Electro-Magnetism ICSE Class-10 Concise Physics Selina
Page 239
Question 1
By using a compass needle describe how can you demonstrate that there is a magnetic field around a current carrying conductor.
Answer 1
Experiment:
In Fig , AB is a wire lying in the north- south direction and connected to a battery through a rheostat and a tapping key. A compass needle is placed just below the wire. It is observed that
(1)When the key is open i.e., no current passes through the wire, the needle shows no deflection and it points in the N-S direction (i.e. along the earth’s magnetic field). In this position, the needle is parallel to the wire as shown in Fig. (a).
(2)When the key is pressed, a current passes in the wire in the direction from A to B (i.e. From
south to north) and the north pole(N) of the needle deflects towards the west [Fig. (b)].
(3)When the direction of current in the wire is reversed by reversing the connections at the
terminals of the battery, North Pole (N) of the needle deflects towards the east [Fig. (c)].
(4)If the compass needle is placed just above the wire, the North Pole (N) deflects towards
east when the direction of current in wire is from A to B [Fig. (d)], but the needle deflects
towards west as in fig (e), if the direction of current in wire is from B to A.
The above observations of the experiment suggest that a current carrying wire produces a
magnetic field around it.
By using a compass needle describe how can you demonstrate that there is a magnetic field around a current carrying conductor.
Question 2
Draw a diagram showing the direction of three magnetic field lines due to a straight wire carrying current. Also show the direction of current in the wire.
Answer 2
Question 3
How is magnetic field due to a straight current carrying wire affected if current in wire is (a) decreased, (b) reversed?
Answer 3
(a) On decreasing the current the magnetic field lines become rarer.
(b) The direction of magnetic field lines will get reversed.
Question 4
State a law, which determines the direction of magnetic field around a current carrying wire.
Answer 4
Right hand thumb rule determines the direction of magnetic field around a current carrying wire.
It states that if we hold the current carrying conductor in right hand such that the thumb points in the direction of flow of current, then the fingers encircle the wire in the direction of the magnetic fields lines.
Question 5
A straight wire lying in a horizontal plane carries a current from north to south.
(a) What will be the direction of magnetic field at a point just underneath it?
(b) Name the law used to arrive at this answer in part (a).
Answer 5
(a) The direction of magnetic field at a point just underneath is towards east.
(b) Right hand thumb rule.
Question 6
What will happen to a compass needle when the compass is placed below a wire and a current is made to flow through the wire? Give reasons to justify your answer.
Answer 6
A current carrying conductor produces a magnetic field around it and the magnetic needle in this magnetic field experience a torque due to which it deflects to align itself in the direction of magnetic field.
Question 7
Draw a labelled diagram showing the three magnetic field lines of a loop carrying current. Mark the direction of current and the direction of magnetic field by arrows in your diagram.
Answer 7
Page 240
Question 8
A wire, bent into a circle, carries current in an anticlockwise direction. What polarity does this face of the coil exhibit?
Answer 8
Face of the coil exhibit North polarity.
Question 9
What is the direction of magnetic field at the centre of coil carrying current in (i) clockwise, (ii) anticlockwise direction?
Answer 9
(i) Along the axis of coil inwards.
(ii) Along the axis of coil outwards.
Question 10
Draw a diagram to represent the magnetic field lines along the axis of a current carrying solenoid. Mark arrows to show the direction of current in the solenoid and the direction of magnetic field lines.
Answer 10
Question 11
Name and state the rule by which the polarity at the ends of a current carrying solenoid is determined.
Answer 11
Right hand thumb rule: If we hold the current carrying conductor in right hand such that the thumb points in the direction of flow of current, then the fingers encircle the wire in the direction of the magnetic fields lines.
Question 12
The diagram in. Fig 10.17 shows a small magnet placed near a solenoid AB. Current is switched on in the solenoid by pressing the key K. (a) State the polarity at the ends A and B. (b) Will the magnet be attracted or repelled? Give a reason for your answer.
Answer 12
(a) A – North pole, B – South pole.
(b) The magnet will be repelled because the end of the solenoid near the north pole of magnet becomes the north pole as current at this face is anticlockwise and the two like poles repel.
Question 13
The following diagram shows a spiral coil wound on a hollow cardboard tube AB. A magnetic compass is placed close to it. Current flows by closing the key. (a) What will be the polarity at the ends A and B? (b) How will the compass needle be affected? Give reason.
Answer 13
(a) A – North pole, B – South pole.
(b) The north pole of compass needle will deflect towards west.
Reason: The end A of the coil behaves like north pole which repels north pole of compass needle towards west.
Question 14
State two ways by which the magnetic field due to a solenoid can be made stronger.
Answer 14
The magnetic field due to a solenoid can be made stronger by using:
(i) By increasing the number of turns of winding in the solenoid.
(ii) By increasing the current through the solenoid.
Question 15
Why does a current carrying freely suspended solenoid rest along a particular direction? State the direction in which it rests.
Answer 15
A current carrying freely suspended solenoid at rest behaves like a bar magnet. It is because a current carrying solenoid behaves like a bar magnet. It align itself in north south direction.
Question 16
What effect will there be on a magnetic compass when it is brought near a current carrying solenoid?
Answer 16
The needle of the compass will rest in in the direction of magnetic field due to solenoid at that point.
Question 17
How is the magnetic field due to a solenoid carrying current affected if a soft iron bar is introduced inside the solenoid?
Answer 17
Magnetic field due to a solenoid carrying current increases if a soft iron bar is introduced inside the solenoid.
Question 18
Complete the following sentences:
(a)When current flows in a wire, it creates ________.
(b) On reserving the direction of current in a wire, the magnetic field produced by it gets _____.
(C)A current carrying solenoid behaves like a _________.
(D)A current carrying solenoid when freely suspended, it always rest in __________ direction.
Answer 18
(A)When current flows in a wire, it creates magnetic field around it.
(B) On reserving the direction of current in a wire, the magnetic field produced by it gets reversed.
(C)A current carrying solenoid behaves like a bar magnet
(D)A current carrying solenoid when freely suspended, it always rest in north-south direction.
Question 19
You are required to make an electromagnet from a soft iron bar by using a cell, an insulated coil of copper and a switch. (a) Draw a circuit diagram to represent the process. (b) Label the poles of the electromagnet.
Answer 19
Question 20
The fig 10.19 in 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 electromagnet so formed.
Answer 20
(a)X-north pole, Y –south pole.
(b)By reducing resistance of circuit by mean of rheostat to increase current.
Page 241
Question 21
(a) What name is given to a cylindrical coil of diameter less than its length?
(b) If a piece of soft iron is placed inside the coil mentioned in part (a) and current is passed in the coil from a battery, what name is then given to the device so obtained?
(c) Give one use of the device mentioned in part (b).
Answer 21
(a) Solenoid is a cylindrical coil of diameter less than its length.
(b) The device so obtained is electromagnet.
(c) It is used in electric relay.
Question 22
Show with the aid of the 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.
Answer 22
Question 23
What is an electromagnet? Name two factors on which the strength of magnetic field of an electromagnet depends and state how does it depend on the factors stated by you.
Answer 23
An electromagnet is a temporary strong magnet made from a piece of soft iron when current flows in the coil wound around it. It is an artificial magnet.
The strength of magnetic field of an electromagnet depends on:
(i) Number of turns: The strength of magnetic increases on increasing the number of turns of winding in the solenoid.
(ii) Current: The strength of magnetic field increases on increasing the current through the solenoid.
Question 24
Figure shows the current flowing in the coil of wire wound around the soft iron horse shoe core. (a) State the polarities developed at the ends A and B.
(b) How will the polarity at the ends A and B change on reversing the direction of current.
(c) Suggest one way increase the strength of magnetic filed produce.
Answer 24
(a)At A-south pole and at B-north pole.
(b)Polarity will also reverse. A will become north pole and B will become south pole.
(c)By increasing the number of turns
Question 25
State two ways through which the strength of an electromagnet can be increased.
Answer 25
the strength of an electromagnet can be increased by following ways:
(i) By increasing the number of turns of winding in the solenoid.
(ii) By increasing the current through the solenoid.
Question 26
Name one device that uses an electromagnet.
Answer 26
Electric bell
Question 27
State two advantages of an electromagnet over a permanent magnet.
Answer 27
1.An electromagnet can produce a strong magnetic field.
2.The strength of the magnetic field of an electromagnet can easily be changed by changing the current in its solenoid.
Question 28
State two differences between an electromagnet and a permanent magnet.
Answer 28
differences between an electromagnet and a permanent magnet
| Electromagnet | Permanent magnet |
| It is made up of soft iron | It is made up of steel. |
| The magnetic field strength can be changed. | The magnetic field strength cannot be changed. |
| The electromagnets of very strong field can be made. | The permanent magnets are not so strong. |
Question 29
Why is soft iron used as the core of the electromagnet in an electric bell?
Answer 29
The soft iron bar acquires the magnetic properties only when an electric current flows through the solenoid and loses the magnetic properties as the current is switched off. That’s why soft iron is used as the core of the electromagnet in an electric bell.
Question 30
How is the working of an electric bell affected, if alternating current be used instead of direct current?
Answer 30
If an a.c. source is used in place of battery, the core of electromagnet will get magnetized, but the polarity at its ends will change. Since attraction of armature does not depend on the polarity of electromagnet, so the bell will still ring on pressing the switch.
Question 31
The incomplete diagram of an electric bell is given in figure. Draw winding of coil on the core and complete the electric circuit in the diagram
Answer 31
Question 32
Name the material used for making the armature of an electric bell. Give a reason for your answer.
Answer 32
The material used for making the armature of an electric bell is soft iron which can induce magnetism rapidly.
Selina Physics Solution “Electro-Magnetism” Exercise 10 (A) – Multiple Choice Type :
Page 241
Question 1
The presence of magnetic field at a point can be detected by :
(a) A strong magnet
(b) A solenoid
(c) A compass needle
(d) A current carrying wire
Answer 1
The presence of magnetic field at a point can be detected by a compass needle.
Note: In the presence of a magnetic field, the needle of compass rests only in the direction of magnetic field and in the absence of any magnetic field, the needle of compass can rest in any direction. In the earth’s magnetic field alone, the needle rests along north-south direction.
Question 2
On reversing the direction of current in a wire, the magnetic field produced by it:
(a) Gets reversed in direction
(b) Increases in strength
(c) Decreases in strength
(d) Remains unchanged in strength and direction
Answer 2
By reversing the direction of current in a wire, the magnetic field produced by it gets reversed in direction.
Hint: On reversing the direction of current in a wire, the polarity of the faces of the wire also reverses. Thus, the direction of magnetic field produced by it also gets reversed.
Selina Physics Solution Electro-Magnetism For Class 10th
Exercise 10 – (B)
Page 246
Question 1
Name three factors on which the magnitude of force on a current carrying conductor placed in a magnetic field depends and state how does the force depend on the factors stated by you.
Answer 1
The magnitude of force on a current carrying conductor placed in a magnetic field depends on:
(i) On strength of magnetic field B.
(ii) On current I in the conductor.
(iii) On length of conductor.
Magnitude of force on a current carrying conductor placed in a magnetic field depends directly on these three factors.
Question 2
State condition when magnitude of force on a current carrying conductor placed in a magnetic field is (a) zero,(b) maximum
Answer 2
(a)When current in the conductor is in the direction of magnetic field force will be zero.
(b) When current in the conductor is normal to the magnetic field.
Question 3
How will the direction of force be changed, if the current is reversed in the conductor placed in a magnetic field?
Answer 3
Direction of force is also reversed.
Question 4
Name and state the law which is used to determine the direction of force on a current carrying conductor placed in a magnetic field.
Answer 4
Fleming’s left hand rule: Stretch the forefinger, middle finger and the thumb of your left hand mutually perpendicular to each other. If the forefinger indicates the direction of magnetic field and the middle finger indicates the direction of current, then the thumb will indicate the direction of motion of conductor.
Question 5
State Fleming’s left handle rule.
Answer 5
Fleming’s left hand rule: Stretch the forefinger, middle finger and the thumb of your left hand mutually perpendicular to each other. If the forefinger indicates the direction of magnetic field and the middle finger indicates the direction of current, then the thumb will indicate the direction of motion of conductor.
Question 6
State the unit of magnetic field in terms of the force experienced by a current carrying conductor placed in a magnetic field.
Answer 6
Unit is: Newton/ampere x meter (or NA-1m-1).
Question 7
A flat coil ABCD is freely suspended between the pole pieces of a U-shaped permanent magnet with the plane of coil parallel to the magnetic field.
(a)What happens when a current is passed in the coil?
(b) When will coil come to rest?
(c) When will the couple acting on the coil be (i) maximum, (ii) minimum?
(d) Name an instrument which makes use of the principle stated above.
Answer 7
(a)The coil will experience a torque due to which it will rotate.
(b) The coil will come to rest when their plane become normal to the magnetic field.
(c) (i) When plane of a oil is parallel to the magnetic field,
(ii) When plane of coil is normal to the magnetic field.
(d) The instrument which makes use of the principle stated above is d.c. motor.
Question 8
A coil ABCD mounted on an axle is placed between the poles N and S of a permanent magnet.
(a) In which direction will the coil begin to rotate when current is passed through the coil in direction ABCD by connecting a battery at the ends A and D of the coil?
(b)Why is a commutator necessary for continuous rotation of coil?
(c) Complete the diagram with commutator, etc. for the flow of current in the coil.
Answer 8
(a)The coil begins to rotate in anticlockwise direction.
(b) This is because, after half rotation, the arms AB and CD get interchanged, so the direction of torque on coil reverses. To keep the coil rotating in same direction, commutator is needed to change the direction of current in the coil after each half rotation of coil.
Page 247
Question 9
What is an electric motor? State its principle.
Answer 9
Electric motor: An electric motor is a device which converts the electrical energy into the mechanical energy.
Principle: An electric motor (dc motor) works on the principle that when an electric current is passed through a conductor placed normally in a magnetic field, a force acts on the conductor as a result of which the conductor begins to move and mechanical energy is obtained.
Question 10
Draw a labelled diagram of a d.c motor showing its main parts.
Answer 10
Question 11
What energy conversion does take place during the working of a d.c motor?
Answer 11
Electrical energy converts into mechanical energy.
Question 12
State two ways by which the speed of rotation of an electric motor can be increased.
Answer 12
The speed of rotation of an electric motor can be increased by:
(i)Increasing the strength of current.
(ii)Increasing the number of turns in the coil.
Question 13
Name two appliances in which an electric motor is used.
Answer 13
Electric motor is used in electrical gadgets like fan, washing machine, juicer, mixer, grinder etc.
Selina Physics Solution Electro-Magnetism For Class 10th
Exercise 10 – (B) Multiple Choice Type
Page 247
Question 1
In an electric motor, the energy transformation is:
(a) From electrical to chemical
(b) From chemical to light
(c) From mechanical to electrical
(d) From electrical to mechanical
Answer 1
In an electric motor, the energy transformation is from electrical to mechanical.
Note: An electric motor is a device which converts electrical energy into mechanical energy.
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