# NCERT Solutions Class 10 for Science Chapter 13 Magnetic Effect of Electric Current

NCERT Solutions Class 10 for Science Chapter 13 Magnetic Effect of Electric Current : In this post, we will share with you all the detailed NCERT Solutions of Class 10 Science Chapter 13 Magnetic Effect of Electric Current. This will contain both in-text and back-exercise questions for Science and Social Science, and all exercise questions for Mathematics. For all school and board level examinations, doing all the NCERT Questions is a must.

# Why are NCERT Questions Important?

NCERT Questions and Answers not only help you get hold of concepts firmly and enhance your understanding, but also form the base of all types of questions asked in exams. Questions asked in exam are more or less the same type as mentioned in NCERT. Moreover, sometimes the questions in NCERT are directly asked in exams, as it is, without any changes.

Hence, it’s very important to understand NCERT Questions and Answers.

# Class 10 Science Chapter 13 Magnetic Effect of Electric Current

## In-Text Questions (Page 224)

Question 1:
Why does a compass needle get deflected when brought near a bar magnet ?

The magnetic field of the magnet exerts force on both the poles of the compass needle. The forces experienced by the two poles are equal and opposite. These two forces form a couple which deflects the compass needle.

## In-Text Questions (Page 228)

Question 1:
Draw magnetic field lines around a bar magnet.

Question 2:
List the properties of magnetic lines of force.

Properties of magnetic lines of force :

1.The magnetic field lines originate from the north pole of a magnet and end at its south pole.
2.The magnetic field lines become closer to each other near the poles of a magnet but they are widely separated at other places.
3.Two magnetic field lines do not intersect one another.

Question 3:
Why don’t two magnetic lines of force intersect each other ?

If two magnetic field lines intersect then at the point of intersection the compass needle shows two different directions, which is not possible, hence they do not intersect with each other.

## In-Text Questions (Page 229)

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.

As shown in figure alongside, each section of wire produces its concentric set of lines of force. By applying right hand thumb rule, we find that all the sections produce magnetic field downwards at all points inside the loop while at the outside points, the field is directed upwards. Therefore, the magnetic field acts normally into the plane of the paper at the points inside the loop and normally out of the plane of paper at points outside the loop

Question 2:
The magnetic field in a given region is uniform. Draw a diagram to represent it.

A uniform magnetic field in a region is represented by drawing parallel straight lines, ail pointing in the same direction.

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

d. is the same at all points
The magnetic field inside a long straight current carrying solenoid is uniform therefore it is the same at all points.

## In-Text Questions (Page 231-232)

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.)
(i) Mass
(ii) Speed
(iii) Velocity
(iv) Momentum

(c) and (d)
When a proton enters the region of magnetic field, it experiences magnetic force. Due to which the path of the proton becomes circular. As a result, the velocity and the momentum change.

Question 2:
In Activity 13.7, 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 when placed in a magnetic field experiences force. The magnitude of this force will increase with the increase in the amount of current, length of conductor and the strength of the magnetic field. Hence, the strength of the magnetic force exerted on the rod AB and its displacement will increase if

1.The current in rod AB is increased
2.Stronger horse shoe magnet is used
3.When the length of the rod AB increases

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 :
(i) towards south
(ii) towards east
(iii) downward
(iv) upward

The direction of the magnetic field can be determined using the Fleming’s Left hand rule. According to the rule, if we arrange our thumb, forefinger and the middle finger of the left hand right perpendicular to each other, then the thumb points towards the direction of the magnetic force, the middle finger the direction of current and the forefinger the direction of magnetic field. Since the direction of positively charged particle is towards west, the direction of the current will also be towards the west. The direction of the magnetic force is towards the north, hence the direction of magnetic field will be upward according to Fleming’s Left hand rule.

## In-Text Questions (Page 233)

Question 1:
State Fleming’s left-hand rule.

Fleming’s Left hand rule states that if we arrange our thumb, forefinger and middle finger of the left hand at right angles to each other, then the thumb points towards the direction of the magnetic force, the forefinger points towards the direction of magnetic field and the middle finger points towards the direction of current.

Question 2:
What is the principle of an electric motor?

The working principle of electric motor is based on the magnetic effect of current. A current carrying conductor when placed in a magnetic field experiences force and rotates. The direction of the rotation of the conductor can be determined by Fleming’s Left hand rule.

Question 3:
What is the role of split ring in an electric motor?

Split ring plays the role of commutator in an electric motor. The commutator reverses the direction of the current flowing through the coil after each half rotation of the coil. Due to this reversal of current, the coil continues to rotate in the same direction.

## In-Text Questions (Page 236)

Question 1:
Explain different ways to induce current in a coil.

Following are the different ways to induce current in a coil:

1.If the coil is moved rapidly between the two poles of horse shoe magnet, electric current is induced in the coil.
2.When a magnet is moved relative to the coil, an electric current is induced in the coil.

## In-Text Questions (Page 237)

Question 1:
State the principle of an electric generator.

Electric generator works on the principle of electromagnetic induction. In a generator, electricity is generated by rotating a coil in the magnetic field.

Question 2:
Name some sources of direct current.

DC generator and cell are some sources of direct current.

Question 3:
Which sources produce alternating current ?

Alternating current is produced by AC generators of nuclear power plants, thermal power plants, hydroelectric power stations, etc.

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:
(i) two revolution
(ii) one revolution
(iii) half revolution
(iv) one-fourth revolution

c. half revolution
When a rectangular coil is rotated in magnetic field, the direction of the induced current changes once in half revolution. As a result, the direction of the current in the coil remains the same.

## In-Text Questions (Page 238)

Question 1:
Name two safety measures commonly used in electric circuits and appliances.

(i) Earthing and
(ii) Electric fuse.

Question 2:
An electric oven of 2 kW power rating is operated in a domestic electric circuit (220 V) that has a current rating of 5 A. What result do you expect ? Explain.

The current drawn by the electric oven can be calculated using the formula

P = V × I
I = P/V

Substituting the values, we get
I = 2000 W/220 V = 9.09 A
The current drawn by the electric oven is 9.09 A which exceeds the safe limit of the circuit. This causes the fuse to melt and break the circuit.

Question 3:
What precaution should be taken to avoid the overloading of domestic electric circuits?

A few of the precautions to be taken to avoid the overloading of domestic electric circuits are as follows:

1.Connecting too many devices to a single socket should be avoided
2.Using too many appliances at the same time should be avoided
3.Faulty appliances should not be connected to the circuit

## Exercise Questions (Page 240)

Question 1:
Which of the following correctly describes the magnetic field near a long straight wire ?
(i) the field consists of straight lines perpendicular to the wire
(ii) the field consists of straight lines parallel to the wire
(iii) the field consists of radial lines originating from the wire
(iv) the field consists of concentric circles centred on the wire

d. The field consists of concentric circles centered on the wire.
The magnetic field near a long straight wire are concentric circles. Their centers lie on the wire.

Question 2:
The phenomenon of electromagnetic induction is
(i) the process of charging a body
(ii) the process of generating magnetic field due to a current passing through a coil
(iii) producing induced current in a coil due to relative motion between a magnet and the coil
(iv) 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.
The phenomenon of inducing current in a coil due to the relative motion between the coil and the magnet Is known as electromagnetic induction.

Question 3:
The device used for producing electric current is called a
(i) generator
(ii) galvanometer
(iii) ammeter
(iv) motor

a. generator
The device used for producing electric current is known as generator. Generator converts mechanical energy to electric energy.

Question 4:
The essential difference between an AC generator and a DC generator is that
(i) AC generator has an electromagnet while a DC generator has permanent magnet
(ii) DC generator will generate a higher voltage
(iii) AC generator will generate a higher voltage
(iv) AC generator has slip rings while the DC generator has a commutator

d. AC generator has slip rings while the DC generator has a commutator.
AC generators have two rings known as the slip rings while DC generators have two half rings known as the commutator. This is main difference between AC generator and DC generator.

Question 5:
At the time of short circuit, the current in the circuit
(i) reduces substantially
(ii) does not change
(iii) increases heavily
(iv) varies continuously

c. increases heavily
When two naked wires in the circuit come in contact with each other, the amount of current flowing in the circuit increase abruptly resulting in short circuit.

Question 6:
State whether the following statements are True or False.
(i) An electric motor converts mechanical energy into electrical energy.
(ii) An electric generator works on the principle of electromagnetic induction.
(iii) The field at the centre a long circular coil carrying current will be parallel straight lines.
(iv) 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
An electric generator is a device that generates electricity by rotating a coil in a magnetic field.

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

d. False
Live wires have red insulation cover while the earth wire has green insulation.

Question 7:
List two methods of producing magnetic fields.

(i) Current carrying conductor
(ii) Electromagnets
(iii) Permanent magnets

Question 8:
How docs 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.

A solenoid behaves like a magnet in the following ways.

1.The magnetic field produced by a current carrying solenoid is very much similar to that of a bar magnet.
2.Like a bar magnet, one end of the solenoid has N-polarity while the other end has S-polarity.

To determine the north and south poles, we bring N-pole of the bar magnet near one end of the solenoid. If there is an attraction, then that end of the solenoid has south polarity and the other has north polarity. If there is a repulsion, then that end of the solenoid has north polarity and the other end has south polarity because similar poles repel each other.

Question 9:
When is the force experienced by a current-carrying conductor placed in a magnetic field largest ?

When the conductor carries current in a direction perpendicular to the direction of the magnetic field, the force experienced by the conductor 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 the magnetic field can be determined using the Fleming’s Left hand rule. The direction of the magnetic field will be perpendicular to the direction of current and the direction of deflection, i.e., either upward or downward. The direction of the current is from the front wall to the back wall because negatively charged electrons move from the back wall to the front wall. The directed of the magnetic force is rightward. Hence, using Fleming’s left hand rule it can be concluded that the direction of the 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?

An electric motor is a device that converts electrical energy to mechanical energy. It works on the principle of magnetic effect of current. The figure listed below shows a simple electric motor.

When current is made to flow through the coil MNST by closing the switch, the coil starts to rotate in the anticlockwise direction. This is due to the downward force acting on the length MN and simultaneously an upward force acting along the length ST. As a result of which the coil rotates in the anticlockwise direction. Current in the length MN flows from M to N and the magnetic fields act from left to right normal to the length MN. According to Fleming’s Left Hand rule, a downward force acts along the length MN. Similarly, the current along the length ST flows from S to T and the magnetic field acts from left to right. Therefore, an upward force acts along the length ST. These two forces together cause the coil to rotate anti-clockwise. After half a rotation, the position of MN and ST interchange. The half ring C come in contact with brush B and the half ring D comes in contact with rush C. Hence the direction of current in the coil MNST gets reversed.

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

Electric motor is used in the appliances like electric fans, washing machine, mixers, grinders, blenders, computers, MP3 players, etc.

Question 13:
A coil of insulated copper wire is connected to a galvanometer. What will happen if a bar magnet is (t) pushed into the coil (ii) withdrawn from inside the coil (iii) held stationary inside the coil ?

(i) As a bar magnet is pushed into the coil, a momentary deflection is observed in the galvanometer indicating the production of a momentary current in the coil.
(ii) When the bar magnet is withdrawn from the coil, the deflection of galvanometer is in opposite direction showing the production of an opposite current.
(iii) When the bar magnet is held stationary inside the coil, there is no deflection in galvanometer indicating that no current is produced in the coil.

Question 14:
Two circular coils A and B are placed closed to each other. If the current in the coil A is changed, will some current be induced in the coil B ? Give reason.

Yes, some current will be induced in the coil B. When the current in coil A is changed, some current is induced in the coil B. Due to change in current in coil A, the magnetic field lines linked with coil A and with coil B get changed. This sets up induced current in coil B.

Question 15:
State the rule to determine the direction of a (i) magnetic field produced around a straight conductor-carrying current (it) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and (in) current induced in a coil due to its rotation in a magnetic field.

(i) Right hand thumb rule : If the current carrying conductor is held in the right hand such that the thumb points in the direction of the current, then the direction of the curl of the fingers will give the direction of the magnetic field.
(ii) Fleming’s left hand rule : NCERT Solutions for Class 10 Science Chapter 13 Magnetic Effects of Electric Current Stretch the forefinger, the central finger and the thumb of the left hand mutually perpendicular to each other. If the forefinger points in the direction of the magnetic field, the middle finger in the direction of current, then the thumb points in the direction of force in the conductor.
(iii) Fleming’s right hand rule : Stretch the thumb, forefinger and the central finger of the right hand mutually perpendicular to each other. If the forefinger points in the direction of magnetic field, thumb in the direction of motion of the conductor, then the middle finger points in the direction of current induced in the conductor.

Question 16:
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?

Principle : The electric generator is based on the principle of electromagnetic induction. When a coil is rotated with respect to a magnetic field, the number of magnetic field lines through the coil changes. Due to this a current is induced in the coil whose direction can be found by Fleming’s right hand rule.

Working : When the armature coil ABCD rotates in a magnetic field produced by the permanent magnets, it cuts through the magnetic lines of force.
Due to the rotation of armature coil, the associated magnetic field changes and an induced electromagnetic force is produced in it. The direction of this induced electromotive force or current can be determined by using Fleming’s right hand rule.
In first half cycle the current flows in one direction by brush B1 and in second it flows in opposite direction by brush B2. This process continues. So the current produced is alternating in nature.
Functions of Brushes : Brushes in contact with rings provide the current for external use.

Question 17:
When does an electric short circuit occur ?

In a domestic circuit, short-circuit occurs when live and neutral wire come in direct contact with each other without any resistance. The resistance of the circuit becomes zero and excessive current starts to flow through it.

Question 18:
What is the function of an earth wire? Why is it necessary to earth metallic appliances?

The metallic body of electric appliances is earthed by means of earth wire. Any leakage of electric wire is transferred to the ground by means of earth wire. This prevents the user of the electric appliance from getting electric shocks. This is the reason why it is important for the metallic appliances to be earthed.