Chap 13 : Magnetice Effect of Electric Current www.cbse.

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File Revision Date : 10 July 2019

CBSE Previous Years Chapterwise Questions Exam 2019-2020
CLASS : 10th
CHAPTER 13
SUB : Science
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Magnetice Effect of Electric Current

ONE MARK QUESTIONS

1. Mention the shape of the magnetic field lines around

a current carrying straight conductor.
Ans : [CBSE 2016]
The magnetic field lines around a current carrying
straight conductor are in the form of concentric
circular rings around a conductor.

5. Mention the special feature regarding shape of

magnetic field lines.
Ans : [CBSE 2015]
Magnetic field lines are continuous closed loops.

6. If field lines of a magnetic field are crossed at a point,

what does it indicate?
Ans : [CBSE 2015]
If the magnetic field lines would cross each other then
2. State the observation made by Oersted on the basis
at the same point there would be two directions of
of his experiment with current carrying conductors.
magnetic field which is not possible.
Ans : [CBSE 2016]
NO NEED TO PURCHASE ANY BOOKS
A magnetic field is produced near a current carrying
conductor which last so long till there is current in the For session 2019-2020 free pdf will be available at
conductor on reversing the current the direction of www.cbse.online for
magnetic field is also reversed. 1. Previous 15 Years Exams Chapter-wise Question
Bank
3. State the direction of the magnetic field inside the bar 2. Previous Ten Years Exam Paper (Paper-wise).
magnet. 3. 20 Model Paper (All Solved).
Ans : [CBSE 2016] 4. NCERT Solutions
All material will be solved and free pdf. It will be
In a magnet, magnetic field lines goes from S pole to
provided by 30 September and will be updated regularly.
N pole. Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education,
New Delhi in any manner. www.cbse.online is a private organization which provide free
study material pdfs to students. At www.cbse.online CBSE stands for Canny Books
4. Identify the poles of the magnet in the given figure. For School Education

7. Draw a diagram to represent a uniform magnetic field

in a given region.
Ans : [CBSE 2015]
Uniform magnetic field is represented by equidistant
parallel lines.

Ans : [CBSE 2016]

A1 is North Pole, B1 is South Pole because magnetic 8. What type of core is used to make an electromagnet?
field lines goes from north pole to south pole of the Ans : [CBSE 2015]
magnet. Soft iron core is used in making an electromagnet.

9. State the direction of magnetic field in the following

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

case: 16. What will be the frequency of an alternating current

if its direction changes after every 0.01 s?
Ans : [CBSE 2011]
The direction of ac changes every 0.01 sec.
Thus time of one complete cycle = 0.02 sec
i.e. in 0.02 sec no. of cycle = 1
in 1 sec no. of cycle = 1 = 100 = 50
0.02 2
Ans : [CBSE 2014]
Frequency of ac = 50 Hz
Perpendicular to both current and force on the
conductor outward the plane of paper. 17. What is short-circuiting in an electric supply?
Ans : [CBSE2005]
10. Mention the voltage and frequency of current that we
receive at our house. When a neutral wire and live wire come in contact
Ans : [CBSE 2014] with each other short circuit takes place.

In our house we get AC of voltage 220 V and frequency 18. What constitutes the field of a magnet?
50 Hz. Ans : [CBSE 2006]
11. Name the type of current: (a) used in household The magnetic field is created by the magnet or when
supply (b) given by a cell. a charge particle is moving with some velocity in both
Ans : [CBSE 2014] cases they produce a magnetic field around them. The
magnetic field is due to current or magnetic material.
a. We use alternating current in our houses which
changes to direction and magnitude with time. 19. What is the advantage of the third wire of earth
b. A cell supply direct current (DC) or unidirectional connection in domestic appliances?
current which flows only in one direction only. Ans : [CBSE 2006]
12. State the rule which you use to find the direction of In case of any electric fault in domestic appliances,
induced current or state Fleming’s right hand rule. current may comes in appliance body. The third wire
Ans : [CBSE 2015] called earth wire transfer this current to the earth and
user remains safe from any such electric shock.
Fleming’s right hand rule gives the direction of current
produced in a conductor. According to Fleming’s right 20. How can you show that the magnetic field produced
hand rule, if we stretch right hand thumb, forefinger by a given electric current in the wire decreases as the
and middle finger perpendicular to each other in distance from the wire decreases?
such a way that thumb points the direction of force Ans : [CBSE 2006]
on a conductor and forefinger points the direction
If we bring a magnetic compass from a distance to
of magnetic field then middle finger will point the
near a current carrying conductor its deflection goes
direction of current produced in the conductor.
on increasing and when magnetic compass is brought
13. How can it be shown that a magnetic field exists away from the current carrying wire its deflection goes
around a wire through which a direct current is on decreasing which shows that magnetic field near
passing. current carrying wire is maximum and decreasing on
Ans : [Delhi 2014] increasing the separation.

When we put a small magnetic compass near a current 21. When is the force experienced by a current carrying
carrying conductor it gets deflected, which shows that conductor placed in a magnetic field the maximum?
a magnetic field is produced near a current carrying Ans : [CBSE 2009]
conductor.
A current carrying conductor experience maximum
14. How is the strength of the magnetic field at a point force in a magnetic field when the direction of current
near a wire related to the strength of the electric is perpendicular to the magnetic field.
current flowing in the wire?
22. How is the induced current in a secondary coil related
Ans : [CBSE 2009] to current in a primary coil?
The magnetic field strength at a point near a wire is Ans : [CBSE 2009]
directly proportional to the current strength in the
Induced current in a secondary coil may be more or
conductor.
lesser than the current in primary coil depending upon
15. An alternating electric current has a frequency of 50 the number of turns in secondary.
Hz. How many times does it change its direction in
23. What is the pattern of field fines inside a solenoid?
one second?
What do they indicate?
Ans : [CBSE 2011]
Ans : [CBSE 2010]
50 Hz ac changes its direction 100 times in 1 sec.
The magnetic field inside a solenoid is uniform in the

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

form of parallel lines. A coil of many circular turns of insulated wire wrapped
closely in the form of a cylinder is called a solenoid.
24. How is the magnetic field produced in a solenoid used? In a current carrying solenoid magnetic field is same
Ans : [CBSE 2010] at all points inside it, i.e. field is uniform inside the
Magnetic field produced in a solenoid can be used in solenoid. The magnetic field inside a coil vary.
making a soft iron piece electromagnet.
33. An alpha particle (+ve charged particle) enters a
25. What does the direction of thumb indicate in the magnetic field at right angle to it as shown in figure.
right-hand thumb rule? Explain with the help of a relevant rule, the direction
of force acting on the alpha particle.
Ans : [CBSE 2010]
Thumb points the direction of current in the conductor
holding a straight conductor in right hand.

26. Mention the angle between a current carrying

conductor and magnetic field for which the force
experienced by this current carrying conductor placed
in magnetic field is largest? Ans : [CBSE 2016]
Ans : [CBSE 2012] Force on a-particle will be in the upward direction as
If the angle between a current carrying conductor and per Fleming’s left hand rule.
magnetic field is 90° then the force experienced by the
conductor is maximum. 34. An alternating electric current has a frequency of 50
Hz. How many times does it change its direction in
27. Suggest one way of discriminating a wire carrying one second? Give reason for your answer.
current from a wire carrying no current. Ans : [CBSE 2016]
Ans : [CBSE 2012] 100 times in one second because one complete cycle
When a magnetic compass is brought near a current involves two times change of direction.
carrying conductor it will be deflected. If magnetic
NO NEED TO PURCHASE ANY BOOKS
compass remains undeflected near a conductor then
there is no current in it. For session 2019-2020 free pdf will be available at
www.cbse.online for
28. What does the thumb indicated in Fleming’s right 1. Previous 15 Years Exams Chapter-wise Question
hand rule? Bank
Ans : [CBSE 2012] 2. Previous Ten Years Exam Paper (Paper-wise).
Thumb indicate the direction of force on conductor 3. 20 Model Paper (All Solved).
i.e. motion of the conductor. 4. NCERT Solutions
All material will be solved and free pdf. It will be
29. Why are magnetic field lines closed curves? provided by 30 September and will be updated regularly.
Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education,
Ans : [CBSE 2012] New Delhi in any manner. www.cbse.online is a private organization which provide free
study material pdfs to students. At www.cbse.online CBSE stands for Canny Books
By convention the magnetic field lines are the path For School Education

traced by north pole which emerges from north pole

and goes to the south pole and inside the magnet the
35. (a) Name the type of electric current generated by
direction of field lines are from south pole to north
the most of the power stations in our country.
pole, forming continuous closed path.
(b) Why is it preferred over the other type?
30. Write any one method to induce current in a coil. (c) State the frequency of the power supply generated
in India.
Ans : [CBSE 2013]
Ans : [CBSE 2016]
By moving a magnet towards the coil or vice versa,
current can be induced in the coil. (a) Alternating current
(b) AC can be transmitted at high voltage using step
up transformer to prevent loss in transmission.
TWO MARKS QUESTIONS (c) 50 Hz

36. (a) A compass needle gets deflected when brought

31. State two ways by which the strength of an near a current carrying conductor. Why?
electromagnet can be increased. (b) What happened to the reflection of needle when
Ans : [CBSE 2016] current in the conductor is increased?
By increasing the strength of current and number of Ans : [CBSE 2014]
turns of the solenoid we can increase the strength of (a) Near a current carrying conductor a magnetic
an electromagnet. field is produced which deflect the compass.
(b) With the increase in strength of current in the
32. Define a solenoid. How is it different from a coil? conductor strength of magnetic field also increases
Ans : [CBSE 2016] so there will be more deflection in compass.
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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

37. Draw the patterns of magnetic field fines due to a bar b. Magnetic field lines in a solenoid.
magnet. The magnetic field fines are closed curves.
Why? 40. A compass needle is placed near a current carrying
wire. State your observation for the following cases
Ans : [CBSE 2014]
and give reason for the same in each case:
Magnetic field lines emerge out from the N-pole of a a. Magnitude of electric current in the wire is
bar magnet go to the S-pole and inside the magnet increased.
field lines goes from S-pole to N-pole thus form the b. The compass needle is displaced away from the
closed curves. wire.
Ans : [CBSE 2014]
a. Compass needle is deflected more because more
the current, more the magnetic field near the wire.
b. Magnetic field strength is inversely proportional
to the distance from current carrying wire. So
deflection will decrease in the compass needle
when brought away from wire.

41. What are magnetic field lines? How is the direction

of magnetic field at a point determined? Mention few
important properties of magnetic field lines.
Ans : [CBSE 2016]
38. (a) In a pattern of magnetic field fines due to a bar Magnetic field lines are the path traced by north pole
magnet, how can the regions of relative strength in a magnetic field. A tangent drawn to the magnetic
be identified? field lines gives the direction of magnetic field at that
(b) Compare the strength of field near the poles and point.
middle of a bar magnet. a. Magnetic field lines emerge out from the N-pole
Ans : [CBSE 2014] and go to the south pole and from S-pole to N-pole
(a) More the density of the magnetic field lines i.e. inside the magnet forming the closed curve.
more closer the magnetic field lines more the b. They do not intersect each other.
strength of magnetic field. 42. What is the nature of magnetic field produced by a
(b) Near the poles magnetic field lines are closer than straight current carrying circular coil? Explain with
the middle of a bar magnet. So magnetic strength the help of an experiment.
is more near poles than middle part of bar magnet.
Ans : [Delhi 2015]
39. Identify the type of magnetic fields represented by the Bend a wire in the shape of a circular loop. Pass the
magnetic field fines given below and name the type coil through a cardboard. Connect the free ends of
conductors which can produce them. the coil to a battery and a key. Sprinkle some iron
filings on the cardboard. Put on the key you will find
that the iron filings arrange themselves in the form of
concentric circles. The magnetic lines of forces near
each segment of wire are circular and form concentric
circles, whereas the lines of force near the centre of the
coil are almost straight lines.
The right hand thumb rule predicts the direction
of this magnetic field it states “Grasp the conductor
in the right hand with the thumb pointing in the
direction of current, and then the direction in which
the fingers curl gives the direction of the magnetic
Ans : [CBSE 2014] field.”

43. On what factors does the force experienced by a

current carrying conductor placed in a uniform
magnetic field depend?
Ans : [CBSE 2015]
The force experienced by a current carrying conductor
in a magnetic field depends upon—
a. length of the conductor
b. current in the conductor
c. magnetic field in which it is kept

a. Magnetic field lines of a current carrying circular 44. What is meant by the term “magnetic field lines”?
loop.

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

List two properties of magnetic field lines. whether we require it or not.

Ans : [CBSE 2006] d. In series combination total potential difference
is divided among all appliances in proportion
Magnetic field lines are the path traced by a
to their resistance. So all appliance will not get
hypothetical north pole in the magnetic field of
required voltage to operate efficiently.
another magnet or current carrying conductor if it is
allowed to do so. 47. Explain what is short-circuiting and overloading in an
Properties: electric supply.
a. No two field lines are found to cross each other. Ans : [CBSE 2001]
b. Outside the magnet magnetic field lines travel
from N-pole to S-pole and inside the magnet from When live wire and neutral wire come in contact with
S-pole to N-pole. each other short circuit takes place. This may be due
to fault in electric circuit or when insulation of wire is
45. With the help of a neat diagram, describe how you damaged. During the short circuiting current increases
can generate induced current in a circuit. abruptly due to decrease in resistance in the circuit.
Ans : [CBSE 2006] This short circuiting leads the spark and house may
catch fire.
Take a coil of large number of turns and connect the
two ends of the coil with a galvanometer. Galvanometer Over loading means to draw the current by all
is a device used to detect the presence of current. electric appliances in the circuit more than maximum
permitted value of the current, overloading also leads
Now bring N pole of a strong magnet towards
the heating of wires which may damage the insulation
the coil. There is a momentary deflection in the
of wires.
galvanometer. Now bring the N pole away from
the coil, again there is a deflection in the opposite NO NEED TO PURCHASE ANY BOOKS
direction in the galvanometer deflection in the
For session 2019-2020 free pdf will be available at
galvanometer shows that a current is induced in the
www.cbse.online for
coil. The induced current can be produced by keeping
1. Previous 15 Years Exams Chapter-wise Question
magnet stationary and giving movement to the coil,
Bank
or when both have a relative motion w.r.t. each other.
2. Previous Ten Years Exam Paper (Paper-wise).
3. 20 Model Paper (All Solved).
4. NCERT Solutions
All material will be solved and free pdf. It will be
provided by 30 September and will be updated regularly.
Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education,
New Delhi in any manner. www.cbse.online is a private organization which provide free
study material pdfs to students. At www.cbse.online CBSE stands for Canny Books
For School Education

48. State the characteristics of magnetic force.

Ans : [CBSE 2002]
If a charge is moving in a magnetic field then
it experiences a force known as magnetic force
F = qVB sin q , B is magnetic force, q is angle between
B and V. This magnetic force
a. acts only when charge is moving
b. does not act when charge is at rest
c. is maximum when charge is moving perpendicular
to the magnetic field
d. does not act when charge is moving in the same
direction of magnetic field.

49. The flow of a current in a circular loop of a wire creates

46. Why is series arrangement not used for domestic a magnetic field at its centre. How can existence of
circuits? this field be detected? State the rule which helps to
Ans : [CBSE 2001] predict the direction of this magnetic field.
Ans : [CBSE 2004]
In domestic circuits, all appliances are connected in
parallel not in series because Take a cardboard and fix it. Now pass a thick copper
a. In series combination same current is passed wire having two holes giving the wire a circular shape.
through each appliances whereas they may need Connect the two ends of the wire with a cell and plug
different current. key. Sprinkle iron filings uniformly on the cardboard.
b. If one appliance fails to work then circuit will be Now plug in key and tap the cardboard gently a
broken and all other appliances will stop to work. number of times. The iron filings arrange themselves in
c. If one appliance is switched off others also will the pattern of concentric circles. Near each segment of
stop working i.e. all appliance will work together wire whereas near the centre of the coil these arrange

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

almost in straight lines. Right hand thumb rule gives Ans : [CBSE 2004]
the direction of magnetic field i.e. if we hold a current The pattern of magnetic lines of force is in the form
carrying conductor in our right hand in such way that of concentric circles around the current carrying wire.
thumb points the direction of current, then the curls
of the fingers encircling the conductor will give the
direction of magnetic field around the conductor.

NO NEED TO PURCHASE ANY BOOKS

For session 2019-2020 free pdf will be available at
www.cbse.online for
1. Previous 15 Years Exams Chapter-wise Question
Bank
2. Previous Ten Years Exam Paper (Paper-wise).
3. 20 Model Paper (All Solved).
4. NCERT Solutions a. with the increase in current, magnetic field around
All material will be solved and free pdf. It will be the conductor also
provided by 30 September and will be updated regularly.
Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education,
New Delhi in any manner. www.cbse.online is a private organization which provide free
study material pdfs to students. At www.cbse.online CBSE stands for Canny Books
For School Education

50. How does the strength of the magnetic field at the

centre of a circular coil of wire depend on: (i) the
radius of the coil (ii) the number of turns of wire in
the coil (iii) the strength of the current flowing in the
coil?
b. near the current carrying conductor magnetic field
Ans : [CBSE 2004] is more which decreases with increase in distance
The magnetic field at the centre of a current carrying from the wire.
circular coil is
NO NEED TO PURCHASE ANY BOOKS
a. inversely proportional to the radius ‘a’ of the coil
B \ a1 For session 2019-2020 free pdf will be available at
b. directly proportional to the number of turns in www.cbse.online for
the coil 1. Previous 15 Years Exams Chapter-wise Question
c. directly proportional to the current I in the coil Bank
B\I. 2. Previous Ten Years Exam Paper (Paper-wise).
3. 20 Model Paper (All Solved).
4. NCERT Solutions
All material will be solved and free pdf. It will be
provided by 30 September and will be updated regularly.
Disclaimer : www.cbse.online is not affiliated to Central Board of Secondary Education,
New Delhi in any manner. www.cbse.online is a private organization which provide free
study material pdfs to students. At www.cbse.online CBSE stands for Canny Books
For School Education

52. Draw the pattern of lines of force due to a magnetic

field through and around a current carrying loop of
wire. How would the strength of the magnetic field
51. Draw the pattern of lines of force due to a magnetic produced at the centre of the circular loop be affected
field associated with a current carrying conductor. if
State how the magnetic field produced changes a. the strength of the current passing through this
a. with an increase in current in the conductor and loop is double?
b. the distance from the conductor. b. the radius of the loop is reduced to half of the

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

original radius? (1)

Ans : [CBSE 2004]
The pattern of lines of force due to a magnetic field
through and around a current carrying loop of wire is
shown below (2)
Ans : [CBSE 2010]
The figure is as shown below :

a. Strength of magnetic field is doubled when the

current through the loop is doubled B \ I .
b. Strength of magnetic field is doubled when the 56. What are permanent magnet and electromagnet?
radius of the loop is halved B \ r1 . Give two uses of each.
Ans : [CBSE 2010]
53. Draw the pattern of field lines due to a solenoid
Permanent Magnet: It has constant magnetic field
carrying electric current. Mark the north and south
around it. e.g. generator, loud speaker.
poles in the diagram.
Electromagnet: When a soft iron is placed in a solenoid
Ans : [CBSE 2004] it gets magnetised till there is current in solenoid, e.g.
The pattern of the magnetic field lines is as shown in electric bells, cranes.
figure.
57. Explain briefly different methods of producing induced
emf.
Ans : [CBSE 2010]
a. By mutual induction: If we change current in one
coil, a current is induced in the neighbouring coil.
b. By giving a relative motion to a magnet and coil
in its neighbourhood.

58. What is the role of fuse, used in series with any

electrical appliance? Why should a fuse with defined
rating not be replaced by one with a larger rating?
54. Differentiate overloading and short- circuiting.
Ans : [CBSE 2010]
Ans : [CBSE 2010] Fuse wire is safety device to prevent electrical devices
due to short circuiting or overloading. The fuse wire
Overloading means to draw current more than the
is rated for a maximum current which has high
permitted maximum current in the circuit which may
resistance and low melting point. When there is short
be due to connecting many appliances in one socket.
circuiting large current is passed in the circuit. Due
In short circuiting, when live wire and neutral to large current in fuse wire heat is produced and
wire come in contact with each other then resistance by melting fuse wire breaks the circuit to keep other
of the circuit becomes minimum consequently the appliances safe.
current in the circuit increases abruptly. It may be
If a fuse wire is replaced by an ordinary copper
due to damage of insulation of wire.
wire which has low resistance and high melting point
55. Identify the poles of the magnet in the given figure it will not melt and domestic appliance may get
(1) and (2). damaged due to excessive heat due to short circuiting
or overloading.

59. A magnetic compass shows a deflection when placed

near a current carrying wire. How will the deflection
of the compass get affected if the current in the wire is
increased? Support your answer with a reason.
Ans : [CBSE 2010]
If current is increased magnetic field around this

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

conductor increases, the deflection in the galvanometer Which of the two observations is correct and why?
also increases. Ans : [CBSE 2011]
60. No two magnetic field lines can intersect each other. First observation is correct because when current
Explain. increases force also increase. From equation of force on
Ans : [CBSE2010] a current carrying conductor F = BIl. F \ I i.e. more
current more force on a current carrying conductor in
If two magnetic field lines intersect each other then a magnetic field.
at the point of intersection there will be two different
tangents pointing two different directions of magnetic 65. An electron enters a uniform magnetic field at right
field at a point which is not possible. angles to it as shown in the figure below. In which
direction will this electron move? State the rule
61. What is meant by the term magnetic field lines? List applied by you in finding the direction of motion of
any two properties of magnetic field lines. the electron.
Ans : [CBSE 2010]
The imaginary path traced by N-pole of a magnet in a
magnetic field is called magnetic field lines.
Properties:
a. Two magnetic field lines never intersect each
other.
b. Magnetic field lines are crowded near the poles
and near the mid part of magnets the density of
magnetic lines of force decreases.

62. Why does a current carrying Conductor experiences Ans : [CBSE 2011]
a force when it is placed in a magnetic field? State
As per Fleming’s left hand rule the electron
Fleming’s left hand rule.
will experience a force upward. So it will move
Ans : [CBSE 2011] perpendicularly outward.
When a current carrying conductor is placed in
a magnetic field it experiences a force due to
interaction between the two magnetic fields due to
current carrying , conductor and given magnetic field
of a magnet. If we hold our thumb, forefinger, and
middle finger perpendicular to each other in such a
way that forefinger points the direction of magnetic
field, middle finger points the direction of charge q
(direction of current in conductor), then thumb will
point the direction force acting upon the conductor.
Fleming’s left hand rule -stretch the forefinger,
63. A student performs an experiment to study the
the middle finger and the thumb of the left hand
magnetic effect of current around a current carrying
mutually perpendicular to each other in such a way
straight conductor with the help of a magnetic
that forefinger points the direction of magnetic field,
compass. He reports that:
middle finger points the direction of current (opposite
a. the degree of deflection of the magnetic compass
to the flow of electrons) then the thumb will point the
increases when the compass is moved away from
direction of force on the conductor (charge).
the conductor.
b. the degree of deflection of the magnetic compass 66. (a) What is the direction of magnetic field lines inside
increases when the current through the conductor a bar magnet and outside of it?
is increased. (b) What does the degree of closeness of the field lines
Which of the above observations of the student represent?
appears to be wrong and why?
Ans : [CBSE 2011]
Ans : [CBSE 2011]
The direction of magnet lines of force inside a bar
The first statement is wrong because the strength of magnet is from S-pole to N-pole. Outside the bar
magnetic field decreases when we move away from magnet these emerge out from N-pole and go to the
a current carrying conductor. So deflection in the
compass, instead of increasing must decrease. 67. A magnetic compass shows a deflection when placed
near a current carrying wire. How will the deflection
64. A student while studying the force experienced by a of the compass get affected, if the current in the wire
current carrying conductor in a magnetic field records is increased? Support your answer with a reason.
the following observations:
Ans : [CBSE 2011]
a. The force experienced by the conductor increases
as the current is increased. If the strength of current is increased then deflection
b. The force experienced by the conductor decreases of compass also increase because magnetic field is
as the strength of the magnetic field is increased. directly proportional to the current in the conductor.

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

More magnetic field more deflection in the compass. a. \ r1 , i.e. magnetic field decreases with increase in
radius.
68. Draw magnetic field lines produced around a b. \ n , i.e. magnetic field increases with increase in
current carrying straight conductor passing through number of turns.
cardboard. How will the strength of the magnetic field
change, when the point where magnetic field is to be 71. Name and state the rule to determine the direction
determined, is moved away from the straight wire of a force experienced by a current carrying straight
carrying constant current? Justify your answer. conductor placed in a magnetic field which is
Ans : [CBSE 2012] perpendicular to it. Name a device that uses current
carrying conductor and magnetic field.
The strength of the magnetic field decreases when
the point where magnetic field is to be determined is Ans : [CBSE 2012]
moved away from the wire. Fleming’s left hand rule gives the direction of force
experienced by a current carrying straight conductor
placed in a magnetic field which is perpendicular to
it. According to Fleming’s left hand rule if we stretch
our left hand thumb, forefinger and middle finger
in such a way that forefinger points the direction of
magnetic field, middle finger points the direction of
current then thumb will give the direction of force on
the conductor.

69. Magnetic field lines are shown in the given diagram.

A student makes a statement that magnetic field
at X is stronger than at Y. Justify this statement.
Also, redraw the diagram and mark the direction of
magnetic field lines. NO NEED TO PURCHASE ANY BOOKS
For session 2019-2020 free pdf will be available at
www.cbse.online for
1. Previous 15 Years Exams Chapter-wise Question
Bank
2. Previous Ten Years Exam Paper (Paper-wise).
3. 20 Model Paper (All Solved).
4. NCERT Solutions
All material will be solved and free pdf. It will be
Ans : [CBSE 2012] provided by 30 September and will be updated regularly.
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strength of magnetic field.

THREE MARKS QUESTIONS

72. (a) State Fleming’s left hand rule.

(b) Write the principle of working of an electric motor.
(c) Explain the function of the following parts of an
electric motor.
(i) Armature, (ii) Brushes, (iii) Split ring
Ans : [CBSE 2017]
70. How does the strength of the magnetic field at the (a) Fleming’s left hand rule: If we stretch thumb,
centre of a circular coil of a wire depend on: forefinger and middle finger of left hand
a. radius of the coil perpendicular to each other in such a way that
b. number of turns in the coil. forefinger points in the direction of magnetic field,
Ans : [CBSE 2012] middle finger points in the direction of current
then the thumb will point in the direction of
Magnetic field strength at the centre of a circular coil
motion/force on the current carrying conductor.
of a wire carrying current
(b) Principle of working of electric motor: A current

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

carrying coil placed in a magnetic field experience 75. Define magnetic field. Describe an activity to draw
a torque. If the coil is free to move it will rotate in magnetic field lines around a bar magnet from one
the magnetic field. pole to another pole.
(c) (i) Armature: The soft iron core on which the coil Ans : [CBSE 2016]
is wound along with coils is called armature which
Magnetic field is the space around a magnet or a
enhances the power of motor.
current carrying conductor in which its magnetic force
(ii) Brushes: Brushes help in transfer of current
can be experience.
between coil and external circuit.
(iii) Split rings reverses the direction of current Fix a plane white drawing sheet on a drawing
after every half rotation of the coil so that the board. Now take a bar magnet and a compass. Place
direction of torque/force on the coil remains the magnet at the middle of the paper and mark its
and it continuous to rotate. boundary with the help of a pencil. Now place the
compass near its N pole of the magnet and marks
73. For the circular coil carrying current shown alongside, the positions of needle of the compass. Now move the
draw magnetic field lines. Decide which of its face compass on the drawing board. Coinciding south pole
behaves as North Pole and which face as South Pole. of the compass with the previous marked point of N
Give reason to justify your answer. pole of the needle and so on, move forward from one
end
(N pole) to the another end (S pole) of the bar magnet.
Join all the marked points. You will get magnetic lines
of force.

Ans : [CBSE 2014, 2016]

From the front face magnetic field emerges out of the
coil and enters out from the back face so front face
will behave as north pole and back face as south pole.

76. Find the minimum rating of fuse that can be safely

used on a line on which two 1.1 kW, electric geysers
are to run simultaneously. The supply voltage is 220
V.
Ans : [CBSE 2015]

I = Total Power = nP
V V

= 2 # 1.1 kW
220 V

= 2 # 1.1 # 1000 W = 10 A
220 V
74. A uniform magnetic field is directed vertically So a fuse wire of rating must be greater than 10 A.
upwards. In which direction in this field should an
a-particle (which are positively charged particles) be 77. Can a freely suspended current carrying solenoid
projected so that it is deflected south ward? Name stay in any direction? Justify your answer. What will
and state the rule you have used to find the direction happen when the direction of current in the solenoid
in this case. is reversed? Explain.
Ans : [CBSE 2016] Ans : [CBSE 2015]
Forefinger - direction of magnetic field (upwards). No, current carrying solenoid behaves like a bar
Thumb - direction of force (southwards) Middle finger magnet and will stay only geographical N and S
gives direction of current or direction of positively direction. If the direction of current is reversed then
charged particle (East) i.e. from west to east a particles the polarity of the magnet will change and hence will
must be projected. rotate through an angle of 180°.

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

78. What is meant by electromagnetic induction? State carrying circular coil changes, if we increase the:
the rule which helps in determining direction of a. value of current flowing through it?
induced current. b. distance of point P from the coil?
Ans : [CBSE 2015] c. number of turns of the coil?
Electromagnetic induction is the phenomenon of Ans : [CBSE 2011, 2014]
production of emf (potential difference) or current a. Magnetic field is directly proportional to current
in a coil due to change in magnetic field around it. so magnetic field increases when current increases.
Fleming right hand rule: If we stretch our right hand b. If we increase the distance of point P, magnetic
thumb, forefinger and middle finger perpendicular to field decreases.
each other in such a way that forefinger points the
direction of magnetic field, and thumb points the
direction of force acting on the conductor (motion
of the conductor), then the middle finger points the
direction of induced current in the conductor.

79. Horizontal component of earth’s magnetic field at a

place is uniform and its direction is south to north. A
high current through a horizontal power line flows at
this place from west to east. Consider two points A
and B at equal distances from the wire, respectively
above and below it. Giving reason explain where is the
field more at A or at B. c. On increasing the number of turns magnetic field
Ans : [CBSE 2014] increasing.

The direction of magnetic field due to current at A 82. What happens to the deflection of the compass needle
is from north to south and at B from south to north. placed at a point near current carrying straight
Therefore, at A earth’s magnetic field and field due to conductor:
current are in opposite direction and at B earth’s a. if the current is increased?
magnetic field and magnetic field due to current are b. if the direction of current in the conductor is
in same direction. changed (reversed)?
c. if compass is moved away from the conductor?
Ans : [CBSE 2011, 2014]
a. If the current increases deflection of compass
increases.
b. If the direction of current is reversed the deflection
in the compass needle is also reversed.
c. Deflection of the compass needle decreases when
compass is moved away from the conductor.

83. Name any three factors on which the magnitude of the

magnetic field due to solenoid depends.
Ans : [CBSE 2014]
Factors on which the magnitude of the magnetic field
80. A coil of insulated wire is connected to a galvanometer.
due to solenoids
Explain what happens if a bar magnet with its north
a. number of turns in the solenoid
pole towards one face of the coil is:
b. area of cross section of the coil
a. moved quickly towards the coil,
c. strength of current in solenoid
b. kept stationary inside the coil, and
c. moved quick away from the coil? 84. State the condition for electromagnetic induction to
Ans : [CBSE 2014] take place. A cylindrical bar magnet is kept along the
When a bar magnet is moved towards the coil there is axis of a circular coil as shown in the figure. Will
change in magnetic field in there be a current induced in the coil if the magnet is
a. coil so a current is induced in the coil so rotated about its axis? Discuss.
galvanometer gives a deflection.
b. when magnet is kept stationary in the coil then
due to no change in the magnetic field no current
is induced in the coil.
c. when magnet is moved quickly away from the coil
again there is change in magnetic field associated
with the coil so again a current is induced but in
the opposite direction.
Ans : [CBSE 2014]
81. How will the magnetic field produced in a current
Electromagnetic induction

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

a. Either coil or magnet or both must have a relative 87. (a) Electric fuse is an important component of all
motion between them. domestic circuits. Why?
b. If there is a change in current in a coil then current (b) An electric oven of rating 2 kW, 220 V is operated
will be induced in the another neighbouring coil. in a domestic circuit with a current rating of 5 A.
No current is induced because there is no change What result would you expect? Explain.
in magnetic field. Ans : [CBSE 2010]
Electric fuse is a safety device which has high resistance
85. Draw a diagram to show how a magnetic needle
and low melting point and prevents electric appliances
deflects when it is placed above or below a straight
during short circuiting and overloading. By melting
conductor carrying current depending on the direction
itself, a fuse break the circuit.
of the current in the conductor.
Ans : [CBSE 2010] 88. Name two safety measures commonly used in electric
circuits and appliances, what precautions should be
taken to avoid the over loading of domestic electric
circuits?
Ans : [CBSE 2010]
Proper earthing and using a fuse load in the electric
circuit must be as per rating of the fuse and do not
connect to many plugs in a single socket.

89. Why does a current carrying conductor kept in a

magnetic field experience force? On what factors does
the direction of this force depend? Name and state the
86. (a) Describe an activity to draw a magnetic field line rule used for determination of direction of this force.
outside a bar magnet from one pole to another. Ans : [CBSE 2010]
(b) List any two properties of magnetic field lines.
Around a current carrying conductor a magnetic field
Ans : [CBSE 2010] is produced. When it is placed in a magnetic field then
(a) Fix a plane white drawing sheet on a drawing both fields interact each other, and current carrying
board. Now take a bar magnet and a compass. conductor experience a force.
Place the magnet at the middle of the paper and Fleming’s left hand rule: If we stretch right hand
mark its boundary with the help of pencil. Now thumb, forefinger and middle finger perpendicular
place compass near N-pole of bar magnet and the to each other in such a way that forefinger points
position of needle of the compass. Now move the the direction of magnetic field, middle finger points
compass on the drawing board coinciding S-pole the direction of current, then thumb will point the
of the compass with the previous marked point of direction of force on the conductor.
N of the needle and so on move forward from one
end (N-pole) to the S-pole of the bar magnet. Join 90. What does the direction of thumb indicate in the right
all the marked points. You will get magnetic lines hand thumb rule? In what way this rule is different
of force. from Fleming’s left hand rule?
Ans : [CBSE 2010]
Thumb indicate the direction of current in a straight
conductor held in right hand. Fleming’s left hand
rule gives the direction of force on a current carrying
conductor placed in magnetic field.
Fleming’s left hand rule : If we stretch right hand
thumb, forefinger and middle finger perpendicular
to each other in such a way that forefinger points
the direction of magnetic field, middle finger points
the direction of current, then thumb will point the
direction of force on the conductor.

91. Under what condition does a current carrying

conductor kept in a magnetic field experience
maximum force? On what other factors does the
magnitude of this force depend? Name and state the
rule used for determination of direction of this force.
(b) Properties of magnetic field lines. Ans : [CBSE 2011]
(i) Magnetic field lines do not intersect each
other. Force on a current carrying conductor in a magnetic
(ii) Magnetic field lines emerge out at N-pole and field depends upon
goes to the S-pole whereas in magnet these a. length of the conductor
travel from S-pole to N-pole. b. strength of the magnetic field
c. strength of the current

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

d. angle between direction of magnetic field and b. AG generators are used to produce AC.
current. c. AC voltage can be increased or decrease with the
Fleming’s Left Hand Rule: help of a transformers.
Fleming’s left hand rule gives the direction of force 95. State one main difference between ac and dc. Why
experienced by a current carrying straight conductor ac is preferred over dc for long range transmission of
placed in a magnetic field which is perpendicular to electric power? Name one source each of dc and ac.
it. According to Fleming’s left hand rule if we stretch
our left hand thumb, forefinger and middle finger Ans : [CBSE 2012]
in such a way that forefinger points the direction of The magnitude and direction of ac remains same
magnetic field, middle finger points the direction of whereas a.c. changes its magnitude and direction
current then thumb will give the direction of force on periodically. Low AC voltage can be increase to high
the conductor. voltage to prevent loss in electric energy during its
long distance transmission.
AC generator and DC generator/or cell.

96. (a) Mention the colour code used for live, neutral and
earth wire.
(b) You want to connect a 2 kW electric oven in the
electric circuit. In which power line would you
connect it and why? What may happen if you
connect it wrongly in the other power line?
Ans : [CBSE 2013]
(a) Live wire – Red
92. A coil made of insulated copper wire is connected to
a galvanometer. What will happen to the deflection Neutral wire – Black
of the galvanometer if this coil is moved towards a Earth wire – Green
stationary bar magnet and then moved away from it? (b) 2 kW electric iron draws large current. If it is
Give reason for your answer and name the phenomenon connected to a socket of 5Athen fuse will be
involved. blown. So it is connected in power socket of 15 A.
Ans : [CBSE 2011]
In both the case there is a change in magnetic field FIVE MARKS QUESTIONS
associated with the coil, an induced current is produced
in the coil, but in opposite direction. This phenomenon
is called electromagnetic induction (EMI). 97. (a) State Fleming’s left hand rule.
(b) Write the principle of working of an electric motor.
93. What is meant by overloading of an electrical circuit?
(c) Explain the function of the following parts of an
Explain two possible causes due to which overloading electric motor.
may occur in household circuit. Explain one precaution
that should be taken to avoid the overloading of (i) Armature (ii) Brushes (iii) Split ring
domestic electric circuit. Ans : [CBSE 2017]
Ans : [CBSE 2012] (a) Fleming’s left hand rule state that if the thumb,
Connecting large number of electric appliances in forefinger and middle finger are stretched
one socket whose load is more than the maximum perpendicular to each other in such a way that
permitted limit. The two possible cause are forefinger indicates the direction of magnetic field,
a. all of a sudden supply of high voltage and middle finger indicate the direction of current
b. too many devices connected in a single socket. in the conductor then thumb will indicate the
direction of force on the conductor.
Precautions:
(b) The principle of electric motor is that when a
a. use of voltage regulator,
current carrying coil is placed in a magnetic field
b. load of a socket must be greater than its permitted
it experiences a torque and if the coil is allowed it
rating.
rotates in the magnetic field.
94. Write one difference between direct current and (c) Function of the parts of an electric motor :
alternating current. Which one of the two is mostly (1) Armature: Armature is a large number
produced at power stations in our country? Name one of turns of the coil on soft iron core which
device which provides alternating current. State one rotates in magnetic field.
important advantage of using alternating current. (2) Brushes: They allow current to pass from
external source to armature.
Ans : [CBSE 2012]
(3) Split rings: Split rings are of copper, splits into
Direct current has constant magnitude and two halves and make a connection between
unidirectional current. Alternating current changes its armature and brushes.
magnitude and direction alternatively.
a. Alternating current is produced in power stations 98. (a) Explain what is the difference between direct
in India. current and alternating current? Write one

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

important advantage of using alternating current. (ii) In bar magnet, magnetism is permanent but
(b) An air conditioner of 2 kW is used in an electric in solenoid it exists only till there is a current
circuit having a fuse of 10 A rating. If the potential in solenoid.
difference of the supply is 220 V, will the fuse
be able to withstand, when the air conditioner is
switched on? Justify your answer.
Ans : [CBSE 2016]
(a) Direct current is a unidirectional current with
constant magnitude. Alternating current is a
current which change its magnitude and direction
after a fixed period. AC voltage can be increased
or decreased. Where is dc voltage cannot be
increased or decreased. AC can be transmitted to
long distances with lesser power loss.
(b) Given P = 2 kW and V = 200 volt,
Power, P = VI & I = VP
I = 2000
220 = 9.09 A
The rating of the fuse wire is 10 A which is greater
than current drawn by air conditioner so when air
conditioner is switched on, fuse will not blow off.

99. (a) Describe an activity to show the pattern of

magnetic field fines of a bar magnet, with the help
of a cardboard piece and iron filings.
(b) Compare the field of a bar magnet with that of a
solenoid with the help of figure.
Ans : [CBSE 2016]
100. (a) Describe an activity to determine the direction
(a) Fix a white paper sheet on a drawing board with of magnetic field produced by a current carrying
the help of copper pins. Keep a bar magnet in the straight conductor. Also show that the direction
centre of the paper and sprinkle some iron filings of the magnetic field is reversed on reversing the
uniformly around the bar magnet. Tap the board direction of current.
gently. Iron filings arrange themselves in a pattern (b) An a -particle, (which is a positively charged
as shown in figure. These iron filings near the bar particle) benters, a uniform magnetic field at
magnet align themselves along the magnetic field right angles to it as shown below. Stating the
lines. relevant principle explain in which direction will
this a-particle moves?

Ans : [CBSE2016]
(a) Fix a cardboard and pass a straight wire through a
hole in cardboard and connect the two ends of the
(b) A current carrying solenoid behaves as a bar
wire with a cell through a rheostat and key with
magnet one end of the solenoid behaves like a N
a cell. Sprinkle iron filings uniformly on the card
pole and another end as S pole like two poles in
board. Pass the current in the wire and gently tap
bar magnet, so the field lines of a solenoid and bar
the card board. You would find that iron filings
magnet appear same in many ways:
align themselves in concentric circles around the
(i) Magnetic lines of force inside the body is
copper wire which represents the magnetic field
strong and uniform.
around the current carrying conductor. The
(ii) In both the cases stronger field exists at the
direction of magnetic field changes on reversing
poles compared to the middle part.
the direction of current.
Dissimilarities
(b) According to Fleming’s left hand rule the force on
(i) In bar magnet, the poles are not exactly at
the oc-particle will be inwards perpendicular to
the ends of the magnet, in solenoid poles can
the plane of paper, so \-particle will move in the
be considered to be lying at the edges.
direction of force.
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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

In both the cases of a current carrying solenoid and

bar magnet the magnetic lines of forces inside the
body is strong and uniform. In both the cases there
exists stronger magnetic field at the poles compared
to the middle parts.
Dissimilarities:
(i) The poles in a bar magnet do not exist at the
extreme ends of the magnet whereas in solenoid
the poles can be considered to be lying at the
edge.

101. Explain the meanings of the words “electromagnetic”

and “induction” in the term electromagnetic induction.
List three factors on which the value of induced current
produced in a circuit depends. Name and state the rule
used to determine the direction of induced current.
State one practical application of this phenomenon in
everyday life.
Ans : [CBSE 2014]
The word electromagnetic means that an electric
potential dipole is being produced in a coil due to (ii) In a bar magnet, magnetism is retained naturally,
change in magnetic field. The word induction means but in solenoid magnetism is there so long current
that the current has been induced. The value of flows through it.
induced current produced in a circuit depends on the
following factors: 103. (a) State the function of ‘a fuse’ in an electric circuit.
a. number of turns in given coil How is it connected in the domestic circuit?
b. area of each turn in coil (b) An electric fuse of rating 3A is connected in a
c. rate of change of magnetic field. circuit in which an electric iron of power 1.5 kilo
The rule is Fleming’s right hand rule. Stretch watt is connected which operates at 220 V. What
the thumb, forefinger and middle finger of right- would happen? Explain.
hand perpendicular to each other that forefinger Ans : [CBSE 2015]
indicates the direction of magnetic field, thumb gives (a) Fuse is a safety device to prevent the damage of
the direction of motion (or force) of the conductor, electrical devices from short circuit or overloading.
then middle finger will point the direction of induced A fuse is connected in series with the circuit.
current. (b) Given Power P = 1.5 kW = 1500 Watt and
Application: AC generator or DC generator. V = 220 Volts.
102. What is a solenoid? Sketch magnetic field lines Power P = VI & I = VP = 1500
220 = 6.8 A
produced around a current carrying solenoid. Mark The rating of fuse is 3A which is lesser the current
the region where field is uniform. Compare its field drawn by electric iron 6.8 A. So fuse wire will be
with that of a bar magnet. blown.
Ans : [CBSE 2015] 104. (a) Draw magnetic field lines of a bar magnet. “Two
A solenoid is a large number of insulated turns of the magnetic field lines never intersect each other”.
copper wire in the shape of helix (or cylinder). Why?
The patterns of the magnetic field lines around a (b) An electric oven of 1.5 kW is operated in a
current carrying solenoid is as given in figure. At the domestic circuit (220 V) that has a current rating
centre of the solenoid the magnetic field is uniform of 5 A. What result do you expect in this case?
and magnetic field lines are parallel. Explain.
Similarities: Ans : [CBSE 2014]

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

(a) Magnetic field lines around a bar magnet. 2- distance of the point from the wire \ I1
By decreasing current or increasing the distance
of the point from the wire, strength of magnetic
field also decreases.

107. (a) Name two electrical appliances of daily use in

which electric motor is used.
(b) Name and state the principle on which an electric
motor works.
Ans : [CBSE 2014]
(a) Drill machine, fan, grinder
(b) An electric motor works on the Fleming’s left
If the two magnetic field lines would intersect hand rule. When a current carrying coil is placed
with each other than at that point there will be in a magnetic field it experience a torque due to
two different directions of magnetic field which is which it rotates.
not possible. Fleming’s left hand rule-stretch left hand, thumb,
(b) Given Power P = 1.5 kW = 1500 Watt and forefinger and middle finger perpendicular to each
V = 220 Volts. other in such a way that forefinger indicates the
Current drawn I = ^P/V h = ^1500/220h A direction of magnetic field, middle finger indicates
the direction of current in the conductor then
I = 7 A (approx). thumb will point the direction of force on the
As the current drawn by the oven is 7 A which is conductor,
larger than the rating of the fuse (5A) so fuse will
blow off and circuit will be broken. 108. (a) What is an electromagnet? What does it consist
of?
105. (a) Explain any three properties of magnetic field (b) Name one material in each case which is used to
lines. make a : (i) permanent magnet (ii) temporary
(b) Give two uses of magnetic compass. magnet.
Ans : [CBSE 2014] (c) Describe an activity to show how you can make
(a) Properties of magnetic field lines: an electromagnet in your school laboratory.
1. Magnetic field lines emerge from N pole Ans : [CBSE 2006]
and merge at S pole outside a bar magnet a. A soft metal core made into a magnet by
and travel from S pole to N pole inside the the passage of electric current through a coil
magnet. surrounding it. It consists a soft iron core or its
2. These are continuous and closed curves. alloy and a solenoid conductor coil around the
3. Two field lines never intersect each other. core.
(b) Uses of magnetic compass : b. (i) To make a permanent magnet alloy Alnico
1. In navigation it is used to find direction. is used. (ii) Soft iron is used to make temporary
2. It is used to detect the magnetic field. magnet.
3. It can be used to test whether a substance is c. Take a long nail and put it into a solenoid of
magnetic or not. insulated copper wire. Pass the strong current in
106. (a) An electric current is passed in a horizontal copper
the solenoid the nail inside the solenoid becomes
wire from east to west. Explain your observations magnetised. This is called electromagnet.
when a compass needle is placed (i) below this 109. (a) Draw a schematic labelled diagram of a domestic
wire, (ii) above the wire. Draw inference from wiring circuit which includes (i) a main fuse (ii) a
your observations. power meter (iii) one light point and (iv) a power
(b) List the factors on which the strength of the plug.
magnetic field due to a straight conductor carrying (b) Why is it necessary to connect an earth wire to
current depend. How should these be changed to electric appliances having metallic covers?
decrease magnetic field at a point?
Ans : [CBSE 2005]
Ans : [CBSE 2014]
a.
(a) The direction of deflection of a magnetic compass
needle depends upon the direction of the magnetic
field at that point. The direction of the magnetic
field due to a current carrying wire is given by the
right hand screw rule. The direction of magnetic
field below and above the wire is opposite so
deflection in compass needle changes as well i.e,
the deflection is reverse direction.
(b) The factors affecting strength of the magnetic field
due to a straight wire carrying current:
1. magnitude of current in the wire \ I b. The earth wire carry current due to any leakage
or defective electric appliance to the earth keeping
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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

human beings safe preventing from any electric instruments? Why is it necessary to earth the
shock. metallic electric appliances?
(b) Explain what is short-circuiting and overloading
in an electric supply.
(c) What is the usual capacity of the fuse wire in the
line to feed:
(i) lights and fans?
(ii) appliances of 2 kW or more power?
Ans : [CBSE 2007]
(a) We can get an electric shock on touching a faulty
appliance, caused by the leakage of current from
the appliance. Earthing provides a safety measure
c. Properties of magnetic field lines against the electric shock caused by the leakage of
(i) They emerge from the north pole and merge current. Earth wire brings this leakage current to
at south pole of a bar magnet. the ground by a earth wire and we remains safe.
(ii) They do not intersect with each other. (b) Short circuiting takes place when a live wire and
(iii) They emerge and merge normal to the surface neutral wire come in contact with each other due
of magnet to damage of insulation of these wires. Due to
short circuiting, resistance of the circuit becomes
110. (a) What is meant by a ‘magnetic field’ ? minimum and a very high current is passed
(b) How is the direction of magnetic field at a point through the circuit which produces spark and
determined? heat and may lead a fire in the house. Overloading
(c) Describe an activity to demonstrate the direction when the amount of current flowing through the
of the magnetic field generated around a current circuit exceeds the rating of the protective devices
carrying conductor. it is said that circuit is overloaded. It is a situation
(d) What is the direction of magnetic field at the in which many electrical appliances are connected
centre of a current carrying circular loop? in a single socket. It will draw more current, may
Ans : [CBSE 2007] lead the burst of fire in building.
a. Magnetic field is the space around a magnet or a (c) (i) Bulbs, fans etc. – 5A, (ii) Heater – Micro-oven,
current carrying conductor in which its magnetic Electric iron – 15A
force can be experienced.
112. Describe in short an activity to:
b. A magnetic compass is used to demonstrate the
a. demonstrate the pattern of magnetic field lines
direction of the magnetic field generated around a
around a straight current carrying conductor, and
current carrying conductor.
b. find the direction of magnetic field produced for
c. Fix a cardboard and insert a wire to pass through
a given direction of current in the conductor.
its centre normal to the plane of the card board.
Name and state the rule to find the direction of
Sprinkle iron filings on card board uniformly. Pass
magnetic field associated with a current carrying
the current in the wire. Tap the cardboard gently.
conductor. Apply this rule to determine the
You will find that iron filings align themselves
direction of the magnetic field inside and outside
in the concentric circles around the wire. These
a current carrying circular loop lying horizontally
circles represents magnetic field lines around the
on a table. Assume that the current through the
conductor.
loop is anticlockwise.
d.
Ans : [CBSE 2010]
(a) Fix a cardboard and pass through its centre a
thick copper wire AB connected with a cell of
12 V through a rheostat, an ammeter and plug
key as shown in figure. Sprinkle the iron filings
uniformly on the cardboard. Plug in the key, tap
the cardboard gently a number of times. Iron
filings align themselves in a pattern of concentric
circles around the copper wire, which represents
the magnetic field lines.

At the centre of circular loop, the magnetic field

lines are straight.

111. (a) What is the function of an earth wire in electrical

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

(b)
(b) The direction of magnetic field so produced a. Name the type of current in two cases.
around a current carrying conductor can be find b. Identify any one source for each type of current.
with the help of a magnetic compass. When we c. What is the frequency of current in case (b) in
put a magnetic compass at any point of these field our country?
fines it get deflected. The direction of deflection d. On the basis of these graphs list two differences
of the compass needle is the direction of magnetic between the two currents.
field. e. Out of the two which one is used in transmitting
electric power over long distances and why?
Ans : [CBSE 2010]
a. (i) DC (ii) AC

If the direction of current is reversed the direction

of magnetic field is also reversed. The direction b. (i) cell, (b) AC generator
of magnetic field can be found by using Ampere’s c. 50 c/s or 50 Hz.
right hand thumb rule. According to it, if we d. (i) Magnitude of DC is constant magnitude of AC
hold a straight conductor in our right hand such is varying
that thumb points the direction of current in the (ii) DC is unidirectional ac changes its direction
conductor after a fixed period.
e. AC can be transmitted by changing it at high
113. In our daily life we use two types of electric current voltage with the help of transformer to minimise
whose current-time graphs are given below: loss in transmission.

114. (a) Describe an experiment with a diagram to

show that force is exerted on a current carrying
conductor when placed perpendicular in a
magnetic field.
(b) How will this force change if current in the
conductor is increased?
(c) Name a device that uses the above principle.
Ans : [CBSE 2010]
a. Take a small metal rod AB and suspend it from
a stand with the help of two connected wire. Put
(a) the rod in between the horse shoe magnet in such
a way that rod remains in between the two poles.
Pass the current in the rod through the two wires.
You would find that the rod is deflected towards
the left. Now reverse the direction of current the
rod is deflected in opposite direction. This shows
that a force is experienced by a current carrying
conductor in magnetic field.
b. If the current in the conductor is increased then
more force will act on the rod, and get more

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

deflected. entering first?

c. Electric motor. (ii) withdrawn from inside the coil?
(iii) held stationary inside the coil?
(b) Name the above phenomenon and mention the
name of the scientist who discovered it. State the
law that relates the direction of current in the coil
with the direction of motion of the magnet.
Ans : [CBSE 2011]
a. (i) Galvanometer gives a deflection
(ii) Again galvanometer gives a deflection but in
opposite direction.
(iii) No current is induced in the coil so no
deflection in the galvanometer.
b. Electromagnetic induction (EMI):
Faraday discovered it. Fleming’s right hand rule
gives the direction of induced current in the coil.
If we stretch right hand thumb, forefinger and
middle finger perpendicular to each other in such
115. (a) Which effect of the electric current is utilised in
a way that thumb gives the direction of motion
the working of an electrical fuse?
of the conductor, forefinger gives the direction
(b) A fuse is connected in series or in parallel in
of magnetic field then middle finger will give the
household circuit?
direction of current induced in the conductor.
(c) Draw a schematic labelled diagram of a domestic
circuit which has a provision of a main fuse, meter, 118. (a) When do we state that an electrical appliance is
one light bulb and a switch socket. earthed? Mention the function of earth wire in
Ans : [CBSE 2010] electric lines. Why is it necessary to earth the
a. Heating effect of current electric appliances having metallic body?
b. In series in the household circuit (b) Explain what is short circuiting and overloading
c. in an electric supply.
Ans :
(a) When metal body of an electric appliance is
connected to a wire which is connected to a metal
plate buried deep inside the earth is said to be
electrically earthed.
(b) If due to damaged insulation, live wire and neutral
wire come in contact with each other then it is
said to be short circuiting overloading. A circuit
over load occurs when the amount of current
flowing through the circuit exceeds the rating
116. Answer the following questions: of the protective device. Every electric circuit
a. What is the direction of magnetic field lines in a wiring system must be protected against
outside a bar-magnet? overloading. It happens when too many electric
b. Why two magnetic field lines cannot intersect appliances are connected into a single socket.
each other?
c. What is indicated by crowding of magnetic field 119. (a) Define electromagnetic induction.
lines in a given region? (b) Two coils P and S are wound over the same iron
d. What is the frequency of ac in India? core. Coil P is connected to battery and key
e. State one advantage of ac over dc. the coil S is connected to galvanometer. Draw a
Ans : [CBSE 2011] suitable diagram of this arrangement and write
your observations when:
a. From N pole to S pole (i) current in the coil P is started by closing the
b. If two magnetic field lines would intersect each key.
other then at the point of intersection there would (ii) current continues to flow in coil P.
be two different directions of magnetic field which (iii) current in coil P is stopped by removing the
is not possible. key.
c. Magnetic field strength is more in that region.
d. 50 cycles per sec (c/s) or Hz. Explain the reason for such observations.
e. AC can be step up for transmission over a longer Ans : [CBSE 2012]
distances with less power loss. a. The phenomenon by producing a current in a coil
by changing magnetic field associated with it or
117. (a) A coil of insulated copper wire is connected to a
by changing a current in the neighbouring coil
galvanometer. What will happen if a bar magnet
is called electromagnetic induction. Current so
is:
produced is called induced current.
(i) pushed into the coil with its north pole

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

b. (i) When key K is closed due to increasing current the circuit and justify your answer.
a magnetic field is produced which is changing.
In this changing magnetic field coils is kept so an
induced current flow through it, so galvanometer
shows a deflection.
(ii) After some time current reaches maximum
and becomes constant in P coil. There is
no change in current so there is no change
in magnetic field associated with coil S and (b) Give one difference between the wires used in the
hence no induced current in coil S. Deflection element of an electric heater and in a fuse.
in galvanometer becomes zero. (c) List two advantages of parallel connection over
series connection.
Ans : [CBSE 2012]
(a) Errors in the circuit
(i) Fuse wire is connected in neutral wire (N)
where as it must be connected in live wire
(L).
(ii) Circuit of bulb B2 is incomplete.
(b) Element of electric heater has high resistance and
high melting point whereas a fuse wire has high
(iii) Current becomes zero from maximum in coil resistance and low melting point.
P and hence galvanometer shows a deflection (c) Advantages of parallel connection over series
but now it is in opposite direction. connection.
(i) In parallel combination if one appliance fails
120. Two coils C1 and C2 are wrapped around a non- to work others keep working.
conducting cylinder. Coil C1 is connected to a battery (ii) Potential difference across each appliance
and key and C2 with galvanometer G. On pressing the remains same.
key (K), current starts flowing in the coil C1 State
122. (a) Write the values of the following physical quantities
your observation in the galvanometer.
in connection with domestic power supply in our
country: (i) potential difference between live wire
and neutral wire. (ii) frequency of ac.
(b) Explain the role of the following as safety measure
in domestic electric appliance/circuits: (i) earth
wire (ii) fuse.
Ans : [CBSE2012]
(a) (i) 220 V, (ii) 50 Hz
(b) Safety measure in electric appliance/circuits:
a. What key K is pressed on. (i) Earth wire is a safety device to protect us
b. When current in the coil C1 is switched off. from electric shock due to leakage of current
c. When the current is passed continuously through or faulty electric appliances. An earth wire
coil C1. is a thick copper wire connected to a metal
d. Name and state the phenomenon responsible for plate buried deep in the earth. The metallic
the above observation. Write the name of the rule body of the electric appliance is connected to
that is used to determine the direction of current the earth wire, it provides a low resistance
produced in the phenomena. conducting path and leaked current goes to
deep in the earth and human beings do not
Ans : [CBSE 2012,14]
get a fatal electric shock.
a. Induced current in coil C2 is produced so (ii) Fuse: It is also a safety device. It is a wire of
galvanometer shows a deflection. an alloy with low melting point. If a current
b. Again galvanometer shows a deflection but in greater than a particular values flows in the
opposite direction to the previous one. circuit it will melt and circuit is broken and
c. There will be no deflection in galvanometer. stops power supply in the circuit.
d. This phenomenon is called electromagnetic
induction. The phenomenon in which a changing 123. What is a solenoid? Draw the magnetic line of forces
magnetic field in a coil induces a current in another for solenoid and a bar magnet. Compare the two and
coil kept near it. Fleming’s right hand rule is used state one similarity.
to find the direction of induced current. Ans : [CBSE2013]

121. (a) The given figure shows a domestic electric circuit. A solenoid is a large number of turns of insulated
Study this circuit carefully. List any two errors in copper wires having shape of a cylinder or helix.
Magnetic field are given in following figures.

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Chap 13 : Magnetice Effect of Electric Current www.cbse.online

(a) Fix a white paper sheet on a drawing board with

the help of copper pins. Keep a bar magnet in the WWW.CBSE.ONLINE

centre of the paper and sprinkle some iron filings WWW.CBSE.ONLINE

uniformly around the bar magnet. Tap the board
gently. Iron filings arrange themselves in a pattern NO NEED TO PURCHASE ANY BOOKS
as shown in figure. These iron filings near the bar For session 2019-2020 free pdf will be available at
magnet align themselves along the magnetic field www.cbse.online for
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(b) A current carrying solenoid behaves as a bar

magnet one end of the solenoid behaves like a N
pole and another end as S pole like two poles in
bar magnet, so the field lines of a solenoid and bar
magnet appear same in many ways:
(i) Magnetic lines of force inside the body is
strong and uniform.
(ii) In both the cases stronger field exists at the
poles compared to the middle part.
Dissimilarities
(i) In bar magnet, the poles are not exactly at
the ends of the magnet, in solenoid poles can
be considered to be lying at the edges.
(ii) In bar magnet, magnetism is permanent but
in solenoid it exists only till there is a current
in solenoid.

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