NCERT Textbook: Electricity & Circuits

# NCERT Textbook: Electricity & Circuits | Science & Technology for UPSC CSE PDF Download

``` Page 1

95 ELECTRICITY AND CIRCUITS
9
Electricity and Circuits
W
e use electricity for many
easier. For example, we use
electricity to operate pumps that lift
water from wells or from ground level
to the roof top tank. What are other
purposes for which you use electricity?
List some of them in your notebook.
Does your list include the use of
electricity for lighting? Electricity
makes it possible to light our homes,
even after sunset. This helps us to
continue working at night. A power station
provides us with electricity. However, the
supply of electricity may fail or it may not
be available at some places. In such
situations, a torch is sometimes used for
providing light. A torch has a bulb that
lights up when it is switched on. Where
does the torch get electricity from?
9.1. ELECTRIC CELL
Electricity to the bulb in a torch is
provided by the electric cell. Electric cells
are also used in alarm clocks,
and many other devices. Have you ever
carefully looked at an electric cell?  You
might have noticed that it has a small
metal cap on one side and a metal disc
on the other side (Fig. 9.1). Did you
notice a positive (+) sign and a negative
(–) sign marked on the electric cell? The
Fig.9.1 An Electric Cell
metal cap is the positive terminal of the
electric cell. The metal disc is the
negative terminal. All electric cells have
two terminals; a positive terminal and a
negative terminal.
An electric cell produces electricity
from the chemicals stored inside it.
When the chemicals in the electric cell
are used up, the electric cell stops
You might have seen the  danger sign shown here displayed on poles,
electric substations and many other places. It is to warn people that
electricity can be dangerous if not handled properly.  Carelessness in
handling electricity and electric devices can cause severe injuries and
sometimes even death. Hence, you should never attempt to experiment
with the electric wires and sockets. Also remember that the electricity
generated by portable generators is equally dangerous. Use only electric
cells for all activities related to electricity.
Caution
Rationalised 2023-24
Page 2

95 ELECTRICITY AND CIRCUITS
9
Electricity and Circuits
W
e use electricity for many
easier. For example, we use
electricity to operate pumps that lift
water from wells or from ground level
to the roof top tank. What are other
purposes for which you use electricity?
List some of them in your notebook.
Does your list include the use of
electricity for lighting? Electricity
makes it possible to light our homes,
even after sunset. This helps us to
continue working at night. A power station
provides us with electricity. However, the
supply of electricity may fail or it may not
be available at some places. In such
situations, a torch is sometimes used for
providing light. A torch has a bulb that
lights up when it is switched on. Where
does the torch get electricity from?
9.1. ELECTRIC CELL
Electricity to the bulb in a torch is
provided by the electric cell. Electric cells
are also used in alarm clocks,
and many other devices. Have you ever
carefully looked at an electric cell?  You
might have noticed that it has a small
metal cap on one side and a metal disc
on the other side (Fig. 9.1). Did you
notice a positive (+) sign and a negative
(–) sign marked on the electric cell? The
Fig.9.1 An Electric Cell
metal cap is the positive terminal of the
electric cell. The metal disc is the
negative terminal. All electric cells have
two terminals; a positive terminal and a
negative terminal.
An electric cell produces electricity
from the chemicals stored inside it.
When the chemicals in the electric cell
are used up, the electric cell stops
You might have seen the  danger sign shown here displayed on poles,
electric substations and many other places. It is to warn people that
electricity can be dangerous if not handled properly.  Carelessness in
handling electricity and electric devices can cause severe injuries and
sometimes even death. Hence, you should never attempt to experiment
with the electric wires and sockets. Also remember that the electricity
generated by portable generators is equally dangerous. Use only electric
cells for all activities related to electricity.
Caution
Rationalised 2023-24
96 SCIENCE
producing electricity. The electric cell
then has to be replaced with a new one.
A torch bulb has an outer case of
glass that is fixed on a metallic base
[Fig. 9.2 (a)]. What is inside the glass
case of the bulb?
Activity 1
Take a torch and look inside its bulb.
You can also take out the bulb with the
help of your teacher. What do you
notice? Do you find a thin wire fixed in
the middle of the glass bulb [Fig. 9.2
(b)]? Now switch the torch on and
observe which part of the bulb is
glowing.
The thin wire that gives off light is
called the filament of the bulb. The
filament is fixed to two thicker wires,
which also provide support to it, as
shown in Fig. 9.2 (b). One of these thick
wires is connected to the metal case at
the base of the bulb [Fig. 9.2 (b)].  The
other thick wire is connected to the
metal tip at the centre of the base. The
base of the bulb and the metal tip of the
base are the two terminals of the bulb.
These two terminals are fixed in such a
way that they do not touch each other.
The electric bulbs used at home also
have a similar design.
Thus, both the electric cell and the
bulb have two terminals each. Why do
they have these two terminals?
9.2 A BULB CONNECTED TO
AN ELECTRIC CELL
Let us try to make an electric bulb light
up using an electric cell.  How do we do
that?
Activity 2
Take four lengths of electric wire with
differently coloured plastic coverings.
Remove a little of the plastic covering
from each length of wire at the ends.
This would expose the metal wires at
the ends of each length. Fix the exposed
parts of two wires to the cell and the
other two of the bulb as shown in
Fig. 9.3 and Fig. 9.4.
Fig.9.2 (a) Torch bulb and (b) its inside view
Fig.9.3 Electric cell with two wires attached to it
Filament
Terminals
Caution: Never join the two terminals
of the electric cell without connecting
them through a switch and a device
like a bulb. If you do so, the chemicals
in the electric cell get used up very fast
and the cell stops working.
(a)
(b)
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Page 3

95 ELECTRICITY AND CIRCUITS
9
Electricity and Circuits
W
e use electricity for many
easier. For example, we use
electricity to operate pumps that lift
water from wells or from ground level
to the roof top tank. What are other
purposes for which you use electricity?
List some of them in your notebook.
Does your list include the use of
electricity for lighting? Electricity
makes it possible to light our homes,
even after sunset. This helps us to
continue working at night. A power station
provides us with electricity. However, the
supply of electricity may fail or it may not
be available at some places. In such
situations, a torch is sometimes used for
providing light. A torch has a bulb that
lights up when it is switched on. Where
does the torch get electricity from?
9.1. ELECTRIC CELL
Electricity to the bulb in a torch is
provided by the electric cell. Electric cells
are also used in alarm clocks,
and many other devices. Have you ever
carefully looked at an electric cell?  You
might have noticed that it has a small
metal cap on one side and a metal disc
on the other side (Fig. 9.1). Did you
notice a positive (+) sign and a negative
(–) sign marked on the electric cell? The
Fig.9.1 An Electric Cell
metal cap is the positive terminal of the
electric cell. The metal disc is the
negative terminal. All electric cells have
two terminals; a positive terminal and a
negative terminal.
An electric cell produces electricity
from the chemicals stored inside it.
When the chemicals in the electric cell
are used up, the electric cell stops
You might have seen the  danger sign shown here displayed on poles,
electric substations and many other places. It is to warn people that
electricity can be dangerous if not handled properly.  Carelessness in
handling electricity and electric devices can cause severe injuries and
sometimes even death. Hence, you should never attempt to experiment
with the electric wires and sockets. Also remember that the electricity
generated by portable generators is equally dangerous. Use only electric
cells for all activities related to electricity.
Caution
Rationalised 2023-24
96 SCIENCE
producing electricity. The electric cell
then has to be replaced with a new one.
A torch bulb has an outer case of
glass that is fixed on a metallic base
[Fig. 9.2 (a)]. What is inside the glass
case of the bulb?
Activity 1
Take a torch and look inside its bulb.
You can also take out the bulb with the
help of your teacher. What do you
notice? Do you find a thin wire fixed in
the middle of the glass bulb [Fig. 9.2
(b)]? Now switch the torch on and
observe which part of the bulb is
glowing.
The thin wire that gives off light is
called the filament of the bulb. The
filament is fixed to two thicker wires,
which also provide support to it, as
shown in Fig. 9.2 (b). One of these thick
wires is connected to the metal case at
the base of the bulb [Fig. 9.2 (b)].  The
other thick wire is connected to the
metal tip at the centre of the base. The
base of the bulb and the metal tip of the
base are the two terminals of the bulb.
These two terminals are fixed in such a
way that they do not touch each other.
The electric bulbs used at home also
have a similar design.
Thus, both the electric cell and the
bulb have two terminals each. Why do
they have these two terminals?
9.2 A BULB CONNECTED TO
AN ELECTRIC CELL
Let us try to make an electric bulb light
up using an electric cell.  How do we do
that?
Activity 2
Take four lengths of electric wire with
differently coloured plastic coverings.
Remove a little of the plastic covering
from each length of wire at the ends.
This would expose the metal wires at
the ends of each length. Fix the exposed
parts of two wires to the cell and the
other two of the bulb as shown in
Fig. 9.3 and Fig. 9.4.
Fig.9.2 (a) Torch bulb and (b) its inside view
Fig.9.3 Electric cell with two wires attached to it
Filament
Terminals
Caution: Never join the two terminals
of the electric cell without connecting
them through a switch and a device
like a bulb. If you do so, the chemicals
in the electric cell get used up very fast
and the cell stops working.
(a)
(b)
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97 ELECTRICITY AND CIRCUITS
Write 'Yes' or 'No' for each arrangement
Now, carefully look at the
arrangements in which the bulb glows.
Compare these with those in which the
bulb does not glow. Can you find the
reason for the difference?
Keep the tip of your pencil on the
wire near one terminal of the electric cell
for the arrangment in Fig. 9.5 (a). Move
the pencil along the wire all the way to
the bulb. Now, from the other terminal
of the bulb, move along the other wire
connected to the cell. Repeat this
exercise for all the other arrangements
in Fig. 9.5. Did the bulb glow for the
arrangements in which you could not
move the pencil from one terminal to
the other?
You can stick the wires to the bulb
with the tape used by electricians. Use
rubber bands or tape to fix the wires to
the cell.
Now, connect the wires fixed to the
bulb with those attached to the cell in
six different ways as have been shown in
Fig. 9.5 (a) to (f). For each arrangement,
find out whether the bulb glows or not.
(d) (e)       (f)
Fig.9.5 Different arrangements of electric cell and bulb
(a)                                            (b) (c)
Fig.9.4 Bulb connected to two wires
Rationalised 2023-24
Page 4

95 ELECTRICITY AND CIRCUITS
9
Electricity and Circuits
W
e use electricity for many
easier. For example, we use
electricity to operate pumps that lift
water from wells or from ground level
to the roof top tank. What are other
purposes for which you use electricity?
List some of them in your notebook.
Does your list include the use of
electricity for lighting? Electricity
makes it possible to light our homes,
even after sunset. This helps us to
continue working at night. A power station
provides us with electricity. However, the
supply of electricity may fail or it may not
be available at some places. In such
situations, a torch is sometimes used for
providing light. A torch has a bulb that
lights up when it is switched on. Where
does the torch get electricity from?
9.1. ELECTRIC CELL
Electricity to the bulb in a torch is
provided by the electric cell. Electric cells
are also used in alarm clocks,
and many other devices. Have you ever
carefully looked at an electric cell?  You
might have noticed that it has a small
metal cap on one side and a metal disc
on the other side (Fig. 9.1). Did you
notice a positive (+) sign and a negative
(–) sign marked on the electric cell? The
Fig.9.1 An Electric Cell
metal cap is the positive terminal of the
electric cell. The metal disc is the
negative terminal. All electric cells have
two terminals; a positive terminal and a
negative terminal.
An electric cell produces electricity
from the chemicals stored inside it.
When the chemicals in the electric cell
are used up, the electric cell stops
You might have seen the  danger sign shown here displayed on poles,
electric substations and many other places. It is to warn people that
electricity can be dangerous if not handled properly.  Carelessness in
handling electricity and electric devices can cause severe injuries and
sometimes even death. Hence, you should never attempt to experiment
with the electric wires and sockets. Also remember that the electricity
generated by portable generators is equally dangerous. Use only electric
cells for all activities related to electricity.
Caution
Rationalised 2023-24
96 SCIENCE
producing electricity. The electric cell
then has to be replaced with a new one.
A torch bulb has an outer case of
glass that is fixed on a metallic base
[Fig. 9.2 (a)]. What is inside the glass
case of the bulb?
Activity 1
Take a torch and look inside its bulb.
You can also take out the bulb with the
help of your teacher. What do you
notice? Do you find a thin wire fixed in
the middle of the glass bulb [Fig. 9.2
(b)]? Now switch the torch on and
observe which part of the bulb is
glowing.
The thin wire that gives off light is
called the filament of the bulb. The
filament is fixed to two thicker wires,
which also provide support to it, as
shown in Fig. 9.2 (b). One of these thick
wires is connected to the metal case at
the base of the bulb [Fig. 9.2 (b)].  The
other thick wire is connected to the
metal tip at the centre of the base. The
base of the bulb and the metal tip of the
base are the two terminals of the bulb.
These two terminals are fixed in such a
way that they do not touch each other.
The electric bulbs used at home also
have a similar design.
Thus, both the electric cell and the
bulb have two terminals each. Why do
they have these two terminals?
9.2 A BULB CONNECTED TO
AN ELECTRIC CELL
Let us try to make an electric bulb light
up using an electric cell.  How do we do
that?
Activity 2
Take four lengths of electric wire with
differently coloured plastic coverings.
Remove a little of the plastic covering
from each length of wire at the ends.
This would expose the metal wires at
the ends of each length. Fix the exposed
parts of two wires to the cell and the
other two of the bulb as shown in
Fig. 9.3 and Fig. 9.4.
Fig.9.2 (a) Torch bulb and (b) its inside view
Fig.9.3 Electric cell with two wires attached to it
Filament
Terminals
Caution: Never join the two terminals
of the electric cell without connecting
them through a switch and a device
like a bulb. If you do so, the chemicals
in the electric cell get used up very fast
and the cell stops working.
(a)
(b)
Rationalised 2023-24
97 ELECTRICITY AND CIRCUITS
Write 'Yes' or 'No' for each arrangement
Now, carefully look at the
arrangements in which the bulb glows.
Compare these with those in which the
bulb does not glow. Can you find the
reason for the difference?
Keep the tip of your pencil on the
wire near one terminal of the electric cell
for the arrangment in Fig. 9.5 (a). Move
the pencil along the wire all the way to
the bulb. Now, from the other terminal
of the bulb, move along the other wire
connected to the cell. Repeat this
exercise for all the other arrangements
in Fig. 9.5. Did the bulb glow for the
arrangements in which you could not
move the pencil from one terminal to
the other?
You can stick the wires to the bulb
with the tape used by electricians. Use
rubber bands or tape to fix the wires to
the cell.
Now, connect the wires fixed to the
bulb with those attached to the cell in
six different ways as have been shown in
Fig. 9.5 (a) to (f). For each arrangement,
find out whether the bulb glows or not.
(d) (e)       (f)
Fig.9.5 Different arrangements of electric cell and bulb
(a)                                            (b) (c)
Fig.9.4 Bulb connected to two wires
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98 SCIENCE
9.3 AN ELECTRIC CIRCUIT
In Activity 2 you connected one terminal
of the electric cell to the other terminal
through wires passing to and from the
electric bulb. Note that in the
arrangements shown in Fig. 9. 5 (a) and
(f), the two terminals of the electric cell
were connected to two terminals of the
bulb. Such an arrangement is an
example of an electric circuit. The electric
circuit provides a complete path for
electricity to pass (current to flow)
between the two terminals of the electric
cell. The bulb glows only when current
flows through the circuit.
In an electric circuit, the direction of
current is taken to be from the positive
to the negative terminal of the electric
cell as shown in Fig.9.6. When the
An electric bulb may fuse due to
many reasons. One reason for a bulb to
fuse is a break in its filament. A break
in the filament of an electric bulb means
a break in the path of the current
between the terminals of the electric cell.
Therefore, a fused bulb does not light
up as no current passes through its
filament.
Can you now explain why the bulb
did not glow when you tried to do so
with the arrangements shown in
Fig. 9.5 (b), (c), (d) and (e)?
Now we know how to make a bulb
light up using an electric cell. Would
you like to make a torch for yourself?
Activity 3
Take a torch bulb and a piece of wire.
Remove the plastic covering at the two
ends of the wire as you did before. Wrap
one end of a wire around the base of an
electric bulb as shown in Fig. 9.7. Fix
the other end of the wire to the negative
terminal of an electric cell with a rubber
band.  Now, bring the tip of the base of
the bulb, that is, its other terminal in
contact with the positive terminal of the
terminals of the bulb are connected with
that of the electric cell by wires, the
current passes through the filament of
the bulb. This makes the bulb glow.
Sometimes an electric bulb does not
glow even if it is connected to the cell.
This may happen if the bulb has fused.
Look at a fused bulb carefully. Is the
filament inside it intact?
Fig.9.6  Direction of current in an electric
circuit
Rationalised 2023-24
Page 5

95 ELECTRICITY AND CIRCUITS
9
Electricity and Circuits
W
e use electricity for many
easier. For example, we use
electricity to operate pumps that lift
water from wells or from ground level
to the roof top tank. What are other
purposes for which you use electricity?
List some of them in your notebook.
Does your list include the use of
electricity for lighting? Electricity
makes it possible to light our homes,
even after sunset. This helps us to
continue working at night. A power station
provides us with electricity. However, the
supply of electricity may fail or it may not
be available at some places. In such
situations, a torch is sometimes used for
providing light. A torch has a bulb that
lights up when it is switched on. Where
does the torch get electricity from?
9.1. ELECTRIC CELL
Electricity to the bulb in a torch is
provided by the electric cell. Electric cells
are also used in alarm clocks,
and many other devices. Have you ever
carefully looked at an electric cell?  You
might have noticed that it has a small
metal cap on one side and a metal disc
on the other side (Fig. 9.1). Did you
notice a positive (+) sign and a negative
(–) sign marked on the electric cell? The
Fig.9.1 An Electric Cell
metal cap is the positive terminal of the
electric cell. The metal disc is the
negative terminal. All electric cells have
two terminals; a positive terminal and a
negative terminal.
An electric cell produces electricity
from the chemicals stored inside it.
When the chemicals in the electric cell
are used up, the electric cell stops
You might have seen the  danger sign shown here displayed on poles,
electric substations and many other places. It is to warn people that
electricity can be dangerous if not handled properly.  Carelessness in
handling electricity and electric devices can cause severe injuries and
sometimes even death. Hence, you should never attempt to experiment
with the electric wires and sockets. Also remember that the electricity
generated by portable generators is equally dangerous. Use only electric
cells for all activities related to electricity.
Caution
Rationalised 2023-24
96 SCIENCE
producing electricity. The electric cell
then has to be replaced with a new one.
A torch bulb has an outer case of
glass that is fixed on a metallic base
[Fig. 9.2 (a)]. What is inside the glass
case of the bulb?
Activity 1
Take a torch and look inside its bulb.
You can also take out the bulb with the
help of your teacher. What do you
notice? Do you find a thin wire fixed in
the middle of the glass bulb [Fig. 9.2
(b)]? Now switch the torch on and
observe which part of the bulb is
glowing.
The thin wire that gives off light is
called the filament of the bulb. The
filament is fixed to two thicker wires,
which also provide support to it, as
shown in Fig. 9.2 (b). One of these thick
wires is connected to the metal case at
the base of the bulb [Fig. 9.2 (b)].  The
other thick wire is connected to the
metal tip at the centre of the base. The
base of the bulb and the metal tip of the
base are the two terminals of the bulb.
These two terminals are fixed in such a
way that they do not touch each other.
The electric bulbs used at home also
have a similar design.
Thus, both the electric cell and the
bulb have two terminals each. Why do
they have these two terminals?
9.2 A BULB CONNECTED TO
AN ELECTRIC CELL
Let us try to make an electric bulb light
up using an electric cell.  How do we do
that?
Activity 2
Take four lengths of electric wire with
differently coloured plastic coverings.
Remove a little of the plastic covering
from each length of wire at the ends.
This would expose the metal wires at
the ends of each length. Fix the exposed
parts of two wires to the cell and the
other two of the bulb as shown in
Fig. 9.3 and Fig. 9.4.
Fig.9.2 (a) Torch bulb and (b) its inside view
Fig.9.3 Electric cell with two wires attached to it
Filament
Terminals
Caution: Never join the two terminals
of the electric cell without connecting
them through a switch and a device
like a bulb. If you do so, the chemicals
in the electric cell get used up very fast
and the cell stops working.
(a)
(b)
Rationalised 2023-24
97 ELECTRICITY AND CIRCUITS
Write 'Yes' or 'No' for each arrangement
Now, carefully look at the
arrangements in which the bulb glows.
Compare these with those in which the
bulb does not glow. Can you find the
reason for the difference?
Keep the tip of your pencil on the
wire near one terminal of the electric cell
for the arrangment in Fig. 9.5 (a). Move
the pencil along the wire all the way to
the bulb. Now, from the other terminal
of the bulb, move along the other wire
connected to the cell. Repeat this
exercise for all the other arrangements
in Fig. 9.5. Did the bulb glow for the
arrangements in which you could not
move the pencil from one terminal to
the other?
You can stick the wires to the bulb
with the tape used by electricians. Use
rubber bands or tape to fix the wires to
the cell.
Now, connect the wires fixed to the
bulb with those attached to the cell in
six different ways as have been shown in
Fig. 9.5 (a) to (f). For each arrangement,
find out whether the bulb glows or not.
(d) (e)       (f)
Fig.9.5 Different arrangements of electric cell and bulb
(a)                                            (b) (c)
Fig.9.4 Bulb connected to two wires
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98 SCIENCE
9.3 AN ELECTRIC CIRCUIT
In Activity 2 you connected one terminal
of the electric cell to the other terminal
through wires passing to and from the
electric bulb. Note that in the
arrangements shown in Fig. 9. 5 (a) and
(f), the two terminals of the electric cell
were connected to two terminals of the
bulb. Such an arrangement is an
example of an electric circuit. The electric
circuit provides a complete path for
electricity to pass (current to flow)
between the two terminals of the electric
cell. The bulb glows only when current
flows through the circuit.
In an electric circuit, the direction of
current is taken to be from the positive
to the negative terminal of the electric
cell as shown in Fig.9.6. When the
An electric bulb may fuse due to
many reasons. One reason for a bulb to
fuse is a break in its filament. A break
in the filament of an electric bulb means
a break in the path of the current
between the terminals of the electric cell.
Therefore, a fused bulb does not light
up as no current passes through its
filament.
Can you now explain why the bulb
did not glow when you tried to do so
with the arrangements shown in
Fig. 9.5 (b), (c), (d) and (e)?
Now we know how to make a bulb
light up using an electric cell. Would
you like to make a torch for yourself?
Activity 3
Take a torch bulb and a piece of wire.
Remove the plastic covering at the two
ends of the wire as you did before. Wrap
one end of a wire around the base of an
electric bulb as shown in Fig. 9.7. Fix
the other end of the wire to the negative
terminal of an electric cell with a rubber
band.  Now, bring the tip of the base of
the bulb, that is, its other terminal in
contact with the positive terminal of the
terminals of the bulb are connected with
that of the electric cell by wires, the
current passes through the filament of
the bulb. This makes the bulb glow.
Sometimes an electric bulb does not
glow even if it is connected to the cell.
This may happen if the bulb has fused.
Look at a fused bulb carefully. Is the
filament inside it intact?
Fig.9.6  Direction of current in an electric
circuit
Rationalised 2023-24
99 ELECTRICITY AND CIRCUITS
a drawing pin into the ring at one
end of the safety pin and fix it on the
thermo Col sheet as shown in Fig. 9.8.
Make sure that the safety pin can be
rotated freely. Now, fix the other drawing
pin on the thermo Col sheet in a way
that the free end of the safety pin can
touch it. The safety pin fixed in this way
would be your switch in this activity.
Paheli has another
arrangement of the cell
and the bulb.  Will the
torch bulb glow in
the following
arrangement?
Fig. 9.9 An electric circuit with a switch
Fig. 9.10 A switch in ‘on’ position Fig. 9.8 A simple switch
Now, make a circuit by connecting
an electric cell and a bulb with this
switch as shown in Fig. 9.9. Rotate the
safety pin so that its free end touches
the other drawing pin. What do you
observe? Now, move the safety pin away.
Does the bulb continue to glow?
The safety pin covered the gap
between the drawing pins when
you made it touch two of them. In
this position the switch is said to be 'on'
(Fig. 9.10). Since the material of the
safety pin allows the current to pass
cell.  Does the bulb glow? Now move the
bulb away from the terminal of the
electric cell. Does the bulb remain
lighted? Is this not similar to what you
do when you switch your torch on or
off?
9.4 ELECTRIC SWITCH
We had an arrangement for switching
on or off our home made torch by
moving the base of the bulb away from
the tip of the cell. This was a simple
switch, but, not very easy to use. We
can make another simple and easier
switch to use in our circuit.
Activity 4
You can make a switch using two
drawing pins, a safety pin (or a paper
clip), two wires and a small sheet of
thermo Col or a wooden board. Insert
Rationalised 2023-24
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## FAQs on NCERT Textbook: Electricity & Circuits - Science & Technology for UPSC CSE

 1. What is electricity?
Ans. Electricity is the flow of electric charge. It is a form of energy that results from the movement of charged particles, such as electrons or ions.
 2. What are circuits?
Ans. A circuit is a complete path through which electric current flows. It consists of a source of electricity, such as a battery, wires or conductors, and devices that use the electrical energy, such as light bulbs or motors.
 3. How does an electric current flow in a circuit?
Ans. An electric current flows in a circuit when there is a potential difference or voltage between two points in the circuit. The current flows from the point of higher potential to the point of lower potential, through the wires and devices in the circuit.
 4. What is resistance in a circuit?
Ans. Resistance is the property of a material that opposes the flow of electric current. It is measured in ohms and depends on the type of material, its length, and its cross-sectional area. Devices such as resistors are used in circuits to provide controlled amounts of resistance.
 5. How do switches work in a circuit?
Ans. Switches are devices that can be used to open or close a circuit. When a switch is closed, it completes the circuit and allows current to flow through it. When a switch is open, it breaks the circuit and no current flows. Switches can be used to control the flow of current in a circuit and turn devices on or off.

## Science & Technology for UPSC CSE

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