This presentation is for classes 7 and 6 to know about electricity. It is important these days we use electricity for many purposes . It was discover by Hans Christian Oersted . this is having all knowlegde about Electric cell The danger sign Electric bulb Fused bulb Electric components and its symbol Battery Electric circuits Electric torch Drawing an electric circuit diagram Electric switches Heating effect of electric current Production of light Electric fuse Magnetic effect of electric current Conductors and insulators thankyou

1. -YOGITA GUPTA
ELECTRIC CURRENT
AND ITS EFFECT

2. INTRODUCTION
o We use electricity for many purposes to make our tasks
easier. For example, we use electricity to operate pumps
that lift water from wells or from ground level to the roof
top tank.
o Electricity makes it possible to light our homes, roads,
offices, markets and factories 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?
o Let us discover what is this term electricity and how does
it works.

3. THE TOPICS WHICH ARE COVERED ARE
 Electric cell
 The danger sign
 Electric bulb
 Fused bulb
 Electric components and
its symbol
 Battery
 Electric circuits
 Electric torch
 Drawing an electric
circuit diagram
 Electric switches
 Heating effect of electric
current
 Production of light
 Electric fuse
 Magnetic effect of
electric current
 Conductors and
insulators

4. o Electricity to the bulb in a torch is
provided by the electric cell.
Electric cells are also used in alarm
clocks, wristwatches, transistor
radios, cameras and many other
devices.
o An electric cell has a positive and a
negative terminal. The metal cap is
the positive terminal of the electric
cell. The metal disc is the negative
terminal. Which is found in dry cell.
An electric cell produces electricity
from the chemicals stored inside it
called electrolyte. When the
chemicals in the electric cell are
used up, the electric cell stops.
ELECTRIC
CELL

5. THE DANGER SIGN
 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.

6. ELECTRIC BULB
 An electric bulb is a device which
produces light when electricity is passed
through its terminals.
 The bulb has two thick contact wires in
the centre with a thin wire attached
between them. This thin wire is
called filament.
 One of the thick wires is connected to the
metal case at the base of the bulb and the
other is connected to the metal tip at the
centre of the base. These two form the
terminals.
 When electricity is passed through the
terminals of the bulb, the filament gets
heated up and produces light.
 The two terminals do not directly touch
each other to avoid short circuit.

7. FUSED BULB
 A fused bulb means a break in
its filament which results in a
break in the path of the current
between the terminals of the
electric cell. Thus a fused
bulb does not light up as no
current passes through its
filament.

8. ELECTRIC COMPONENTS AND ITS
SYMBOL

9. BATTERY
 A battery is a combination of two or more cells
combined in series to produce higher electricity. It is
used in applications where more electricity is
needed like torch, toys, UPS, Car etc.

10. ELECTRIC CIRCUITS
 An electric circuit is a path
along which electricity can
flow. A simple electric
circuit consist of a cell,
torch bulb and two pieces of
wire (called connecting
wires). ... 6) The wires and
bulb form a continuous path
between the two terminals
of the cell for electricity to
flow through.

11. OPEN CIRCUIT AND CLOSED CIRCUIT
 Open circuits : If there is any
gap in the path of a circuit,
the bulb does not light up.
Such a circuit is called an
open circuit.
 Closed circuits : The bulb
lights up only when a bulb
and wire form a complete
path, which starts at one
terminal of electric cell and
ends at the other terminal.
Such a circuit is called a
closed circuit.

12. ELECTRIC TORCH
 A torch contains a simple electric circuit. In
a torch, two (or more) cells are connected to
a torch bulb through a sliding switch. When
the torch is needed to provide light, we close the
sliding switch by pushing it forward so that the
circuit is completed and the bulb lights up.

13. ELECTRIC SWITCHES
 Electric Switch is an
electrical device which can
make or break an electric
circuit.
 A switch is said to be in
‘ON’ position when it
makes or completes the
circuit and allows the
current to pass through.
 Similarly, a switch is in
‘OFF’ position when it
breaks the circuit and does
not allow the current to
pass through.

14. HEATING EFFECT OF ELECTRIC CURRENT 1
 When an electric current passes through a
wire the wire gets heated up. This is known
as the heating effect of electric current.
 The heat that is produced in the wire
depends upon the following factors:
 the material of the wire
 the length of the wire
 the thickness of the wire
 Many appliances work on the heating effect
of electric current such as:
 electric heater
 electric iron
 electric stove
 geysers
 electric coffee maker
 Toaster
 Hair dryer

15. HEATING EFFECT OF ELECTRIC CURRENT 2
 All these elements produce a high amount of heat
when electricity passes through them. However,
this amount can change depending upon the
requirements of the device. This is so because they
contain a coil of wire known as an element.
 Depending upon the amount of heat required by
such appliances different types, sizes and length of
wire are used in them. Some virus can break down
or melt as they get heated.

16. PRODUCTION OF LIGHT IN A BULB DUE TO THE
HEATING EFFECT OF ELECTRIC CURRENT
 The filament of a bulb is a coiled wire that gets hot
when electricity is passed through it. This makes
the filament glow and as a result, light is produced
from the bulb.

17. FUSES
 An electric fuse is a device that is used
to prevent the damage that can be
caused by an excess of electric current.
According to the heating effect of the
electric current, a wire becomes hot as
current is passed through it. However, if
an excess of current is passed through a
wire it can melt or break.
 The electric fuse consists of a wire
which is made up of a metal or an alloy
which has a low melting point. As a
result, the wire breaks down easily as
high current passes through it. As the
wire breaks the circuit of the fuse opens
and hence no for the current passes
through it.
 This can prevent a short circuit for fire
due to high electric current.
 Different types of fuses are used for
different devices and some are also
available for houses as we.

18. HOW CAN EXCESSIVE CURRENT PASS THROUGH A
CIRCUIT?
Reasons why excessive current can pass through a
circuit:
 Sometimes we connect different devices to the
same socket which results in drawing of more
current from that socket. As a result, the load on the
circuit increases and it can lead to a short circuit or
fire.
 When the insulation of wires gets torn away, the
wires can come in contact with each other which
cause a spark or may lead to a fire (short circuit).
 This is why fuses are used to prevent any kind of
short circuit and overloading.

19. CFL
 CFLs do not work on the
heating effect of electric current.
 They do not have a filament
inside them instead they contain
two electrodes that produce
light.
 These bulbs have a fluorescent
coating inside them which
makes the light brighter.
 CFLs thus save energy as they
do not produce heat along with
the light.
 Ordinary bulbs on the other
hand waste energy as they get
heated while lighting up.

20. ISI
 ISI stands for Indian
Standards Institute which
standardizes all electrical
appliances.
 Hence if any appliance does
not have an ISI mark over it, it
means that this appliance
does not conform to the
standard guidelines of ISI and
hence it is not safe to use.
 On the other hand, if any
appliance holds such a mark,
it means that it is safe to use,
it is a quality product and it
will not lead to wastage of
electricity.

21. MINIATURE CIRCUIT BREAKER OR MCB
 A miniature circuit
breaker or MCB is generally
used instead of fuses.
 A fuse breaks due to excessive
current so that the circuit opens
up and the damage can be
prevented. However, once a
fuse breaks down it cannot be
used again.
 MCB, on the other hand, is a
switch which turns OFF on its
own when a circuit overloads.
Once the problem the circuit is
rectified we can switch ON the
MCB once again.

22. MAGNETIC EFFECT OF ELECTRIC CURRENT
 When an electric current is passed through a wire it
behaves like a magnet. This is called the magnetic
effect of the electric current which was discovered
by a scientist, Hans Christian Oersted.
 He discovered that the needle of a compass
deflects when an electric current is passed through
a wire placed near the compass. This indicates that
a magnetic field is created near the wire that
deflects the needle.

24. ELECTROMAGNET
 Every magnetic material has a magnetic field up to
which the influence of its magnetism can be
experienced.
 A magnet whose magnetic field is generated with the
help of electric current is called an Electromagnet.
 The Electromagnet is formed because of the magnetic
effect of the electric current.
 Applications of Electromagnets
 Electromagnets are used in domestic appliances such
as electric bells.
 They are used in toys.
 They are used in all kinds of telecommunication
equipment.
 They are used in cranes to separate magnetic materials
from junk and to lift heavy objects.
 They are used by doctors to remove any magnetic
materials that we have fallen in the eye

26. ELECTRIC BELL
 Components of an Electric Bell
 A coil of wire wound over an iron piece that forms the Electromagnet.
 An iron strip (soft iron armature) which has a hammer attached to it which is
joined to the wire coil.
 A contact screw through which is attached to the iron strip.
 A battery which connects the wire coil and the contact screw.
 A switch in the middle of the circuit.
 Working of an Electric Bell
 When the switch of the Bell is ON, an electric current flows through the coil
of wire which makes the iron piece attached to it act as an Electromagnet.
 As a result, the iron piece attracts the hammer towards itself. The hammer
thus hits the bell and a sound is produced.
 As the hammer move towards the iron piece, it moves away from the
contact screw which breaks down the circuit.
 As the circuit breaks the wire coil stops receiving any current which makes
the electromagnet lose its magnetic effect.
 As a result, the hammer falls back to its original position.
 Then as the hammer falls back the iron strip again comes in contact with
the contact screw and the circuit gets completed.
 This again turns the iron piece into an electromagnet and the whole process
continues until the bell is switched OFF. This results in the continuous
ringing of the bell.

28. CONDUCTORS AND INSULATORS
 Materials which allow electric
current to pass through them are
called conductors of electricity.
Examples are iron nail, key,
safety pin, water, human body
etc.
 Materials which do not allow
electric current to pass through
them are called insulators of
electricity. Examples are rubber,
plastic, glass, air, cloth etc.
 Conductors are mainly metallic
while insulators are non-metallic.
 Electrical devices are made up of
conductors. To avoid passing of
the current to human body during
their handling, these devices
have a covering of insulators (like
plastic, wood, aluminium) over
them.

30. STATE THE PROPERTY OF A
CONDUCTING WIRE IS UTILISED IN
MAKING ELECTRIC FUSE ?
145 3 2

31. EXPLAIN WHY ARE CFLS (COMPACT
FLUORESCENT LAMPS) PREFERRED
OVER ELECTRIC BULBS ?
145 3 2

32. WHEN DOES A CIRCUIT IS
SAID TO BE OVERLOADED?
145 3 2

33. NAME THE SCIENTIST
WHO DISCOVERED
MAGNETIC EFFECT OF
ELECTRIC CURRENT ?
145 3 2

34. WHAT IS AN
ELECTROMAGNET ?
145 3 2

35. WHAT IS ELECTRIC BULB ?
145 3 2

36. EXPLAIN WHAT IS AN
ELECTRIC TORCH ?
145 3 2

37. WHAT IS HEATING EFFECT
OF ELECTRIC CURRENT ?
145 3 2

38. WHAT IS A ELECTRIC SWITCH ?
145 3 2

39. EXPLAIN ELECTRIC FUSE ?
145 3 2

40.  Electric fuse wire is made up of special material
which has low melting point. As if high amount of
current is passed, it melts to disconnect the electric
circuit and prevent us from causing any damage.
 Compact fluorescent lamps are preferred over
electric bulbs because electric bulbs use more
power of electricity and it also losses electrical
energy in the form of heat but it is not so in compact
fluorescent lamps.
 It is overloaded by connecting too many devices to
it. When too many devices get connected, then a
circuit is said to be overloaded.
 The scientist who discovered the magnetic effect of
electric current is Hans Christian Oersted

41.  A magnet whose magnetic field is generated with
the help of electric current is called
an Electromagnet.
 An electric bulb is a device which produces light
when electricity is passed through its terminals.
 A torch contains a simple electric circuit. In
a torch, two (or more) cells are connected to
a torch bulb through a sliding switch. When
the torch is needed to provide light, we close the
sliding switch by pushing it forward so that the
circuit is completed and the bulb lights up.
 When an electric current passes through a wire the
wire gets heated up. This is known as the heating
effect of electric current.

42.  Electric Switch is an electrical device which can make or
break an electric circuit.
 An electric fuse is a device that is used to prevent the
damage that can be caused by an excess of electric
current. According to the heating effect of the electric
current, a wire becomes hot as current is passed
through it. However, if an excess of current is passed
through a wire it can melt or break.
The electric fuse consists of a wire which is made up of a
metal or an alloy which has a low melting point. As a
result, the wire breaks down easily as high current passes
through it. As the wire breaks the circuit of the fuse opens
and hence no for the current passes through it.
This can prevent a short circuit for fire due to high electric
current.
Different types of fuses are used for different devices and
some are also available for houses as we.

43. THANK YOU