# KSEEB SSLC Class 10 Science Solutions Chapter 13 Magnetic Effects of Electric Current

KSEEB SSLC Class 10 Science Solutions Chapter 13 Magnetic Effects of Electric Current are part of KSEEB SSLC Class 10 Science Solutions. Here we have given Karnataka SSLC Class 10 Science Solutions Chapter 13 Magnetic Effects of Electric Current.

## Karnataka SSLC Class 10 Science Solutions Chapter 13 Magnetic Effects of Electric Current

### KSEEB SSLC Class 10 Science Chapter 13 Intext Questions

Text Book Part I Page No. 118

Question 1.
Why does a compass needle get deflected when brought near a bar magnet?
A compass needle is a small bar magnet. When it is brought near a bar magnet, its magnetic field lines interact with that of the bar magnet. Hence, a compass needle shows a deflection.

Text Book Part I Page No. 122

Question 1.
Draw magnetic Held lines around a bar magnet. Field lines around a bar magnet

Question 2.
List the properties of magnetic lines of force.
The properties of magnetic lines of force are as follows:

(a) Magnetic field lines emerge from the north pole.
(b) They merge at the south pole.
(c) The direction of field lines inside the magnet is from the south pole to the north pole.
(d) Magnetic lines do not intersect with each other.

Question 3.
Why don’t two magnetic lines of force intersect each other?
If two field lines of a magnet intersect, then at the point of intersection, the compass needle points in two different directions. This is not possible. Hence. two field lines do not intersect each other.

Text Book Part I Page No. 123, 124

Question 1.
Consider a circular loop of wire lying in the plane of the table. Let the current pass through the loop clockwise. Apply the right- hand rule to find out the direction of the magnetic field inside and outside the loop. Since the current passes through the loop in a clockwise direction, therefore the front face of the loop will be the south pole and the back face, ie, the face touching the table will be north pole. According to right-hand rule, the direction of the magnetic field inside the loop will be pointing downward. Outside the loop, the direction of the magnetic field will be upward.

Question 2.
The magnetic field in a given region is uniform. Draw a diagram to represent it. The figure indicates that the magnetic field is the same at all points in the solenoid. That is field is uniform inside the solenoid.

Question 3.
Choose the correct option.
The magnetic field inside a long straight solenoid-carrying current
(a) is zero.
(b) decreases as we move towards its end.
(c) increases as we move towards its end.
(d) is the same at all points.
(d) is the same at all points.

Text Book Part I Page No. 125, 126

Question 1.

Which of the following property of a proton can change while it moves freely in a magnetic field? (There may be more than one correct answer.
(a) Mass
(b) Speed
(c) Velocity
(d) Momentum.
(c) and (d)
When a proton enters in a region of magnetic field, it experiences a magnetic force. As a result of the force, the path of the proton becomes circular. Hence, its velocity and momentum change.

Question 2.
In Activity 13.7 of NCERT Book, how do we think the displacement of rod AB will be affected if (i) current in rod AB is increased; (ii) a stronger horse-shoe magnet is used; and (iii) length of the rod AB is increased?
A current-carrying conductor placed in a magnetic field experiences a force. The magnitude of force increases with the amount of current, strength of the magnetic field, and the length of the conductor.

Hence, the magnetic force exerted on rod AB and its deflection will increase if, ’

1. current in rod AB is increased
2. a stronger horse-shoe magnet is used
3. length of rod AB is increased.

Question 3.
A positively – charged particle (alpha-particle) projected towards west is deflected towards north by a magnetic field. The direction of magnetic field is,
(a) towards south
(b) towards east
(c) downward
(d) upward
(d) The direction of the magnetic field can be determined by the Fleming’s left hand rule. According this rule, if we arrange the thumb, the center finger, and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the center finger gives the direction of current, and the forefinger points in the direction of magnetic field. Since the direction of positively charged alpha particle is towards west, the direction of current will be the same i.e., towards west. Again, the direction of magnetic force is towards north. Hence, according to Fleming’s left hand rule, the direction of magnetic field will be upwards.

Text Book Part I Page No 127

Question 1.
State Fleming’s left-hand rule.
Fleming’s left hand rule states that if we arrange the thumb, the center finger and the forefinger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the center finger gives the direction of current and the forefinger points in the direction of magnetic field.

Question 2.
What is the principle of an electric motor?
The working principle of an electric motor is based on the magnetic effect of current. A current-carrying loop experiences a force and rotates when placed in a magnetic field. The direction of rotation of the loop is given by the Fleming’s left-hand rule.

Question 3.
What is the role of the split ring in an electric motor?
The split ring in the electric motor acts as a commutator. The commutator reverses the direction of current flowing through the coil after each half rotation of the coil. Due to this reversal of the current, the coil continues to rotate in the same direction.

Text Book Part I Page No. 130

Question 1.
Explain different ways to induce current in a coil.
We can induce current in a coil either by moving it in a magnetic field or by changing the magnetic around it. It is convenient in most situations to move the coil in a magnetic field.

Text Book Part I Page No. 131

Question 1.
State the principle of an electric generator.
Based on the phenomenon of electromagnetic induction, electric generator are prepared. In an electric generator, Mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. This is the principle of an electric generator.

Question 2.
Name some sources of direct current.
Dry cell, Battery and D.C. generator.

Question 3.
Which sources produce alternating current?
A.C. generator and D.C. generator.

Question 4.
Choose the correct option. A rectangular coil of copper wires is rotated in a magnetic field. The direction of the induced current changes once in each
(a) two revolutions
(b) one revolution
(c) half revolution
(d) one-fourth revolution.
(c) half revolution.

Text Book Part I Page No. 132

Question 1.
Name two safety measures commonly used in electric circuits and appliances.
Two safety measures commonly used in electric circuits and appliances are as follows:
(i) Each circuit must be connected with an electric fuse. This prevents the flow of excessive current through the circuit. When the current ‘passing through the wire exceeds the maximum limit of the fuse element, the fuse melts to stop the flow of current through that circuit, hence protecting the appliances connected to the circuit

(ii) Earthing is a must to prevent electric shocks. Any leakage of current in an electric appliance is transferred to the ground and people using the appliance do not get the shock.

Question 2.
An electric oven of 2 kW power rating is operated in a domestic electric circuit (220V) that has a current rating of 5 A. What result do you expect? Explain.
Current drawn by the electric oven can be obtained by the expression,
P = VI
Where, I = $$\frac { P }{ V }$$
Power of the oven, P = 2k W = 2000 W
Voltage supplied, V = 220 v
I = $$\frac { 2000 }{ 220 }$$ = 9.09 A
Hence, the current drawn by the electric oven is 9.09 A, which exceeds the safe limit of the circuit. Fuse element of the electric fuse will melt and break the circuit.

Question 3.
What precautions should be taken to avoid the overloading of domestic electric circuits?
The precautions that should be taken to avoid the overloading of domestic circuits are as follows:

(a) Too many appliances should not be connected to a single socket.
(b) Too many appliances should not be used at the same time.
(c) Faulty appliances should not be connected in the circuit.
(d) Fuse should be connected in the circuit.

### KSEEB SSLC Class 10 Science Chapter 13 Textbook Exercises

Question 1.
Which of the following correctly describes the magnetic Held near a long straight wire?
(a) The field consists of straight lines perpendicular to the wire.
(b) The field consists of straight lines parallel to the wire.
(c) The field consists of radial lines originating from the wire.
(d) The field consists of concentric circles centred on the wire.
(d) The field consists of concentric circles centred on the wire.

Question 2.
The phenomenon of electro-magnetic induction is
(a) the process of charging a body.
(b) the process of generating magnetic field due to a current passing through a coil.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.
(d) the process of rotating a coil of an electric motor.
(c) producing induced current in a coil due to relative motion between a magnet and the coil.

Question 3.
The device used for producing electric current is called a
(a) generator
(b) galvanometer
(c) ammeter
(d) motor
(a) An electric generator produces electric current. It converts mechanical energy into electricity.

Question 4.
The essential difference between an AC generator and a DC generator is that
(a) AC generator has an electromagnet while a DC generator has permanent magnet.
(b) DC generator will generate a higher voltage.
(c) AC generator will generate a higher voltage.
(d) AC generator has slip rings while the DC generator has a commutator.
(d) An AC generator has two rings called slip rings. A DC generator has two half rings called commutator. This is the main difference between both the types of generators.

Question 5.
At the time of short circuit, the current in the circuit
(a) reduces substantially
(b) does not change.
(c) increases heavily.
(d) vary continuously.
(c) When two naked wires of an electric circuit touch each other, the amount of current that is flowing in the circuit increases abruptly. This causes short-circuit.

Question 6.
State whether the following statements are true or false.
(a) An electric motor converts mechanical energy into electrical energy
(b) An electric generator works on the principle of electromagnetic induction.
(c) The field at the center of a long circular coil carrying current will be parallel straight lines.
(d) A wire with a green insulation is usually the live wire of an electric supply.
(a) False
An electric motor converts electrical energy into mechanical energy.

(b) True
A generator is an electric device that generates electricity by rotating a coil in a magnetic field. It works on the principle of electromagnetic induction.

(c) True
A long circular coil is a long solenoid. The magnetic field lines inside the solenoid are parallel lines.

(d) False
Live wire has red insulation cover, whereas earth wire has green insulation colour in the domestic circuits.

Question 7.
List two methods of producing magnetic fields.
Two methods of producing magnetic fields:

1. Permanent magnets
2. Electromagnets

Question 8.
How does a solenoid behave like a magnet? Can you determine the north and south poles of a current-carrying solenoid with the help of a bar magnet? Explain.  One end of the solenoid behaves as a magnetic north pole, while the other behaves as the south pole. The field lines inside the solenoid are in the form of parallel straight lines. This indicates that the magnetic field is the same at the points inside the solenoid.

As shown in figure a strong magnetic field produced inside a solenoid can be used to magnetise a piece of Magnetic material, like soft iron, when placed inside the coil. The magnet so formed is called an electromagnet.

Question 9.
When is the force experienced by a current-carrying conductor placed in a magnetic field largest?
If the direction of magnetic field and flow of electric current are mutually perpendicular then force experienced by a current-carrying conductor in a magnetic field is largest.

Question 10.
Imagine that you are sitting in a chamber with your back to one wall. An electron beam, moving horizontally from back wall towards the front wall, is deflected by a strong magnetic field to your right side. What is the direction of magnetic field?
The direction of magnetic field is given by Fleming’s left hand rule. Magnetic field inside the chamber will be perpendicular to the direction of current (opposite to the direction of electron) and direction of deflection\force i.e., either upward or downward. The direction of current is from the front wall to the back wall because negatively charged electrons are moving from back wall to the front wall The direction of magnetic force is rightward. Hence, using Fleming’s left hand rule, it can be concluded that the direction of magnetic field inside the chamber is downward.

Question 11.
Draw a labelled diagram of an electric motor. Explain its principle and working. What is the function of a split ring in an electric motor? Principle:
An electric motor is a rotating device that converts electrical energy to mechanical energy working.

Working:
Current in the coil ABCD enters from the source battery through conducting brush X and flow back to the battery through brush Y. Notice that the current in the Arm AB of the coil flows from A to B. In arm CD it flows from C to D that is opposite to the direction of current through arm AB on applying Fleming’s left hand rule for the direction of force on a current¬carrying conductor in a magnetic field. We find that the force acting on arm AB pushes it downwards while the force acting on arm CD pushes it upwards.

Thus the coil and the Axle O, mounted free to turn about an axis, rotate anti-clockwise at half rotation. Q makes contact with the brush X and P with brush Y. Therefore the current in the coil gets reversed and flows along the path DCBA. The reversal of current also reverses the direction of force acting on the two arms AB and CD. Thus the arm AB of the coil that was earlier pushed down, is now pushed up and the arm CD previously pushed up is pushed down. There is a continuous rotation of the coil and to the axle.
Split rings in electric motors acts as a commutator.

Question 12.
Name some devices in which electric motors are used.
Some devices in which electric motors are used as follows:

(a) Water pumps
(b) Electric fans
(c) Electric mixers
(d) Washing machines

Question 13.
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is
(i) pushed into the coil
(ii) withdrawn from inside the coil
(iii) held stationary inside the coil?
A current induces in a solenoid if a bar magnet is moved relative to it. This is the principle to electromagnetic induction.
(i) When the bar magnet is pushed into a coil of insulated copper wire, a current is induced momentarily in the coil. As a result, the needle of the galvanometer deflects momentarily in a particular direction.

(ii) When the bar magnet is withdrawn from inside the coil of. the insulated copper wire, a current is again induced momentarily in the coil in the opposite direction. As a result, the needle of the galvanometer deflects momentarily in the opposite direction.

(iii) When a bar magnet is held stationary inside the coil, no current will be induced in the coil. Hence, galvanometer will show no deflection.

Question 14.
Two circular coils A and B are placed close to each other. If the current in the coil A is changed, will some current be induced in the coil B? Give reason.
Two circular coils A and B are placed close to each other. When the current in coil A is changed, the magnetic field associated with it also changes. As a result, the magnetic field around coil B also changes. This change in magnetic field lines associated coil B also changes. This change in magnetic field lines around coil B induces an electric current in it. This is called electromagnetic induction.

Question 15.
State the rule to determine the direction of a

1. magnetic field produced around 0 straight conductor-carrying current
2. force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and
3. current induced in a coil due to its rotation in a magnetic field.

1. Maxwell’s right hand thumb rule.
2. Fleming’s left hand rale.
3. Fleming’s right hand rule.

Question 16.
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of the brushes? Principle: In an electric generator, mechanical energy is used to rotate a conductor in a magnetic field to produce electricity. It is working on the principle of electromagnetic induction.

Working: When the Axle attached to the two rings is rotated such that the arm AB moves up (and the arm CD moves down) in the magnetic field produced by the permanent magnet. Let us say the coil ABCD is rotated clockwise in the arrangement. By applying Fleming’s right-hand rule, the induced currents are set up in these arms along with the directions AB and CD. Thus an induced current flows in the direction ABCD. If there are a larger number of turns in the coil, the current generated in each turn adds up to give a large current through the coil. This means that the current in the external circuit flows from B2 and B1.

After half a rotation, arm CD starts moving up and AB moving down. As a result, the directions of the induced currents in both the arms change, giving rise to the net induced current in the direction DCBA. The current in the external circuit now flows from B1 to B2. Thus after every half rotation the polarity of the current in the respective arms changes.

There are two brushes and in the electric generator, one brush is at all times in contact with the arm moving up in the field, while the other is in contact with the arm moving down. Because of these Brushes unidirectional current is produced.

Question 17.
When does an electric short circuit occur?
Overloading can occur when the live wire and the neutral wire come into direct current (This occurs when the insulation of wires is damaged or there is a fault in the appliance) In such a situation, the current in the circuit abruptly increases. This is called short-circuiting.

Question 18.
What is the function of an earth wire? Why is it necessary to earth metallic appliances?
This is used as a safety measure, especially for those appliances that have a metallic body, for example, electric press, toaster, table fan, refrigerator, etc. The metallic body is connected to the earth wire which provides a low-resistance conducting path for the current. Thus earth wire ensures that any leakage of current to the metallic body of the appliance keeps its potential to that of the earth and the user may not get a severe electric shock.

### KSEEB SSLC Class 10 Science Chapter 13 Additional Questions and Answers

1. Fill in the blanks:

Question 1.
Magnetic field is a quantity that has both …….. and ……
Magnitude, direction.

Question 2.
An electric current through a metallic conductor produces a ……. around it.
Magnetic field.

Question 3.
In electric motors, the …… acts as a commutator