# Class 10 Science Chapter 13 NCERT Solution Exercise

Chapter 13 of Science Subject of Class 10 is “Magnetic Effect of Electric Current” .NCERT Solutions (Intext and End Exercise Questions) for Science Chapter 13 are provided on this page.

Contents

## Class 10 Science Chapter 13 – Magnetic Effect of Electric Current

Chapter 13 of Class 10 Science NCERT Text book is “Magnetic Effect of Electric Current”. The end exercise of this chapter consists of a total of 18 questions. These end exercise questions are related to Magnetic effects of current, generator, working of motor and generator, generation of current via magnet, etc

## Chapter 13 : Magnetic Effect of Electric Current ( NCERT Solutions )

Class 10 Science Chapter 13 Question 1 :
Which of the following correctly describes the magnetic field 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.

Answer and Explanation : Option [ d] “The field consists of concentric circles centred on the wire.is correct answer.

Class 10 Science Chapter 13 Question 2 :
The phenomenon of electromagnetic 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.

Answer and Explanation : Option [ c] “producing induced current in a coil due to relative motion between a magnet and the coil.is correct answer.
The phenomenon of electromagnetic induction is producing induced current in a coil due to relative motion between a magnet and the coil.

Class 10 Science Chapter 13 Question 3 :
The device used for producing electric current is called a

(a) generator.
(b) galvanometer.
(c) ammeter.
(d) motor

Answer and Explanation : Option [ a ] “Generator ” is correct answer.
The device used for producing electric current is called a generator.

Class 10 Science Chapter 13 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

Answer and Explanation : Option [ d ] “AC generator has slip rings while the DC generator has a commutatoris correct answer.
The essential difference between an AC generator and a DC generator is that AC generator has slip rings while the DC generator has a commutator.

Class 10 Science Chapter 13 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.

Answer and Explanation : Option [ c ] “increases heavilyis correct answer.
At the time of short circuit, the current in the circuit increases heavily.

Class 10 Science Chapter 13 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 centre 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.

Answer and Explanation :
(a) False
(b) True
(c) True
(d) False

Class 10 Science Chapter 13 Question 7 :
List two methods of producing magnetic fields.

Answer and Explanation :
Magnetic fields can be produced via following methods :
1. A current carrying solenoid – Electromagnet
2. A current carrying conductor.
3. A natural Magnet – Earth’s Magnet
4. Permanent Magnets

Class 10 Science Chapter 13 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.

Answer and Explanation :
The magnetic field at the centre of a solenoid is along the axis . So when the current is passed in a solenoid, the magnetic fields ( due to all circular turns) are added and hence the field line become similar to the field line for a bar magnet.

Yes, we can determine the North and South pole of a current carrying solenoid with the help of a bar magnet . For this we suspend the bar magnet freely and note its ends pointing along North and South direction. Mark on these ends as N & S . Now we bring N pole near one end of solenoid . If there is repulsion then it is North Pole and if there is attraction then it will be the south pole of the solenoid.

Class 10 Science Chapter 13 Question 9 :
When is the force experienced by a current–carrying conductor placed in a magnetic field largest ?

Answer and Explanation :
When the magnetic field and direction of current flowing through the conductor are perpendicular to each other then there is maximum force experienced by a current carrying conductor in a magnetic field.

Class 10 Science Chapter 13 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?

Answer and Explanation :
The magnetic field is perpendicular to the plane containing the beam of electron and the force acting on it .
OR
The direction of magnetic field is vertically downward.

Class 10 Science Chapter 13 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?

Answer and Explanation :
Principle of Electric Motor
When a rectangular coil is placed in a magnetic field and a current is passed through it, a force acts on the coil which rotates it continuously .

Working of an Electric Motor
Current in the coil ABCE enters from the source battery through conducting brush X and flows back to the battery through the brush Y.

Note that current in arm AB of the coil flows from A to B . In the arm CD, the current flows from C to D. By using / applying Fleming’s left hand rule, we find that the arm AB is pushed downward and arm CD is pushed upward .Thus the coil and the axle O, mounted free to turn about an axis, rotate anticlockwise.
At half rotation, Q makes contact with the brush X and P makes contact with the brush Y . Therefore the current in the coil gets reversed and flow along the path DCBA.

The reversal of the current also reverses the direction of forces acting on two arms AB & CD. Again thus whole process takes place giving rise to a continuous rotation. The motor starts working.

Function of Split Rings : – Split rings act as a commutator which reverses the direction of flow of current.

Class 10 Science Chapter 13 Question 12 :
Name some devices in which electric motors are used
.

Answer and Explanation :
Some device in which electric motors are used : – Cooler , A.C Fan, Motor cycle

Class 10 Science Chapter 13 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?

Answer and Explanation :
(i) When a bar magnet is pushed into the coil then the galvanometer shows the deflection and direction of current.
(ii) When bar magnet is withdrawn from inside the coil then the galvanometer shows the deflection in Opposite side .
(iii) When bar magnet is held stationary inside the coil then No deflection in the galvanometer is observed.

Class 10 Science Chapter 13 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.

Answer and Explanation :
Yes, because when current in coil A is changed , the magnetic fields around A changes , so magnetic field/flux linked with the nearby coils changes . This produces induced current in coil B.

Class 10 Science Chapter 13 Question 15 :
State the rule to determine the direction of a

(i) magnetic field produced around a straight conductor-carrying current,
(ii) force experienced by a current-carrying straight conductor placed in a magnetic field which is perpendicular to it, and
(iii) current induced in a coil due to its rotation in a magnetic field.

Answer and Explanation :
(i) Right hand thumb rule
(ii) Fleming’s Left hand rule
(iii) Fleming’s Right hand rule.

Class 10 Science Chapter 13 Question 16 :
Explain the underlying principle and working of an electric generator by drawing a labelled diagram. What is the function of brushes ?

Answer and Explanation :
Working of Generator
An electric generator, consists of a rotating rectangular coil ABCD placed between the two poles of a permanent magnet. The two ends of this coil are connected to the two rings R1 and R2 . The inner side of these rings are made insulated. The two conducting stationary brushes B1 and B2 are kept pressed separately on the rings R1 and R2 , respectively.

The two rings R1 and R2 are internally attached to an axle. The axle may be mechanically rotated from outside to rotate the coil inside the magnetic field. Outer ends of the two brushes are connected to the galvanometer to show the flow of current in the given external circuit. 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 shown in the below figure. By applying Fleming’s right-hand rule, the induced currents are set up in these arms along the directions AB and CD. Thus an induced current flows in the direction ABCD.

If there are larger numbers 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 to 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. Such a current, which changes direction after equal intervals of time, is called an alternating current (abbreviated as AC). This device is called an AC generator.

Class 10 Science Chapter 13 Question 17 :
When does an electric short circuit occur?

Answer and Explanation :
When the live wire and neutral wires comes in direct contact with each other , a very large amount of current is passed through the circuit. This is said that short circuiting has occurred.

Class 10 Science Chapter 13 Question 18 :
What is the function of an earth wire? Why is it necessary to earth metallic appliances?

Answer and Explanation :
Earth wire provides and easy way to flow current to the earth (zero Potential) . It is necessary to Earth Metallic appliances to save us from electric shock.