FOUNDATIONScience 10th pdf

SARWAR CLASSES CLASS- X FOUNDATION (IIT/PMT)
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H.O:-VENUSTOWER,CIVILLINES,MEDICALROAD,ALIGARH.9219418880,B. O:-RAMGHAT ROAD. OPPOSITE OLF SCHOOL, ABOVE OBC.9219694458
1. LIGHT – REFLECTION AND REFRACTION
Light:
(i) It is an invisible energy, which causes the sensation of sight.
(ii) It is the form of energy, which gives in us a sensation of sight. It, itself is not visible
but helps us in seeing objects.
Laws of Reflection:
(i) Angle of incidence is equal to the angle of reflection. ( i =  r)
(ii) The incident ray, the reflected ray and the normal at the point of incidence, all lie in
the same plane.
Laws of refraction:
(I)The ratio of sine of the angle of incidence to the sine of the angle of refraction for a
particular pair of media is constant, i.e.,
r
i
sin
sin
= constant = . This is also called
Refractive Index and also denoted by n.
(ii) The incident ray, the refracted ray and the normal at the point of incidence all lie in
the same plane.
Refraction through prism: When light passes through a prism
(i) It always bends towards the base of the prism.
(ii) A prism splits the light passing through it into its corresponding wavelengths. This
process is called dispersion of light. When sunlight passes through prism it
disperses into seven colours, i.e., seven wavelengths (VIBGYOR).
Cartesian sign convention
In the case of concave mirror for real
and inverted image
Focal length (f) = –ve
Radius of curvature (R) = –ve
Object distance (u) = –ve
Object height (h) = +ve
Image distance (v) = –ve
Image height (h) = –ve
Magnification (m) = –ve
In the case of concave mirror for
virtual and erect image
focal length (f) = –ve
Radius of curvature (R) = –ve
Image distance (v) = +ve
Image height (h) = +ve
Magnification (m) = +ve
In case of convex mirror for virtual
and erect image :
Focal length (f) = +ve
Radius of curvature (R) = +ve
SPHERICAL MIRRORS

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IMAGE FORMATION BY A CONCAVE MIRROR FOR DIFFERENT POSITIONS OF
THE OBJECT
Position of the object Position of the image Size of the image Nature of the image
At infinity At the focus F Highly diminished, point
sized
Real and inverted
Beyond the centre of
curvature C
Between F and C Diminished Real and inverted
At C At C Same size Real and inverted
Between C and F Beyond C Enlarged Real and inverted
At F At infinity Infinitely large or highly
enlarged
Real and inverted
Between the pole P of the
mirror and focus F
Behind the mirror Enlarged Virtual and erect
IMAGE FORMATION BY A CONVEX MIRROR
At infinity At the focus F, behind the
mirror
Highly diminished
point-sized
Virtual and erect
Between infinity and the
pole P of the mirror
Between P and F, behind the
mirror
Diminished Virtual and erect
The corresponding ray diagrams are included in annexure 4
Mirror Formula :
uvf
111
 is called the mirror formula.
Magnification: The ratio of the size of the image to that of the object is called
magnification. For a mirror, magnification (m) is given by.
u
v
m


LENSES
Lens: A piece of any transparent material bound by two curved surfaces is called a lens. A
lens which is thicker in the middle and thinner at the edges is called a convex lens. A
convex lens is also called converging lens.
A lens which is thicker at the edges and thinner at the centre is called a concave lens. A
concave lens is called a diverging lens.
Optical center of a lens: The centre point of a lens is called its optical center. A ray of
light passing through the optical center does not suffer any deviation.

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Power of a lens: Reciprocal of the focal length of a lens measured in meters is called the
power. Power of a lens is described in dioptre (D) units.
Images formed by a lens: A convex lens forms a real and inverted image for all the
positions of an object outside its focus (F). However, when the object is placed between F
and O, the image formed by a convex lens is virtual and erect.
A concave lens always forms a virtual, erect and a diminished image, whatever may be the
distance of the object from the lens.
Lens formula:
uvf
111

Magnification: m =
u
v
Cartesian sign convention
In case of convex lens for real and
inverted image
Focal length (f ) = +ve
Image height (h) = –ve
Magnification (m) = –ve
In case of convex lens for virtual and
erect image
Focal length (f ) = +ve
In case of concave lens For
virtual and erect image
Focal length(f ) = –ve
IMAGE FORMATION BY A CONCAVE LENS
At infinity At focus F1 point-sized Highly diminished Virtual and erect
Between infinity and optical
centre O of the lenses
Between focus F1 and
optical centre
Diminished Virtual and erect

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IMAGE FORMED BY A CONVEX LENS FOR DIFFERENT POSITIONS OF THE
OBJECT
At infinity At focus F2 Highly diminished,
point-sized
Real and inverted
Beyond 2F1 Between F2 and 2F2 Diminished Real and inverted
At 2F1 At 2F1 Same size Real and inverted
Between F1 and 2F1 Beyond 2F2 Enlarged Real and inverted
At focus F1 At infinity Infinitely large or highly
enlarged
Real and inverted
Between focus F1 and
optical centre O
On the same side of the lens
as the object
Enlarged Virtual and erect
The corresponding ray diagrams are included in annexure 4
IMPORTANT FORMULAE
Mirror formula
uvf
111

where, f = focal length of mirror, u = Distance of the object, v = Distance of the image
from pole.
Lens formula
uvf
111

where, f = focal length of the lens, v = Distance of the image, u = Distance of the object
from optical centre.
Power of lens
cm)(inlengthFocal
100
meters)(inlengthFocal
1
P
)(
100
)(
1
cmfmf
P 
Magnification by a lens =
objecttheofsize
imagetheofsize
o
i
h
h
m 

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Magnification by a lens =
u
v
m or
centreopticalthefromobjecttheofDistance
centreopticalthefromimagetheofDistance
REFRACTIVE INDEX
 Absolute refractive index (n) of a medium is the ratio of speed of light in vacuum or air
(c) to the speed of light in the medium (v) i.e.
v
c
n 
 Refraction of light is the phenomenon of change in the path of light in going from one
medium to another.
 In going from a rarer to a denser medium, the ray of light bends towards normal and in
going from a denser to a rarer medium, the ray of light bends away from normal.
 Snell’s law of refraction: 2
1
1
2
sin
sin
n
n
n
r
i

 No refraction occurs, when
(i) light is incident normally on a boundary,
(ii) refractive indices of the two media in contact are equal.
 Refractive index = 21n =
1mediumofindexrefractive
2mediumofindexrefractive
2mediuminlightofspeed
1mediuminlightofspeed


31
21
23




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MIND MAP
 Light is a form of energy that produces in us
the sensation of sight.
 Reflection of light is the phenomenon of
bouncing back of light in the same medium
on striking the surface of any object.
 The two laws of reflection are :
(i) the incident ray, the reflected ray and the
normal (at the point of incidence), all lie in
the same plane.
(ii) the angle of reflection (r) is always equal
to the angle of incidence (i)
r = i
 Mirror formula:
fuv
111

 Linear magnification produced by a spherical
mirror is
)(objectofsize
)(imageofsize
1
2
h
h
u
v
m 


 For a convex mirror, m is +ve and less than
one, as the image formed is virtual, erect and
shorter than the object.
 Absolute refractive index(n) of a medium is
the ratio of speed of light in vacuum or air(c)
to the speed of light in the medium(v) i.e.
v
c
n 
 Refraction of light is the phenomenon of
change in the path of light in going from one
medium to another.
 In going from a rarer to a denser medium,
the ray of light bends towards normal and in
going from a denser to a rarer medium, the
ray of light bends away from normal.
 Snell’s law of refraction,
2
1
1
2
sin
sin
n
n
n
r
i

 No refraction occurs, when
 Lens formula :
fuv
111

 New Cartesian Sign Convention for spherical
lenses:
(i) All distances are measured from optical
centre C of the lens.
(ii) The distances measured in the direction
of incidence of light are taken as positive and
vice-versa.
(iii) All heights above the principal axis of the
lens are taken as positive and vice versa.
 The linear magnification produced by a lens
 According to New Cartesian Sign Convention, for spherical mirror.
(i) All distances are measured from the pole of the spherical mirror.
(ii) The distances measured in the direction of incidence of light are taken as positive and vice-versa.
(iii) The heights above the principal axis of the mirror are taken as positive and vice-versa.
LIGHT–REFLECTIONANDREFRACTION

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EXERCISE – I
1. A ray of light goes from water into air. Will it bend towards the normal or away from
normal?
2. Two thin lenses of powers P1 and P2 are placed in contact. What is the power of
combination?
3. A boy is standing 4 m away from a plane mirror. What is the distance between the boy
and his image?
4. Define refractive index of a medium in terms of speed of light. If the speed of light in
water is 2.25  108
m/s and that in vacuum be 3  108
m/s, calculate the refractive index
of water.
5. The refractive index of one type of glass is 1.50. If the speed of light in vacuum be 3 
108
ms–1
, calculate the speed of light in this glass.
6. A small object is so placed in front of a convex lens of 5 cm focal length that a virtual
image is formed at a distance of 25 cm. Find the magnification.
7. Refractive index for dense flint glass ,65.1)( fa refractive index for alcohol
36.1)( ala with respect to air. Find the refractive index of flint glass with respect to
alcohol )( fa  .
8. How will you distinguish between a plane mirror, a concave mirror and a convex mirror
without touching them? Explain.
9. A Convex mirror used in an automobile has 3.00 m radius of curvature. If a bus is located
at 5.00 m from this mirror, find the position, nature and size of the image.
10. Define (i) principal focus, and (ii) focal length, of a convex mirror with the help of a
labelled diagram.
11. An object 3 cm high is placed at a distance of 8 cm from a concave mirror which
produces a virtual image 4.5 cm high.
(i) What is the position of the image?
(ii) What is the focal length of the mirror?

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12. An object placed 20 cm in front of a mirror is found to have an image 15 cm (a) in front
of it, (b) behind the mirror. Find the focal length of the mirror and the kind of mirror in
each case.
13. A man of height 180 cm is standing in front of a plane mirror. His eyes are at a height of
170cm from the floor. What should be the minimum length of the plane mirror for the
man to see his full length image?
14. A plane mirror is moved towards a stationary observer with a speed of 3 m/s. With what
speed will his image move towards him?
15. A wall clock has numericals instead of marks. What time will its image in a plane mirror
show if the actual time seen directly in the clock is 05 : 28 : 37?
EXERCISE – II
1. A convex lens forms a real and inverted image of a needle at a distance of 50 cm from the
lens. If the image is of the same size as the needle, where is the needle placed in front of
the lens? Also find the power of the lens.
2. Calculate the focal length of a convex lens which produces a virtual image at a distance
of 50 cm of an object placed a 20 cm in front of it.
3. An object 60 cm from a lens gives a virtual image at a distance of 20 cm in front of the
lens. What is the focal length of the lens? Is the lens converging or diverging? Give
reasons for your answer.
4. For an object placed at a distance of 20 cm from the pole of a mirror, an image is formed
40 cm further away from the object on the same side.
(a) What is the nature of the mirror?
(b) Is the image formed real or virtual?
(c) Draw a ray diagram to show the image formed.
(d) Calculate the focal length of the mirror used.
5. A concave mirror produces three times magnified real image of an object placed at 10 cm
in front of it. Where is the image located?
6. At what distance from a concave mirror of focal length 10 cm should an object 2 cm long
be placed so as to get erect image 6 cm tall?

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7. An object is placed at a distance of 10 cm from a convex mirror of focal length 15 cm.
Find the position and nature of the image.
8. What is refraction of light? Explain with the help of a labelled diagram.
9. State and explain the laws of refraction of light.
10. State the effects produced by the refraction of light which can be easily observed in our
day to day life.
11. An object is 2 m from a lens which forms an erect image exactly one-fourth the size of
the object. Determine the focal length of the lens. What type of lens is this?
12. State and explain the laws of reflection of light with the help of a labelled diagram.
13. Describe with the help of a labelled ray-diagram, the nature, size and position of the
image formed when an object is placed anywhere between the pole and infinity in front
of a convex mirror.
14. Describe with the help of a ray-diagram the nature, size and position of the image formed
when an object is placed in front of a convex lens between optical centre and focus. State
three characteristics of the image formed.
15. What happens when a parallel beam of light rays falls on a concave lens? Explain with
the help of a labelled diagram. Also define principal focus and focal length of a concave
lens and mark them on the diagram.
EXERCISE – III
1 An object is placed at a distance of 30 cm from a concave mirror of focal length 20 cm.
Where will the image be formed?
2. A 2.0 cm high object is placed perpendicular to the principal axis of a concave mirror.
The distance of the object from the mirror is 30 cm, and its image is formed 60 cm from
the mirror, on the same side of the mirror as the object. Find the height of the image
formed.
3. A 2.0 cm high object is placed at a distance of 20 cm from a concave mirror. A real
image is formed at 40 cm from the mirror. Calculate the focal length of the mirror and the
size of the image.

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4. Find the position, size and the nature of the image formed by a spherical mirror from the
following data:
u = –20 cm, f = –15 cm, h0 = 1.0 cm
5. A concave mirror forms an erect image of an object placed at a distance of 10 cm from it.
The size of the image is double that of the object. Where is the image formed?
6. An object is placed 30 cm from a convex lens. A real image is formed 20 cm from the
lens. Find the focal length of the lens.
7. A 2.0 cm long pin is placed perpendicular to the principal axis of a convex lens of focal
length 12 cm. The distance of the pin from the lens is 15 cm. Find the size of the image.
8. A point object is placed at a distance of 12 cm from a convex lens on its principal axis.
Its image is formed on the other side of the lens at a distance of 18 cm from the lens. Find
the focal length of the lens.
9. An object is placed on the principal axis of a concave lens at a distance of 20 cm from it.
If the focal length of the lens is also 20 cm, find the location of the image.
10. A pin which is 2 cm long is placed at a distance of 16 cm from a convex lens. Assuming
it is to be perpendicular to the principal axis, find the position, size and the nature of the
image if the focal length of the lens is 12 cm.
11. A 4.0 cm high object is placed at a distance of 60 cm from a concave lens of focal length
20 cm. Find the size of the image.
12. Describe with the help of a ray-diagram, the size, nature and position of the image
formed by a convex lens when an object is placed beyond 2f in front of the lens.
13. How far should an object be held from a concave mirror of focal length 40 cm so as to
obtain a virtual image twice the size of the object?
14. A glass slab of thickness 6 cm contains the same number of waves as 10 cm thick water
layer when the same monochromatic beam of light is allowed to incident on them. If the
absolute value of refractive index of water is
3
4
, what will be absolute value of refractive
index of glass?
15. An object of height 5 cm is placed 10 cm from a convex mirror of radius of curvature
30cm. What is the nature and size of the image?

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2. HUMAN EYE AND COLOURFUL WORLD
• The ability of the eye to focus both near and distant objects by adjusting its focal length is
called the power of accommodation of the eye.
• The smallest distance at which the eye can see objects clearly without strain, is called the
near point of the eye or the least distance of distinct vision. It is 25 cm for a normal eye.
• The farthest point upto which the eye can see objects clearly is called the far point of the
eye. It is infinity for a normal eye.
• The splitting of white light into its component colours is called dispersion.
• The scattering of light by the colloidal particles of a medium due to which the path of the
light becomes visible is known as Tyndall Effect.
• There are three common refractive defects of vision.
 Myopia or short sightedness.
 Hypermetropia or long sightedness.
 Presbyopia.
MYOPIA OR SHORT-SIGHTEDNESS
• A person with myopia can see nearby objects clearly but cannot see distant objects
distinctly.
Causes of Defect: The two possible causes of this defect are:
(a) Excessive curvature of the eye lens or due to the high converging power of eye lens
(short focal length).
(b) Elongation of the eyeball.
Corrective Measures: This defect can be corrected by using spectacles with concave
lens of suitable focal length or power.
HYPERMETROPIA OR LONG-SIGHTEDNESS
• A person with hypermetropia can see distant objects clearly but cannot see nearby objects
distinctly.
Causes of Defect: The two possible causes of this defect are:

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(i) Low converging power of eye lens because of large focal length.
(ii) Eye-ball being too short.
Corrective Measures: This defect can be corrected by using spectacles with convex lens
of suitable focal length or power.
PRESBYOPIA OR OLD SIGHT
• Presbyopia is due to decrease in power of accommodation with ageing.
Cause of Defect: Presbyopia arises due to the gradual weakening of the ciliary muscles
and diminishing flexibility of the eye lens with age.
Presbyopia is the hypermetropia caused by the loss of power of accommodation of the
eye due to old age.
Corrective Measures: Presbyopia defect is corrected in the same way as hypermetropia
i.e. by using spectacles having convex lenses. Sometimes when far vision is also affected
bifocal lenses are used.
ATMOSPHERIC REFRACTION
It can be defined as bending of light while going through various layers of air in the
atmosphere.
 Twinkling of stars: They are point source of light and atmospheric refraction causes
bending of light. Apparent image is higher than actual image and causes twinkling effect.
 Planets do not twinkle, as they are not point source of light.
 Early sunrise and late sunset: Sun can be seen two minutes before actual sunrise and
two minutes after sunset due to atmospheric refraction.
SCATTERING OF LIGHT

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 Sun appears reddish at sunrise and sunset due to, lower wavelengths (blue) getting
scatteredand higher wavelength (red) reaching us.
 Sky appears blue to us due to scattering of lower wavelengths (blue).
 To an astronaut sky appears dark as there is no atmosphere, thus no scattering.
Sun nearly
overhead
Less blue
scattered
Observer
Sun near
horizon
Blue scattered away,
Sun appears reddish

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MIND MAP
HUMANEYEANDCOLOURFULWORLD
The ability of an eye to focus both near and
distant objects by adjusting its focal length is
called the power of accomodation of an eye.
The smallest distance at which an eye can see
objects clearly without strain, is called the near
point of an eye or the least distance of distinct
vision. It is 25 cm for a normal eye.
The farthest point upto which an eye can see
objects clearly is called the far point of an eye. It
is infinity for a normal eye.
The splitting of white light into its component
colours is called dispersion.
The scattering of light by the collidal particles of
a medium due to which the path of the light
becomes visible is known as Tyndall Effect.
Scattering of light causes the blue colour of the
sky, reddening of the sun at sunrise and sunset.
There are three common refractive defects of
vision.
 Myopia or near sightedness.
 Hypermetropia or long sightedness.
A person with myopia can see nearby objects
clearly but cannot see distant objects distinctly.
The defect can be corrected by using concave
lens of suitable focal length.
A person with hypermetropia can see distant
objects clearly but cannot see near by objects
distinctly.
The defect can be corrected by using convex lens
Presbyopia is due to decrease in power of
accommodation with ageing.
The defect can be corrected by using bifocal

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EXERCISE – I
1. What is the least distance of distinct vision of a normal human eye?
2. Define power of accommodation.
3. Name the muscles responsible for bringing change in the focal length of the eye.
4. What is the far point of a normal human eye?
5. What is the near point of a normal human eye?
6. What is the type of lens used for correcting myopia?
7. What type of lens is used for correcting hypermetropia?
8. Which defect of eye can be corrected by using cylindrical lens?
9. Name the type of lens which is used for correcting the presbyopia?
10. What is cataract?
11. What is angle of prism?
12. What do you mean by angle of deviation in prism?
13. What do you mean by dispersion of light?
14. Name a natural spectrum.
15. What do you mean by atmospheric refraction of light?

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EXERCISE – II
1. What do you mean by scattering of light or Tyndall effect?
2. Why are the danger signal lights red in colour?
3. Why does the sky appear dark instead of blue to an astronaut?
4. What happens to the image distance in the eye when we increase the distance of an object
from the eye?
5. What is colour blindness?
6. What is presbyopia?
7. A chicken can see only in the bright light. What type of cells are present in retina?
8. What is persistence of eye vision?
9. What is meant by power of accommodation of the eye?
10. How do we see colours?
EXERCISE – III
1. Draw a leveled diagram of human eye.
2. What is long sightedness or hypermetropia? What causes long sightedness and how is it
corrected?
3. What is short sightedness or myopia? What causes short sightedness and how is it
corrected?
4. Why do the colour of the sun appears red as sun rise and sun set?

17
5. The far point of a myopic person is 80 cm in front of the eye. What is the power of the
lens required to enable him to see the distant objects clearly?
6. A person with a defective eye-vision is unable to see the objects nearer than 1.5 m. He
wants to read books at a distance of 30 cm. Find the nature, focal length and power of the
lens he needs in his spectacles.
7. For point of a myopic person is 40 cm. What type of lens should be wear so as to see the
distant object clearly? Calculate the focal length and the power of the lens he should use.
8. A myopic person has been using spectacles of power –1.00 D for clear vision. During old
age he also needs to use separate reading glasses of power +2.00 D. Explain what may
have happened to his eye-sight?
9. Why do the stars twinkle?
10. Why does the colour of the sky appear blue?

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3. ELECTRICITY
Electricity and its Effect (notations)
Physical Quantity Symbols SI unit
Voltage (potential difference) V Volt (V)
Power P Watt (W)
Charge Q Coulomb (C)
Work or Energy W Joule (J)
Resistance R Ohm ()
Current I Ampere (A)
Resistivity  Ohm metre ( m)
Laws of electric forces:
(i) Like charges repel and unlike charges attract each other.
(ii) Charges of a conductor reside on its outer surface.
Current:
The rate of flow of charges (Q) through a conductor is called current (I) and is given by.
Current =
Time
charge
or
t
Q
I  . The SI unit of current is ampere (A).
1 Ampere
second1
coulomb1

The current flowing through a circuit is measured by a device called ammeter. Ammeter
is connected in series with the conductor. The direction of the current is taken as the
direction of the flow of positive charge and opposite to the flow of electrons through the
conductor.
Electric cell: It is the simplest form of arrangement to maintain a constant potential
difference between two points.
Electromotive force: The potential difference at the terminals of cells in an open circuit
is called electromotive force (emf) and is denoted by letter E.

19
Potential difference is the work done in bringing a unit charge from one place to another.
charge
work
DifferencePotential  ,
(C)Coulomb1
)(JJoule1
(V)Volt1 
Ohms law: At any constant temperature the current (I) flowing through a conductor is directly
proportional to the potential difference (V) across it. Mathematically,
I  V vice-versa V  I
or V = RI 
R
V
I
I
V
R  ,
where R – Resistance, V – Voltage (P.D.), I – Current
Symbols of a few commonly used components in Circuit Diagrams
Component Symbol Component Symbol
An electric cell Electric bulb
Battery of cells A resistance
Plug key or switch
(open)
or
Variable resistance
(Rheostat)
or
A closed plug or
switch
or Ammeter A+ –
A wire joint Voltmeter V+ –
Wires crossing Galvanometer G+ –
Resistance: Resistance is a property of a conductor by virtue of which it opposes the flow of
electricity through it. Resistance is measured in Ohms (). Resistance is a scalar quantity.
Conductor: Low-resistance material which allows the flow of electric current through it is
called a conductor. All metals are conductors except Hg and Pb etc.
Resistor: High-resistance materials are called resistors. Resistors become hot when current flows
through them (nichrome wire is a typical resistor).

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Insulator: A material which does not allow heat and electricity to pass through it is called an
insulator. Rubber, dry wood etc., are insulators.
Equivalent Resistance: A single resistance which can replace a combination of resistances such
that current through the circuit remains the same is called equivalent resistance.
Law of Combination of Resistances in Series: When number of resistances are connected in
series, the equivalent resistance is equal to the sum of the individual resistances.
321 VVVV 
332211 ,,, IRVIRVIRVIRV 
321 IRIRIRIR 
nRRRRR  .....321
Law of Combination of Resistances in Parallel: If resistance .....,,, 321 RRR etc are connected
in parallel then the equivalent resistance (R) is given by
321 IIII 
3
3
2
2
1
1 ,,,
R
V
I
R
V
I
R
V
I
R
V
I 
321 R
V
R
V
R
V
R
V

nRRRRR
1
.....
1111
321


21
Electrical energy: Capacity of the flowing electricity to do work is called its electrical energy.
Electrical energy (work) =
R
tV
PtRtItIV
2
2

The SI unit of electrical energy is Joule. One Joule is the amount of energy consumed when an
electrical appliance of one watt rating is used for one second. The commercial (practical) unit of
electrical energy is kilowatt-hour (kWh).
Power,
R
V
RIVI
t
W
P
2
2

The SI unit of electric power is watt (W). The power of a machine doing work at the rate of 1
Joule per second is equal to one watt.
Electrical energy = Electrical power × Time.
Important Formulae:
1. Coulomb’s law
2
21
r
qqK
F

 (k is constant of proportionality)
1q and 2q = two electric charges
r = distance between two electric charges
F = Force
2.
V
W
QQVW
Q
W
V  ;;
..dpV  W = work done, Q = Quantity of charge transferred
3.
R
V
I
I
V
RIRV  ;;

22
V = pd ; R = Resistance, I = current.
4.
l
AR
A
I
R



 ;
R = Resistance; l = length; A = Area of cross section;  = rho, a constant known as
resistivity
5. Series combination nRRRRR  .....321
6. Parallel combination
nRRRRR
1
.....
1111
321
 For equal resistances
nRRs  (For series connection)
n
R
Rp  (For parallel connection)
2
n
Rp
Rs

Rs = Effective resistance in series
Rp = Effective resistance in parallel
n = number of resistors
R = Resistance of each resistor
7.
Time
consumedEnergy
time
work
Power; 
t
W
P
8. W = V × I × t ; Power = potential difference × current × time
 )( 2
RtIW   








R
tV
W
2
9. P = V × I ; Power = potential difference × current
10. RIP  2
; Power = resistance(current)2

11.
R
V
P
2
 ;
resistance
)difference(potential
Power
2

12. Electric energy = P × t ; electric energy = power × time

23
MIND MAP
Formulae
t
Q
I 
Q
W
V 
IRV  (ohm’s law)
A
R


.......321 RRRR 
(Series connection)
321 R
I
R
I
R
I
R
I

(Parallel connection)
RTIH 2

R
V
RIVIP
2
2

VItWE 
I – Current
Q – Charge
t – Time
V – Potential difference
p – Resistivity
Ammeter
 Measures electric current.
 Has low resistance.
 Connected in series.
Voltmeter
 Measures potential difference.
 Has high resistance.
S.I. Units
Current – Ampere (A)
Resistance – Ohm ()
Potential Difference – Volt (V)
Power – Watt (W)
Electric Energy – Kilo Watt Hour (kWh)
Resistivity – Ohm-meter (m)
Electric Current
The amount of charge flowing through a particular area per unit time in a conductor.
ELECTRICITY
Conversions
1 watt =
second1
Joule1
1 KW = 1000 W
1 KJ = 1000 J
1 Horse Power = 746 W
1 Ohm =
ampere1
volt1
1 KWh = 3.6 x 10
6
J
1 Ampere =
second1
coulomb1

24
EXERCISE – I
Q. 1 – 3 are of one mark each.
Q. 4 – 7 are of two or three marks each.
Q. 8 is of five marks.
1. State the relation between potential difference, work done and the charge moved.
2. Define 1 ampere.
3. By what name is the physical quantity coulomb/second known as?
4. What will be the current drawn by an electric bulb of 40 W when it is connected to a
source of 220 V?
5. What will be the resistance of a metal wire of length 2 meters and area of cross section
1.55 × 10–6
m2
if the resistivity of the metal be 2.8 × 10–8
m.
6. Keeping the potential difference constant, the resistance of a circuit is doubled. By how
much does the current change?
7. An electric bulb draws a current of 0.25 A for 20 minutes. Calculate the amount of
electric charge that flows through the circuit.
8. A potential difference of 250 volts is applied across a resistance of 500 ohms in an
electric iron. Calculate
(a) Current
(b) Heat energy produced in Joules in 10 seconds

25
EXERCISE – II
MULTIPLE CHOICE QUESTIONS
1. When a body is negatively charged by friction it means
(a) the body has acquired excess of electrons
(b) the body has acquired excess of protons
(c) the body has lost some electrons
(d) the body has lost some protons
2. There is no flow of current between two charged bodies when connected because
(a) they have the same quantity of charge
(b) they have the same potential
(c) they have the same capacity
(d) they have the same ratio of potential per unit charge
3. Electromotive force represents
(a) force (b) energy
(c) energy per unit charge (d) current
4. The unit of e.m.f. of a cell is
(a) dyne (b) volt
(c) ampere (d) joule
5. The commonly used safety fuse wire is made of
(a) copper (b) lead
(c) nickel (d) an alloy of tin and lead
6. Kilowatt hour is the unit of
(a) power (b) energy
(c) impulse (d) force

26
7. 1 KWh is equal to
(a) MJ106.3 6
 (b) MJ106.3 3

(c) MJ106.3 2
 (d) 3.6 MJ
8. A man has five resistors each of value 
5
1
. What is the maximum resistance he can
obtain by connecting them?
(a) 1 (b) 5
(c)
2
1
 (d)
5
2

9. What is the minimum resistance that one can obtain by connecting all the five resistance
given in the last question
(a) 
10
1
(b) 
5
1
(c) 
50
1
(d) 
25
1
10. Conventionally the direction of the current is taken as
(a) the direction of flow of negative charge (b) the direction of flow of molecules
(c) the direction of flow of atoms (d) the direction of flow of positive charge
11. How will the reading in the ammeter A (Figure) be
affected if another identical bulb Q is connected in parallel
to P? The voltage in the mains is maintained at a constant
value
(a) the reading will be reduced to one-half
(b) the reading will not be affected
(c) the reading will be double the previous value
(d) the reading will be increased four fold
P


Mains Q
Switch
A
12. The unit of resistivity is
(a) ohm (b) ohm
(c) ohm-metre (d) ohm per metre

27
13. If the length of a wire is doubled and its cross-section is also doubled then the resistance
will
(a) increase eight times (b) decrease four times
(c) become four times (d) remain uncharged
14. In the circuit shown below, the reading of the voltmeter V
will be
(a) 4V (b) 2V
(c) 6V (d) 3V
12 V
V
200100
 +
15. In the figure distance (d) between conductors carrying current 1I
and 2I is varied
Which of the following graphs correctly represent the variation
between force (F) between the conductors and distance (d)?
I1 I2
d
(a) F
d
(b) F
d
(c) F
d
(d) F
d
16. 1 Volt equals
(a) 1 joule (b) 1 joule per coulomb
(c) 1 coulomb per metre (d) 1 Newton per coulomb

28
17. Which of the following networks yields maximum effective resistance between A and B?
(a) 2 

2 
2  BA
(b)
2
2 2
A B
(c) 2 
2 A 2  B
(d)
A B
2 
2 
2 
18. What is the resistance between A and B in the given network.
(a) 2 (b) 4
(c)
2
3
 (d)
3
2

2
1 1
2
A B
19. Good conductors have many loosely bound
(a) atoms (b) molecules
(c) protons (d) electrons
20. One ampere equals
(a) A106
 (b) A10 6

(c) A10 3

(d) 10 A
21. How many electrons constitute a current of one microampere?
(a) 6
1025.6  (b) 12
1025.6 
(c) 9
1025.6  (d) 15
1025.6 

29
22. The equivalent resistance between P and Q will be
(a) 7 (b) 2
(c)
5
3
 (d) 1
22
1
P
Q
2
23. If a wire of resistance 1 is stretched to double its length, then its resistance will become
(a)
2
1
 (b) 2
(c)
4
1
 (d) 4
24. Which switch in the circuit when closed will produce short
circuiting?
(a) A (b) B
(c) C (d) none of the
above
A
B
Resistance
Lamp
C
25. Seven identical lamps of resistance 2200  each are
connected to a 220 V line as shown below. Then the
reading in the ammeter will be
(a) A
10
1
(b) A
5
2
220V
(c) A
10
3
(d) none of these
26. What is the resistance between A and B in the
following circuit?
(a) 1 (b) 2
(c)
2
1
 (d)
2
3
 A B
2
2
2
2
1
1
1 1
1

30
27. The fact that current is associated with a magnetic field was discovered by
(a) Oersted (b) Maxwell
(c) Faraday (d) Ohm
28. What is the resistance between P and Q?
(a)
4
3
 (b)
3
4

(c)
3
16
 (d) infinity
 P Q
2 2
2
22
29. The unit of conductance cannot be expressed in
(a) mho (b) (ohm)1
(c) siemen (d) ohm m1
30. SI unit of specific resistance is
(a) ohm m (b) ohm m1
(c) ohm m2
(d) (ohm)1
31. The slope of current (I) versus voltage (V) is called
(a) resistance (b) resistivity
(c) conductivity (d)
conductance
Y
XO V
I
32. The slope of voltage (V) versus current (I) is called
(a) resistance
(b) conductance
(c) resistivity
(d) conductivity
Y
XO
V
I

31
33. For a metallic conductor, voltage versus current graph is drawn at two different
temperatures 1T and 2T . From the graph it follows
(a) 21 TT 
(b) 21 TT 
(c) 21 TT 
(d) nothing can be decided
Y
XO
V
I
T2
T1
34. For a metallic conductor, current versus voltage graph is drawn at
two different temperatures 1T and 2T . From the graph it follows
(a) 21 TT 
(b) 21 TT 
(c) 21 TT 
(d) nothing can be decided
Y
XO V
I
T2
T1
35. What is the current (I) in the circuit
(a) A
2
1
(b) 2A
(c) A
2
3
(d) none of these
2V
I
21
1
36. The resistance of germanium will rise if temperature
(a) increases (b) decreases
(c) remains the same (d) first increases then decrease

32
37. The effective resistance of a circuit containing resistances in parallel is
(a) equal to the sum of the individual resistances
(b) smaller than any of the individual resistances
(c) greater than any of the individual resistances
(d) sometimes greater and sometimes smaller than the individual resistances
38. Electric intensity is
(a) a scalar quantity (b) a vector quantity
(c) neither scalar nor vector (d) sometimes scalar and sometimes vector
39. Electric potential is
(a) a scalar quantity (b) a vector quantity
(c) neither scalar nor vector (d) sometimes scalar and sometimes vector
40. Choose the only vector amongst the following
(a) electric potential (b) e.m.f
(c) electrical energy (d) electrostatic force
41. One ohm is equal to
(a) 6
10 mega ohm (M) (b) 9
10 M
(c) 6
10
M (d) none of these
42. In general, when the temperature of a conductor increases its resistance
(c) remains the same (d) cannot say
43. The resistance of carbon ______with rise in temperature
(c) remains the same (d) first increases then decreases
44. The resistance of a semiconductor material (germanium or silicon) _______ with rise in
temperature

33
(c) remains the same (d) first increases then decreases
45. 1 volt equals
(a) 1J (b)
J
C1
(c)
C
J1
(d) none of these
46. A graph is plotted between the potential difference (applied across the ends of a
conductor) and the current (flowing through the conductor). The graph is a straight line
(a) intersecting both the axis (b) having an intercept on the X-axis
(c) having an intercept on the Y-axis (d) none of these
47. In order to measure current in a resistance present in a circuit the ammeter is connected
(a) in series (b) in parallel
(c) in series or parallel (d) nothing can be decided
48. In our houses all electrical devices operate on 220 V. It implies that
(a) they are connected in parallel (b) they are connected in series
(c) they all have current of equal values (d) they all have the same resistance
49. What constitutes current in a metal wire?
(a) electrons (b) protons
(c) atoms (d) molecules
50. The fixed resistance is called
(a) rheostat (b) resistor
(c) key (d) switch
51. The variable resistance is called
(a) resistor (b) rheostat
(c) open switch (d) none of these
52. How much work is done in moving a charge of 2 coulombs from a point at 118 volts to a
point at 128 volts?
(a) 10J (b) 20J

34
(c) J
10
1
(d) none of these
53. The device used for measuring potential difference is known as
(a) potentiometer (b) ammeter
(c) voltmeter (d) galvanometer
54. The work done in moving a unit positive charge across two points in an electric field
circuit is a measure of
(a) current (b) resistance
(c) power (d) potential difference
55. Ohmic conductors
(a) obey ohm’s law (b) do not obey ohm’s law
(c) sometimes obey ohm’s law (d) none of these is true
56. Choose the substance which is different from others as regards conduction of electricity
(a) copper (b) aluminum
(c) silver (d) rubber
57. Which of the following has low resistivity?
(a) nichrome (b) manganin
(c) constantan (d) copper
58. Which of the following has infinitely high electrical resistance?
(a) wood (b) rubber
(c) neither (a) nor (b) (d) both (a) and (b)
59. What is the resistance across A and B in the following circuit?
(a)
4
5

(b)
5
4

(c)
3
14

(d) none of these
21
2
2
1
B
A

35
60. An electric iron draws a current 4A when connected to a 220 V mains. Its resistance must
be
(a) 1000 (b) 55
(c) 44 (d) 
4
55
61. The resistance of a conductor is reduced to half its initial value. In doing so the heating
effect in the conductor will become
(a) half (b) one-fourth
(c) double (d) four times
62. The coil of a heater is cut into two equal halves and only one of them is used in the
heater. The ratio of the heat produced by this half of the coil to that produced by the
original coils is
(a) 2 : 1 (b) 4 : 1
(c) 1 : 2 (d) 1 : 4
63. Laws of electrolysis were given by
(a) Faraday (b) Maxwell
(c) Lenz (d) Bohr
64. Laws of heating were given by
(a) Joule (b) Ohm
(c) Maxwell (d) Faraday
65. Electric iron is based upon the principle of ____ effect of current
(a) heating (b) magnetic
(c) chemical (d) none of these
66. Electric bulb converts electrical energy into
(a) sound energy (b) mechanical energy
(c) nuclear energy (d) none of these
67. The process of depositing a thin film of a metal on any conducting substance by
electrolysis is called
(a) electroplating (b) electrotyping

36
(c) polarisation (d) none of these
68. The common name of Leclanche cell is
(a) dry cell (b) Daniel cell
(c) fuel cell (d) none of these
69. The emf of a cell is measured in
(a) volt (b) watt
(c) ampere (d) kilowatt
70. Which of the following terms do not represent electrical power in a circuit:
(a) I2
R (b) IR2
(c) VI (d)
R
V2
ANSWERS TO EXERCISE – II
1. (a) 2. (b) 3. (c) 4. (b) 5. (d)
6. (b) 7. (d) 8. (a) 9. (d) 10. (d)
11. (c) 12. (c) 13. (d) 14. (a) 15. (a)
16. (b) 17. (a) 18. (d) 19. (d) 20. (a)
21. (b) 22. (d) 23. (d) 24. (a) 25. (d)
26. (a) 27. (a) 28. (c) 29. (d) 30. (a)
31. (d) 32. (a) 33. (b) 34. (c) 35. (b)
36. (b) 37. (b) 38. (b) 39. (a) 40. (d)
41. (c) 42. (a) 43. (b) 44. (b) 45. (c)
46. (d) 47. (a) 48. (a) 49. (a) 50. (b)
51. (b) 52. (b) 53. (c) 54. (d) 55. (a)
56. (d) 57. (d) 58. (d) 59. (d) 60. (d)
61. (a) 62. (c) 63. (a) 64. (a) 65. (a)
66. (d) 67. (a) 68. (a) 69. (a) 70. (b)

37
4. MAGNETIC EFFECTS OF ELECTRIC
CURRENT
Magnetic Effects of Current
(i) H.C. Oersted: He first proposed experimentally that a magnetic field is developed
around a current carrying conductor. He showed it by deflection of a magnetic needle
placed near a closed circuit, having current.
(ii) Maxwell cork-screw rule or right hand thumb rule: According to this rule
imagine yourself holding a current carrying conductor in your right hand such that thumb
points in the direction of flow of current then the fingers wrapping around it gives the
direction of flow of magnetic field.
(iii) Fleming Left hand Rule: Stretch the forefinger, the central finger and the thumb of
your left hand mutually perpendicular to each other. If the forefinger shows the direction
of the magnetic field and the central finger that of the current, then the thumb will point
towards the direction of motion of the conductor.
(iv) Fleming’s Right Hand Rule: Stretch out the forefinger, the middle finger and the
thumb of the right hand such that these are mutually perpendicular to each other. If the
forefinger shows the direction of the magnetic field, thumb shows the direction of motion
of the conductor then the middle finger gives the direction of current produced in the
conductor (Induced current).
ELECTRIC MOTOR AND ELECTROMAGNETIC INDUCTION
An electric motor is a device for converting electric energy into mechanical energy. Thus, an
electric motor is the reverse of an electric generator. There are two types of electric motors:
(i) AC motor
(ii) DC motor.
Principle of Electric motor: When a conductor or rectangular coil carrying current is placed in
between a magnet, the conductor experiences a force and moves. Thus, its converts electric
energy to mechanical energy.
Electric Generator: A device which converts mechanical energy into electrical energy is called
an electric generator.

38
Principle of Electric generator – Electromagnetic induction: When a
conductor/rectangular coil is kept in between a magnet and when there is a relative
motion between them, there is a change in magnetic flux and thus current is induced.
Thus, a generator changes mechanical energy to electrical energy.
Reasons of short-circuiting
Short-circuiting happens due to :
(a) Damage to the insulation of the power-lines
(b) A fault in an electric appliance due to which current does not pass through it.
Consequences of short-circuiting
On account of short-circuiting, resistance of the circuit decreases to a very small value
and consequently the current becomes very large. This large current results in heating of
live wires, which produces sparking at the point of short-circuiting. This sparking
sometimes causes fire in a building. (Apart from short-circuiting, the increase in current
in the circuit and consequent heating may also be due to overloading of the circuit).
Electric Fuse: A Safety Device
An electric fuse is a device, which is used in series to limit the current in an electric
circuit so that it easily melts due to overheating when excessive current passes
through it. A fuse is a wire of a material with very low melting point.
Electric fuse can avoid incidents like electric shock, fire, damage to an electric appliance
due to :
 Short-circuiting or
 Overloading (withdrawing current beyond a specified limit) in a circuit.
Earthing
Many electric appliances of daily use like electric press, toaster, refrigerator, table fan
etc. have a metallic body. If the insulation of any of these appliances melts and makes
contact with the metallic casing, the person touching it is likely to receive a severe
electric shock. This is due to the reason that the metallic casing will be at the same
potential as the applied one. Obviously, the electric current will flow through the body of
the person who touches the appliance. To avoid such serious accidents, the metal casing
of the electric appliance is earthed. Since the earth does not offer any resistance, the

39
current flows to the earth through the earth wire instead of flowing through the body of
the person. More over, due to very low resistance (almost nil) offered by the earth wire,
the current in the circuit rises to a very high value, thereby melting fuse in that circuit and
cutting off its electric supply.
Role of Magnetism in Medicine and Organisms
In our body, small electric current travels along the nerve cells due to ions. This current
produces a very weak magnetic field (about one billionth time weaker than the Earth's
magnetic field) in our body. Heart and brain are the two main organs in our body where
this magnetic field is quite significant. The magnetic field in our body enables us to
obtain the images of its different parts by using a technique called MRI (Magnetic
Resonance Imaging). On analysing the images obtained through MRI, we are able to
make a medical diagnosis, e.g., location and size of a tumour in brain etc. Thus,
magnetism plays an important role in modern medical science.
Apart from this, there are certain organisms, which have the ability to sense Earth's
magnetic field and travel from one place to another. For example, some types of fishes
are able to detect magnetic field by using special receptors whereas in certain organisms,
crystals of magnetite enable to move along the Earth's magnetic field.

40
MIND MAP
 A magnet is a substance with attractive and
directive properties.
 Magnetic field is a space around magnet
where force of attraction and repulsion is
detected.
 Magnetic field lines represent a magnetic
field.
a The lines are directed from North pole to
South pole.
b They are parallel and equidistant to each
other and form closed and continuous
curve.
 Oersted demonstrated that around every
conductor carrying an electric current there
is a magnetic field.
 The magnitude of magnetic field is (B)
 Right hand thumb rule – Imagine a straight
conductor in your right hand such that the
thumb points in the direction of current
and the curling of fingers gives the
direction of magnetic field lines.
 Fleming left hand rule – On stretching your
left hand, fore finger points in the direction
of the magnetic field, the central finger
points in the direction of current and the
thumb points in the direction of motion of
conductor.
 Fleming right hand rule – On stretching
your right hand, such that the central finger
and the first finger are mutually
perpendicular to each other, the first finger
points in the direction of magnetic field, the
thumb points in the direction of motion of
the conductor and the central finger points
in the direction of induced current.
MAGNETICEFFECTSOFELECTRICCURRENT
 The cable supplying power to house hold
has
a Live wire (red).
b Neutral wire (black)
c Earth wire (green)
 A fuse protects the electric circuits and
appliances from short circuiting or from
 Electro magnetic induction is the conversion
of mechanical energy into electrical energy.
 Electric motor is used to convert electric
energy into mechanical energy.
 Generator is used to convert mechanical
energy into electrical energy.

41
EXERCISE – I
Q. 9 – 10 are of five marks each.
1. What does a compass do?
2. What is the property of the poles?
3. What is the use of MRI?
4. Why is the earth pin of a 3-pin plug thickest?
5. Name the 2 poles of a magnet. What is AC and DC?
6. Draw a sketch of the pattern of field lines due to a current in a circular coil.
7. Differentiate between AC and DC.
8. Name the 3 wires used in a domestic circuit and mention the colour of each.
9. Draw a labelled diagram to show how electric connections are made in a house. What is
the voltage of domestic connection and that of commercial connection?
10. Answer the following:
(a) What is the right hand thumb rule? Show it diagrammatically also.
(b) Why don't 2 magnetic lines of force intersect each other?
(c) Draw magnetic field lines around a bar magnet

42
EXERCISE – II
1. Choose the correct option:
The magnetic field inside a long straight solenoid-carrying current
(a) is zero
(b) decreases as we move towards its end
(c) increases as we move towards its end
(d) is the same at all points
2. When the normal to a coil points in the direction of B, the flux is
(a) positive (b) negative
(c) zero (d) nothing cab be said
3. In a DC generator, the induced emf in the armature is
(a) DC (b) AC
(c) fluctuating DC (d) both AC and DC
4. Choose the correct option.
A rectangular coil of copper wires is rotated in a magnetic field. The direction of the
induced current changes once in each
(a) two revolutions (b) one revolution
(c) half revolution (d) one-fourth revolution
5. 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.

43
6. Ampere rule is used to find the
(a) direction of current (b) direction of magnetic field
(c) direction of motion of the conductor (d) magnitude of current
7. A compass needle just above a wire in which electrons are moving to the east, will point
(a) east (b) west
(c) north (d) south
8. By increasing the number of turns in the coil, the strength of the magnetic field
(c) first decreases then increases (d) remains uncharged
9. Fleming’s right hand rule gives
(a) the magnitude of the induced emf
(b) the magnitude of the magnetic field
(c) the direction of the induced emf
(d) both magnitude and direction of he induced emf
10. For making an electromagnet the best material for the case is
(a) stainless steel (b) soft iron
(c) silver (d) nickel
11. A wire carrying a current of 5 A is placed perpendicular to a magnetic induction of 2 T.
The force on each centimeter of the wire is
(a) 0.1 N (b) 10 N
(c) 100 N (d) 1 N
12. There will be no force between two currents if they are
(a) parallel to each other (b) antiparallel to each other
(c) perpendicular to each other (d) nothing can be said
13. A copper ring is moved towards the north pole of a bar magnet. Then
(a) the ring will not be affected (b) the ring will tend to get warm

44
(c) an alternating current will flow in the ring (d) the ring will be positively charged
14. The split rings in motion are called
(a) armature (b) commutator
(c) rotor (d) core
15. The frequency of AC mains is
(a) 100 Hertz (b) 50 Hertz
(c) 1/100 Hertz (d) 1/50 Hertz
16. A switch is always connected to the
(a) earth wire (b) neutral wire
(c) live wire (d) none of these
17. A fuse wire is always connected to the
(a) earth wire (b) neutral wire
(c) live wire (d) none of these
18. The frequency of AC used in India is
(a) 50 Hz (b) 100 Hz
(c) 200 Hz (d) none of these
19. Which of the following figures represents the magnetic lines of force due to an isolated
north pole?
(a)
N
(b)
N

45
(c)
N
(d)
N
20. Magnetic lines of force
(a) form closed circuits (b) cannot intersect
(c) are crowded together near the poles (d) all the above are coorect
21. A coil carrying current behaves as a/an
(a) magnet (b) motor
(c) dynamo (d) electric dipole
22. The wire having red plastic covering is a
(a) live wire (b) neutral wire
(c) earth wire (d) none of these
23. The wire having black plastic covering is a
24. The wire having green plastic covering is a
25. Which of the following is not associated with Fleming’s left hand rule?
(a) resistance (b) magnetic field
(c) force (d) current

46
26. If a bar magnet is cut lengthwise into 3 parts, the total number of poles will be
(a) 2 (b) 3
(c) 4 (d) 6
27. A compass needle placed just above a wire in which electrons are moving towards west,
will point
(a) East (b) North
(c) West (d) South
28. Magnetic effect of electric current was discovered by
(a) Maxwell (b) Oersted
(c) Ampere (d) none of these
29. Electric bulb converts electrical energy into
(a) sound energy (b) mechanical energy
(c) nuclear energy (d) none of these
30. Choose the wrong statement
(a) Magnetic poles always exist in pairs
(b) Magnetic poles are always of equal strength
(c) like poles repel each other
(d) unlike poles repel each other

47
1. (d) 2. (a) 3. (b) 4. (c) 5. (d)
6. (b) 7. (d) 8. (b) 9. (c) 10. (c)
11. (a) 12. (c) 13. (b) 14. (c) 15. (b)
16. (c) 17. (c) 18. (a) 19. (a) 20. (d)
21. (a) 22. (a) 23. (b) 24. (c) 25. (a)
26. (d) 27. (b) 28. (b) 29. (d) 30. (d)

48
5. SOURCES OF ENERGY
IMPORTANT FACTS:
• A source of energy provides energy in a convenient form over a long period of time.
• Sources of energy can be classified as renewable and non-renewable sources.
• Solar energy is the main source of energy on the earth.
• Solar cookers, solar water heaters and solar concentrators are some devices used for
harnessing solar energy.
• Solar cells are devices that convert solar energy directly into electricity.
• Solar energy also manifests itself in nature as the energy of winds, water flowing through
rivers, ocean waves, besides ocean thermal energy.
• Energy harnessed through wind energy devices is utilized either to do mechanical work,
or to produce electricity.
• Energy derived from the hot spots beneath the earth is called geothermal energy.
• Green plants convert solar energy into chemical energy through the process of
photosynthesis. This energy is known as bio-energy.
• Biomass is utilized to produce heat by burning it or to produce biogas through its
anaerobic decomposition in a biogas plant.
• Hydrogen and alcohol could be a source of energy in future.
• Fossil fuels like coal, petroleum and natural gas are a mixture of hydrocarbons. These are
fossil remains produced by the decay of plants and marine animals that were buried in the
earth millions of years ago.
• Fuels like coal, petroleum and natural gas are being utilized at very high rates, resulting
in fast depletion of their known reserves. Fossil fuels may not be available in future, as
these are not being formed now.
• Fuels are characterized by their calorific value and ignition temperature, besides the
nature of product produced by their combustion.
• The three conditions essential for combustion are attainment of ignition temperature,
presence of oxygen and a combustible material.

49
• The factors that help to choose a good fuel for a given purpose are its availability, cost,
its characteristic and physical properties, besides considerations of the effects of its by-
products on environment.
TYPES OF ENERGY
1. Wind Energy: The energy possessed due to moving air is called wind energy.
Advantages:
(i) It does not cause any pollution.
(ii) The source of wind energy is air. (Renewable Energy)
(iii) It is available free of cost.
2. Water Energy: The energy possessed due to flowing of water is called the water energy.
Water Wheel: The device used for obtaining energy from flowing water is called
water wheel. The basic principle of water wheel is that the moving water rotates the water
wheel and this water wheel can be made to turn machines, which do work for us.
3. Electric Power Plants: The set-up, which can produce large quantity of electricity,
from a few kilowatts to a few hundred megawatts, are called power plants. There are
three types of power stations (plants). These are:
(a) Hydroelectric power stations;
(b) Thermal power stations;
(c) Nuclear (or atomic power stations)
Principle of hydroelectric power: The potential energy of the water stored at great
heights in the dams is converted into kinetic energy by flowing water to flow at high
speeds due to which electricity is generated. The electric power so generated is called
hydroelectric power.
4. Solar Energy: The energy obtained from the sun is called solar energy.
Advantages of Solar Energy
(i) It is inexhaustible source of energy.
(ii) It does not cause pollution.
(iii) It is available free of cost.

50
Disadvantages of Solar Energy:
(i) It is not available all the time.
(ii) It is very much diffused and scattered.
5. Tidal Energy: The energy obtained from tides is called tidal Energy.
Merits of tidal energy
 It is an inexhaustible source of energy.
 It is independent of uncertainty of rainfall.
 It is a pollution free source of energy.
 It does not require large area of valuable land.
Demerits of tidal energy
 Power generation is intermittent due to variation in tidal range.
 The most difficult problem in the use of tidal power are the barrage construction in
areas of high tidal flow and corrosion of barrage.
6. Merits of wave energy
 It is a renewable and pollution free source of energy.
 It does not require large land areas.
Demerits of wave energy
 The power supply is variable in nature due to variability in wave formation.
 It is expensive.
 Marine life could be affected due to wave energy harnessing structures.
7. Merits of OTEC
 The electric power produced is continuous, renewable and pollution free.
 OTEC system enriches the fishing grounds by transferring nutrients from the
unproductive deep waters to the warmer surface.
 OTEC system does not have daily or seasonal variations in their output as in case
with the solar energy devices.

51
Demerits of OTEC
 OTEC system requires a lot of capital investment.
 The conversion efficiency is low as there is small temperature difference between the
surface water and the deep water.
8. Merits of geothermal energy
 It is the most versatile and least polluting renewable source of energy.
 It is relatively inexpensive and power generation level is higher as compared to solar
energy and wind energy.
Demerits of geothermal energy
 Though geothermal energy is inexhaustible, a single bore has a limited life span of
about 10 years.
 Geothermal hot spots are scattered.
 Noise pollution is caused by drilling operations at geothermal sites.
9. Advantages of nuclear fusion over nuclear fission
Energy released in fusion reaction is much greater than energy released in fission
reaction. The products of fusion are not radioactive whereas it is radioactive in case of
nuclear fission and require careful disposal.
Hazards of nuclear power generation and safety measures
The major hazards of nuclear power generation are:
 Storage and disposal of spent or used nuclear fuels as they continue to decay into
harmful subatomic particles (radiations). This would lead to environmental
contamination.
 There is a risk of accidental leakage of nuclear radiation.
 It has high cost of installation of a nuclear power plant.
Types of Nuclear Reactions:
(i) Nuclear Fusion Reaction: The process in which two or more nuclei of lighter
atoms combine to form a heavy nucleus with the liberation of a large amount of energy is
called fusion reaction. For example:

52
MeV)(17.3Energy.TremendousHeHH 4
2
2
1
2
1 
(ii) Nuclear Fission Reactions: The process of splitting of a nucleus of a heavy atom
into a number of nuclei of smaller mass with the liberation of large amount of energy is
called nuclear fission. For example
MeV)(200Energyn3KrBanU 1
0
94
36
139
56
1
0
235
92 
Cause of tremendous Amount of Energy: The cause of tremendous amount of energy during
the nuclear fission is the loss of mass. The loss of mass is also called mass defect.
Einstein Equation: 2
mcE 
Where m = The mass lost or mass defect. c = the velocity of light. E = amount of energy.
Chain Reaction: A reaction in which the number of neutrons goes on increasing during fission
till whole of the fissionable material is disintegrated.
Nuclear Reactor: It is a device, which is used for carrying out fission reaction at a controlled
rate. It is used to generate electricity.
Nuclear fuel: The fissionable material used in the nuclear reactor is called nuclear fuel.
For ex., U235
, Pu239
.

53
MIND MAP
Conventional sources of energy
(a) Fossil fuels : They meet maximum of our
energy demands.
 Coal : It is the abundant fossil fuel on Earth and
is the principle source of heat for electricity
generation.
 Petroleum : A number of useful components
like kerosene, diesel, petrol, petroleum gas are
obtained from petroleum by fractional
distillation.
(b) Thermal power plant : It generates electric
power from heat produced by burning fossil
fuels i.e. , coal and petroleum.
(c) Hydro energy : The kinetic energy of flowing
water is used to generate hydroelectricity.
(d) Bioenergy : Biomass (plant and animal
products) is the source of bioenergy.
 Biogas is obtained by the anaerobic
degradation of biomass.
 It is composed of me thane (serves as a fuel),
CO2, nitrogen and phosphorus (serves as
manures).
(e) Wind energy : The kinetic energy possessed by
air due to its velocity is called wind energy.
 A wind mill converts the wind energy into
mechanical or electrical energy.
Non-conventional sources of energy
(a) Solar energy : The Earth receives only
0.1% of the enormous amount of energy
radiated by sun.
 Solar energy devices are used to harness
the heat of solar energy.
(i) Solar cookers work on the principle of
green house effect and is used for
cooking purposes.
(ii) Solar cells and solar panels convert solar
energy directly into electricity.
(b) Energy from oceans : The oceans are
huge reservoirs of energy. Tidal energy
wave energy and ocean thermal energy
are the various forms of energy
harnessed from oceans.
(c) Geothermal energy : Thermal energy
within rock formations and fluids held
within those formations.
(d) Nuclear energy : The energy obtainable
from the nucleus of an atom is called
nuclear energy or atomic energy.
SOURCESOFENERGY

54
EXERCISE – I
Q. 14 – 20 are of three marks each.
Q. 21 and 22 are of five marks each.
1. What is a wind energy farm?
2. Name some sources of energy?
3. What in our biggest source of energy?
4. Name two appliances that use solar energy directly.
5. Name two types of energy which do not relate to the sun.
6. Name one practical application of nuclear fission.
7. What is the source of energy in nuclear fission and fusion?
8. What is the drawback of energy obtained from fusion?
9. Write the advantages of nuclear fusion over nuclear fission.
10. What is the cause of ocean thermal energy?
11. What is a solar cell? Name two materials mostly used for making solar cells.
12. How were fossil fuels formed?
13 .What is nuclear fusion? Give an example for it.
14. The use of dry wood as domestic fuel is not considered as good. State two reasons for it.
15. Describe a concentrator type solar cooker.
16. What is tidal energy? How it is harnessed ?
17. Compare and contrast fossil fuels and sun as sources of energy.
18. What are the qualities of an ideal source of energy?

55
19. What are the advantages and disadvantages of using a solar cooker? Are there places
where solar cookers would have limited utility?
20. Write the merits and demerits of geo-thermal energy.
21. Give the principle, construction and operation of a box-type solar cooker.
22. What is OTEC? How does on OTEC power plant works? Write the merits and demerits
of OTEC.
EXERCISE – II
1. Which one of the following does not relate to the solar energy?
(a) Wind energy (b) Tidal energy
(c) Nuclear energy (d) Wave energy.
2. The major cause of environmental pollution is the use of :
(a) Ocean energy (b) Hydrogen as a fuel
(c) Biomass energy (d) Fossil fuels.
3. The coal reservoirs in our country are expected to last for another :
(a) 400 years (b) 500 years
(c) 1000 years (d) 200 years.
4. A tree usually matures in more than :
(a) 50 years (b) 60 years
(c) 15 years (d) 100 years
5. The energy received by the Earth directly from the Sun is approximately which
percentage of the Sun’s total energy output?
(a) 1% (b) 0.001%

56
(c) 0.00000006% (d) 0.00005%
6. The approximate value of solar constant is :
(a) 1.4 kJ/min (b) 1.4 kWh/min
(c) 1.4 kW/m2
(d) 1.4 kW/min.
7. The percentage of the solar energy reaching the Earth received by the plants is :
(a) 5% (b) 1%
(c) 10% (d) 0.1%
8. An example of renewable source of energy is :
(a) Coal (b) Petroleum
(c) Sun (d) Natural gas
9. What percentage of solar energy that strikes the periphery of the Earth is trapped by
Earth?
(a) 75% (b) 47%
(c) 15% (d) 100%
10. The fraction of sunlight which consists of infrared radiation is :
(a)
2
1
(b)
3
1
(c)
4
1
(d)
3
2
11. The heat in the sunlight is due to :
(a) ultra-violet radiation (b) infra-red radiation
(c) visible radiation (d) entire solar radiation
12. Efficiency of modern solar cells is :
(a) 100% (b) 90%
(c) 60% (d) 25%

57
13. The production of solar cookers on a commercial scale in India began in :
(a) 1950 (b) 1970
(c) 1962 (d) 1980
14. A good fuel is one which possesses :
(a) high ignition temperature (b) high calorific value
(c) moderate ignition temperature (d) both (b) and (c)
15. Which of the following variety of coal contains the highest percentage of carbon?
(a) Lignite (b) Bituminous
(c) Anthracite (d) Peat
16. The main constituent of natural gas is :
(a) butane (b) methane
(c) hydrogen (d) oxygen
17. LPG consists mainly of :
(a) methane (b) ethane
(c) butane (d) liquid hydrogen
18. The fraction of the total solar energy received by the earth is :
(a) one hundred (b) one thousand
(c) one billionth (d) one millionth
19. The approximate temperature of the surface of the Sun is :
(a) 3000C (b) 30000C
(c) 6000C (d) 10000C
20. Which of the following is a primary fuel ?
(a) Kerosene (b) Wood
(c) Petrol (d) Diesel

58
21. Which of the following is a secondary fuel?
(a) Wood (b) Coal
(c) Diesel (d) Natural gas
22. The device which harnesses solar energy directly is :
(a) Coal gas plant (b) Natural gas plant
(c) Solar cell (d) Biogas plant
23. U-235 content in natural uranium is :
(a) 0.006% (b) 0.714%
(c) 99.2% (d) 100%
24. Energy released in the fission of one nucleus of U-235 is about :
(a) 1 Me V (b) 20 Me V
(c) 200 Me V (d) 2000 Me V
25. Energy released in the fission of 1 kg of U-235 is equivalent to energy obtained from
burning of coal weighing :
(a) 25 ton (b) 250 ton
(c) 25000 ton (d) 25000 ton
26. One Me V of energy is equivalent to :
(a) 1.6  1013
J (b) 1.6  1019
J
(c) 1.6  1013
J (d) 1.6  1019
J
27. One unified atomic mass unit (u) is equivalent to :
(a) 1 eV (b) 1 Me V
(c) 931 Ne V (d) 931 eV
28. Common moderator used in nuclear reactor is :
(a) graphite (b) cadmium
(c) boron (d) uranium

59
29. Disposal of nuclear waste is a challenge because
(a) too large (b) too heavy
(c) radioactive (d) foul smelling
30. Uncontrolled nuclear chain reaction is the basis of :
(a) nuclear reactor (b) atoms bomb
(c) hydrogen bomb (d) none of these
1. (c) 2. (d) 3. (d) 4. (c) 5. (c)
6. (c) 7. (b) 8. (c) 9. (b) 10. (a)
11. (b) 12. (d) 13. (c) 14. (d) 15. (c)
16. (b) 17. (c) 18. (c) 19. (c) 20. (b)
21. (c) 22. (c) 23. (b) 24. (c) 25. (c)
26. (a) 27. (c) 28. (a) 29. (c) 30. (b)

60
6. CHEMICAL REACTIONS AND EQUATIONS
DIFFERENCE BETWEEN PHYSICAL CHANGE AND CHEMICAL CHANGE
Physical Change Chemical Change
(i) Those changes in which no new
substances are formed are called
physical changes
(i) Those changes in which the original
substances lose their chemical nature and
identity and form new chemical substances
with different properties are called
chemical changes
(ii) It is a temporary change (ii) It is a permanent change
(iii) It is easily reversible (iii)It is usually irreversible
(iv) In a physical change the mass of
substance does not alter
(iv) In a chemical change the mass of the
substance does alter
CHEMICAL REACTION: The process by which two or more chemical substances
interact to form some new substances with different chemical properties. Chemical
reactions are represented by balanced chemical equations with the help of chemical
symbols of the substances involved.
Characteristics of chemical reactions: The easily observable changes that take place in
a chemical reaction are called characteristics of chemical reaction.
 Formation of Precipitate: Example
AgNO3 (aq) + NaCl(aq)  AgCl (ppt) + NaNO3 (aq)
 Evolution of gas : Example
Zn(s) +
dil
HCl ZnCl2 + 2H
 Change in Colour: Example
Pb(NO3)2(aq) + KI(aq)    (aq)KNOpptPbI 32 
Yellow
 Change in state: Example
Solid wax burns to form water vapour and carbon dioxide.
 Change in temperature: Example

61
CaO + H2O  Ca(OH)2 + Heat (Exothermic)
  OH
4
NH
2
BaClHeatCl
4
NH2OHBa  (Endothermic)
Types of Chemical Reactions
Combination
reactions
Decomposition
reactions
Displacement
reactions
Double displacement
reactions
Oxidation – Reduction
(Redox) Reactions
Types of Chemical Reactions:
(i) Addition or combination reaction: Two or more substances combine to form a
single substance.
CaO + CO2  CaCO3
(ii) Decomposition reaction: One chemical substance splits to give two or more
substances either by heat energy (Thermolysis) or light (Photolysis) or by electricity
(Electrolysis).
Thermolysis
3223 NONOPbO)NO(Pb 

Electrolysis

  OHHOH
current
electric
2
Photolysis
2AgCl  2Ag + Cl2
(iii) Displacement Reaction: More reactive element displaces less reactive element
from its compound or salt.
Fe + CuSO4  FeSO4 + Cu
(iv) Double Displacement Reaction: Two elements interchange their respective salts or
ions to form new compounds.
FeCl3 + CuSO4  FeSO4 + CuCl2

62
(v)
(a) Oxidation (b) Reduction
 addition of oxygen or
 removal of hydrogen or
 loss of electrons
Natural oxidation in everyday life:
 Corrosion & Rancidity
 loss or removal of oxygen
 gain or addition of hydrogen
 gain of electrons
Natural reduction in everyday life:
 Hydrogenation
Redox Reactions : Both oxidation and reduction taking place simultaneously in the same
chemical reaction.
Oxidizing agent : A substance which brings about the oxidation of other substance but
itself gets reduced in a reaction.
Reducing agent : A substance which brings about reduction of the other substance but
itself gets oxidized in a reaction
Some examples of redox reactions :
(a)
Zn + Cu2+
Zn2+
+ Cu
Oxiding Gain of electrons : Reduction
agent
Loss of electrons : oxidation
Zn + CuSO4 ZnSO4 + Cu
Reducing
agent
(b)
Cu + 2Ag+
Cu2+
+ 2Ag
Reducing
Loss of electrons : Oxidationagent
oxidising
agent
Gain of electrons : Reduction
Cu + 2AgNO3 Cu(NO3)2 + 2Ag
(c)
Mn4+
+ 2Cl–
Mn2+
+ Cl2
oxidising
Gain of electrons : Reduction
agent
Reducing
agent
Loss of electrons : oxidation
MnO2 + 4HCl MnCl2 + Cl2 + 2H2O

63
MIND MAP
The symbolic representation of a true
chemical change or reaction is called a
chemical equation.
CHEMICAL REACTION
AND EQUATION
 In a chemical equation reactants,
products and their physical state are
represented symbolically
 Physical States of reactants and
products are represented by notations
s, l, g and aq.
 The chemical equations are balanced to
satisfy the law of conservation of mass.
 Law of conservation of mass : “Matter
can neither be created nor destroyed.
Reactions are made more informative
by indicating the
 Physical state of reactants and
products
 Heat changes
 Conditions under which the reaction
takes place.
Types of Chemical reaction
 Combination reaction
 Decomposition reaction
 Displacement reaction
 Double displacement reaction
 Redox reaction.
Combination reaction
Reaction in which two or more
substances combine together to form a
single substance.
Decomposition reaction
In this reaction a single substance
breaks into two or more simpler
substances. It is of three types :
 Thermal decomposition
 Electrolytic decomposition
 Photolytic decomposition
Displacement reaction
In this reaction a more reactive element
displaces a less reactive element from its
compound.
Double displacement reaction
In this reaction two different atoms or
group of atoms are exchanged.
Redoxreaction
In this reaction oxidation and reduction take
place simultaneously.
Corrosion of metals
The slow process of eating up of
metals due to attack of atmospheric
gases.
Rancidity
Oxidation of oils or fats in a food
resulting into a bad smell and bad
taste.

64
EXERCISE – I
1. In the refining of silver, the recovery of silver from silver nitrate solution involved
displacement by copper metal. Write down the reaction involved.
2. Why are bags of fat and oil containing food items (like chips) flushed with nitrogen?
3. When is a substance said to be reduced?
4. What type of reactions are represented by the following equation?
(a) NH4Cl  NH3 + HCl
(b) 2H2 + O2  2H2O
(c) BaCl2 + Na2SO4  BaSO4 + 2NaCl
(d) Mg + CuSO4  MgSO4 + Cu
5. Can silver nitrate (AgNO3) solution be stored in an iron container? Explain your answer.
6. What is meant by a decomposition reaction? Explain with the help of an example.
7. What happens when silver chloride is exposed to sunlight? Write a chemical equation for
this reaction. Name the type of reaction which takes place. Also give one use of such a
reaction.
8. Write one equation each for decomposition reactions where energy is supplied in the
form of (a) heat (b) light, and (c) electricity.
9. Why does the colour of copper sulphate solution fade when an iron nail is dipped in it?
Explain with the help of an equation.
10. What happens when a strip of zinc is placed in copper sulphate solution? Write equation
of the reaction involved. Name the type of chemical reaction which takes place.
11. What is meant by a double displacement reaction? Explain with the help of an example.
12. What do you mean by a precipitation reaction? Explain by giving example.
13. When a green iron salt is heated strongly, its colour finally changes to brown and odour
of burning sulphur is given out:
(a) Name the iron salt and write its formula.

65
(b) Name the brown substance obtained and write its formula.
(c) Which product gives the odour of burning sulphur? Write its formula.
(d) Write the chemical equation of the reaction involved.
(e) Name the type of chemical reaction which takes place during the heating of iron salt.
14. Explain the term ‘rancidity’ with an example. How can rancidity be prevented of
retarded?
15. (a) What are redox reactions? Explain giving two examples.
(b) Can oxidation or reduction take place alone? Justify your answer.
EXERCISE – II
1. Balance the following chemical equations:
(i) Fe + H2O  Fe3O4 + H2 (ii) Na + H2O  NaOH + H2
2. Give two examples of reduction reaction?
3. Why do we apply paint on iron articles?
4. What do you mean by precipitation reaction? Give its example.
5. Write a balanced chemical equation with state symbols for the following reactions:
(i) Solutions of barium chloride and sodium sulphate in water react to give insoluble
barium sulphate.
(ii) Sodium hydroxide solution (in water) reacts with hydrochloric acid solution (in
water) to produce sodium chloride solution and water.
6. What are redox reaction? Give its two examples:
7. Translate the following statements into chemical equations and then balance them:
(i) Hydrogen gas combines with nitrogen gas to form ammonia.
(ii) Hydrogen sulphide gas burns in air to give water and sulphur dioxide.
(iii)Potassium metal reacts with water to give potassium hydroxide and hydrogen gas.
(iv)Barium chloride reacts with aluminium sulphate to give aluminium chloride and
precipitate of barium sulphate.
8. Balance the following chemical equations:
(i) HNO3 + Ca(OH)2  Ca(NO3)2 + H2O(ii) NaOH + H2SO4  Na2SO4 + H2O
(iii)BaCl2 + H2SO4  BaSO4 + HCl

66
9. Write the balanced chemical equation of the following and identify the type of reaction in
each case:
(i) Potassium bromide (aq) + Barium iodide aq)  Potassium iodide(aq) + Barium
bromide(s)
(ii) Zinc carbonate (s)  Zinc oxide (s) + Carbond dioxide (g)
(iii)Magnesium (s) + Hydrochloric acid (aq)  Magnesium chloride (aq) +
Hydrogen(g)
10. What do you mean by exothermic and endothermic reaction? Give examples:
11. Why is respiration considered as an exothermic reaction? Explain.
12. Why are decomposition reactions called the opposite of combination reactions? Write
equations for these reactions.
13. Write the balanced equation for the following chemical reactions:
(i) Hydrogen + Chlorine  Hydrogen Chlorine
(ii) Barium chloride + Aluminium sulphate  Barium sulphate + Aluminium
chloride
(iii)Sodium + Water  Sodium hydroxide + Hydrogen
14. A solution of a substance X is used for white-washing:
(i) Name the substance X and write its formula
(ii) Write the reaction of the substance X named in (i) above with water.
15. Why does the colour of copper sulphate solution change when an iron nail is dipped in it?
EXERCISE – III
1. Write an activity to show the change in the state of matter and change in temperature
during a chemical reaction
2. Write one activity to show the decomposition of a chemical compound with the evolution
of a gas.
3. Write an activity to show the electrolysis of water, as an example of decomposition
reaction.
4. Name different types of chemical reactions. Define them and give their examples.
5. What is a balanced chemical equation? Why should chemical equations be balanced?
6. To balance a chemical equation, can we change the formulae of either reactants of
products?

67
7. Write an equation for decomposition reactions where energy is supplied in the form of
heat, light or electricity.
8. What is the difference between displacement and double displacement reaction? Write
equations for these reactions.
9. How do we come to know, that a chemical reaction has taken place?
10. Explain the following in terms of gain or loss of oxygen with two examples each:
(a) Oxidation (b) Reduction
11. A shiny brown coloured element X on heating in air becomes black in colour. Name the
element X and the black coloured compound formed.
12. Why do we apply paint on iron articles?
13. Oil and fat containing food items are flushed with nitrogen. Why
14. Explain the following terms with one example each:
(a) Corrosion (b) Rancidity
15. Identify the substance that the oxidized and the substances that are reduced in the
following reactions:
(i) 4Na(s) + O2(g)  2Na2O (s)
(ii) CuO(s) + H2(g)  Cu(s) + H2O (l)

68
7. ACIDS, BASES AND SALTS
Indicators
Synthetic
Methyl orange Phenolphthalein
Natural
Dyes (Indicators
of colour)
Olfactory
Indicators of
smell
Onion extract Clove oilVanilla essence
Red litmus Blue litmus
Indicator Colour in acidic solution Colour in basic solution
Blue litmus solution
Red litmus solution
Phenolphthalein
Methyl orange
Red
No colour change
Colourless
Pink
No colour change
Blue
Pink
Yellow
Physical properties of Acids and Bases:
Acids Bases
 Sour taste
 Turns blue litmus to red
 Provides H+
ions
when dissociated
 pH less than 7
 strong acids
HCl, HNO3,
H2SO4
 weak acids
H2CO3
CH3COOH
H3PO4
 Bitter taste
 Turns red litmus to blue
 Provides OH–
ions
when dissociated
 Bases dissolve in
water to give alkalies
 pH more than 7 upto 14
 strong base
NaOH, KOH
 weak base
NH4OH

69
Chemical properties of Acids and Bases:
Type of Reaction Acid Base
1. Neutralization
reaction
Acid + Base  Salt + H2O
Example:
HCl + NaOH  NaCl + H2O
Acid + Base  Salt + water
Example:
CaO + HCl(aq)  CaCl2(aq) + H2O (l)
2. Reaction with
metals
Acid + Metal  Metallic salt + H2(g)
Example:
Zn(s) + dil H2SO4 (aq)  ZnSO4 (aq) + H2(g)
Base + Metals  Salt + H2(g)
Example:
NaOH + Zn  Na2ZnO2 + H2
Only active metals like Zn and Al reacts
with bases.
3. Reaction with
carbonates
Acid + Carbonates  Metallic salt + CO2(g)
+ H2O
Example:
Na2CO3+ H2SO4  Na2SO4 + H2O + CO2
Base + carbonate  No reaction
4. Reaction with
bicarbonates
Acid + Bicarbonates  Metallic salt +
CO2(g) + H2O
Example:
NaHCO3+ HCl  NaCl + H2O + CO2
Base + bicarbonate  No reaction
5. Reaction with
oxide
Acid + Metal Oxide  Salt + H2O
Example:
CaO + HCl (aq)  CaCl2 (aq) + H2O
Base + Non-metallic oxide  Salt + water
Example:
Ca(OH)2 + CO2 CaCO3 + H2O
6. Dissolution in
water
Acid gives H+
ions in water.
Examples: HCl (aq)  H+
+ Cl–
H2SO4 (aq)  2H+
+ 2
4SO
Bases gives OH–
ions in water.
Examples: NaOH (aq)  Na+
+ OH–
Ca(OH)2 (aq)  Ca2+
+ 2(OH)–
Strength of acids & bases
 Strong Acids and strong bases when dissolved in water dissociate completely into
(H+
) and (OH–
) ions respectively.
 Weak acids and weak bases when dissolved in water dissociate partially into (H+
)
and (OH–
) ions respectively. Rather then remain in molecular form.

70
pH SCALE
pH scale: A scale of numbers from 0 to 14 on which
the strength of an acid or base is measured is known as pH
scale.
pH is defined as negative logarithm of ]OH[or]H[ 3

i.e. ]OHlog[pHor]H[logpH 3


0 7 14
Acidic
Neutral
Basic
Increasing
H+
ions
Decreasing
H+
ions
H2O
CO
N2O
Importance of pH in everyday life:
(i) In digestive system  (i) acidic in stomach (ii) basic (alkaline) in duodenum
(ii) Tooth decay
(iii) Nature of soil
(iv) Plants and Animals are pH sensitive
(v) Self defense by animals and plants through chemical warfare
SALTS : They are the neutralization products of acids and bases.
Classification of Salts : Salts can be classified after ‘salt hydrolysis’.
Type of salts Hydrolysis of salts
1. pH = 7 Salts of strong acid and strong bases
Example: 4242 SOK,SONaKCl,NaCl,
)aq(Cl)aq(Na)aq(NaClOH)s(NaCl 2


2. pH < 7 Salts of strong acids and weak bases
Example: 44 CuSO,ClNH
)aq(Cl)aq(NH)aq(ClNHOH)s(ClNH 4424


OHNH 24 
 
 HOHNH4
The solution is acidic due to the 
H ion produced by the hydrolysis of

4NH
3. pH > 7 Salt of weak acid and strong base
Example: COONaCH,CONa 332
)aq(Na)aq(COOCH)aq(COONaCHOH)s(COONaCH 3323



 OHCOOHCH3OHCOOCH 23 

71
The solution is basic due to hydrolysis of )aq(COOCH3

4. pH  7 Salt of weak acid & weak base
Example: 43COONHCH

 4343243 NHCOOCH)aq(COONHCHOHCOONHCH

 OHCOOHCH3OHCOOCH 23 
OHNH 24 
 
 HOHNH4
Common Salt  NaCl  Chemicals obtained from NaCl
(i) NaOH (by chlor-alkali process)
22Current
Electric
2 HClNaOHOHNaCl  
(ii) Bleaching power (CaOCl2)
2222 HCaOClCl)OH(Ca 
(iii) Baking soda (NaHCO3)
323
Brine
2 NaHCOCONHOHNaCl 

(iv) Washing soda (Na2CO3 · 10H2O)
OHCONaNaHCO 2323 

Other Important Salts:
Plaster of Paris (POP)  CaSO4 · OH
2
1
2
POP
24
k273
Heat
Gypsum
24 OH
2
1
·CaSOOH2·CaSO  

72
MIND MAP
Indicator: Substance which shows one
characteristic property in one medium
and different property in another
medium are called indicators.
 Natural indicator: Litmus solution,
turmeric
 Synthetic indicator:
Phenolphthalein, methyl orange
 Olfactory indicator: Onion, clove
oil, vanilla extract.
Acid: Substances which give H+
ion in
solution.
 Strong acid: dissociate completely,
e.g. HNO3, HCl, H2SO4.
 Weak acid: do not dissociate
completely, e.g. CH3COOH, H2CO3.
 Concentrated acid: gives more H+
ion.
 Dilute acid: gives less H+
ion.
 Acid
Metal
Metal carbonate
Base
Metal oxide
Salt + H2
Salt +CO2 + H2O
Salt + H2O
Salt + H2O
 The properties of an acid is due to
[H+
] ion, which it gives in aqueous
solution.
ACIDS,BASESAND
SALTS
Base: Substances which give OH–
ion in
solution.
 Strong base: dissociate completely,
e.g. NaOH, KOH.
 Weak base: do not dissociate
completely, e.g. NH4OH.
 Base
Metal
Acid
Non-metal
Salt + H2
Salt + H2O
Salt + H2Ooxide
 The properties of a base are due to
[OH–
] ion, which it gives in aqueous
solution.
 Strength of an acid or base  Degree of ionization
 Strength of an acid or base 
baseoracidanofdilution
1
 The properties of an acid or base is due to [H+
] ion, [OH–
]
ion, respectively which they give in aqueous solution.
 Dilution of an acid or base is an exothermic reaction.
pH scale: A scale of numbers from 0 to
14 on which the strength of an acid or
base is measured
pH = –log[H+
] or pH = –log[H3O+
]
 For a neutral solution
[H+
]= [OH–
] = 10–7
mol/L; pH = 7
 For an acidic solution
[H+
] > [OH–
]; pH < 7
 For a basic solution
[H+
] < [OH–
]; pH > 7
Salt: The ionic compound consisting of
two parts, one containing a positive
charge (cation) and the other carrying a
negative charge (anion)
 Salt of strong acid and strong base:
NaCl, KCl
 Salt of strong acid and weak base:
NH4Cl.
 Salt of weak acid and strong base:
CH3COONa.
 Salt of weak acid and weak base:
CH3COONH4.
Some chemical compounds
 Sodium hydroxide (NaOH)
 Bleaching powder or Calcium
Oxychloride(CaOCl2)
 Washing Soda or Sodium Carbonate
(Na2CO3)
 Baking Soda or Sodium bicarbonate
(NaHCO3)
 Plaster of Paris (CaSO4½H2O)
 Gypsum (CaSO42H2O)

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