Lss module 1 chpt 4 investigating electricity

MODULE 1:
GADGETS WORK WONDERS (I)
Chapter 4 Investigating Electricity
1© Copyright Star Publishing Pte Ltd

4.1 Why is electricity a useful form of
energy?
4.2 Why are electrical appliances made of
both conductors and insulators?
4.3 What are current, voltage and
resistance?
4.4 What are the differences between
series and parallel circuits?
4.5 How can electricity be used safely and
responsibly?

Objectives
 Describe electricity as a useful form of
energy in our life
 Outline the process from the
production of electricity to using it in
our home with reference to the energy
conversions that take place

Why is electricity a Useful Form of
Energy? Electricity is useful as it
provides energy for
electrical appliances.
 Electricity is used widely
as:
(a) it can be transmitted
from one place to
another easily using
wires and cables.
(b) Electricity can be
converted to other
forms of energy
electrical appliances

How is electrical energy converted to
heat energy?
 We need different forms of
energy for different
purposes.
 Electrical appliances
convert electricity into the
form of energy we need.
 When we need heat energy,
we use appliances such as
electric kettles and electric
irons.
© Copyright Star Publishing Pte Ltd 5
appliances that convert
electrical energy to heat energy
Activity Book Link
Activity 4.1
Importance of Electricity
Activity 4.2
Using Electricity to Produce Heat

light and/or sound energy?
 Electricity provides
us with lighting
such as by using
appliances such as
fluorescent
lamps.
 Appliances like
televisions and
audio systems
convert electricity
to light and/or
sound energy.
electrical appliances that convert electrical
energy to light and/or sound

mechanical energy?
 Washing machines, blenders and electric fans
have electric motors that convert electricity to
mechanical energy.
electrical appliances that convert electrical energy
into mechanical energy

Gadgets and electricity
 Mobile phones, portable music
players, laptop computers operate
on electricity.
handphone
computer

What are the Sources of Electricity?
 In Singapore, most of the electricity is produced
at the power stations.
 The power stations in Singapore use fossil fuels
(oil and natural gas) to produce electricity.
the Senoko Power Station is located at the northern
part of Singapore

What are the energy conversions in a
Power Station?

How is electricity distributed to homes
and offices?

What are other Sources of
Electricity?
 Electricity can also be obtained from
batteries which provide us with electrical
energy while we are on the move.
different types of batteries

Solar energy
 Some rural areas are too
far out to receive
electricity from power
stations and depend on
solar energy.
 Solar panels on top of
some buildings provide
electricity.
 However, they provide a
limited amount of
electricity.
solar panels provide electricity
in rural areas
Solar panels installed on top
of buildings
Activity Book Link
Activity 4.4
How Electricity is Produced

energy?
4.2 Why are electrical appliances made
of both conductors and insulators?
resistance?
responsibly?

Objectives
 Relate the electrical conducting
properties of materials to their use in
the various parts of electrical
appliances/circuits
 Investigate and classify a variety of
materials as insulators or conductors

Electrical conductors and insulators
 Materials can be classified into electrical
conductors and electrical insulators.
electricity does not pass
through every part of a hairdryer
copper is commonly
used to make wires

What are electrical
conductors?
 Electrical
conductors are
materials that allow
electricity to pass
through them.
 The most common
conductors are
metals such as
copper and
aluminium. © Copyright Star Publishing Pte Ltd 17
aluminium is used to
make power lines

What are electrical insulators?
 Electrical
insulators are
materials that do
not allow
electricity to pass
through them.
 Examples are
plastics, rubber,
wood, glass and
paper.

Are there non-metals that conduct
electricity?
 Examples of non-
metals that conduct
electricity is
graphite, a form of
carbon found in
pencil lead.
 Acids and salt
solutions are other
examples of non-
metals that conduct
electricity
examples of non-
metals
that conduct
electricity

Using Electrical Conductors and
Insulators
 We can find both
conductors and
insulators in electrical
appliances.
 Conductors are used to
conduct electricity so
that electrical appliances
can function.
 Insulators are used to
prevent electricity from
flowing to places that we
do not want it to reach.
a hairdryer is
made of both
conductors and
insulators
copper wires are
insulated with
plastic covers
Activity Book Link
Activity 4.5
Electrical Conductors and Insulators

energy?
resistance?
responsibly?

Objectives
 Explain what is meant by current,
voltage and resistance and state their
units
 Use a voltmeter/ammeter for electrical
measurements

What is Current?
 In the above, the bulb lights up because there
is an electric current flowing from the
positive (+) terminal of the battery to the
negative (–) terminal
current in the circuit causes
the bulb to light up

How do we measure current?
 We measure current with an
ammeter.
 Ammeters should be connected in
series.
 The ammeter has two terminals:
(a) The positive terminal should be
connected to the positive terminal of
the battery.
(b) The negative terminal should
be connected nearer to the negative
terminal of the battery.
an ammeter

What is SI unit of electric current?
 The SI unit of electric current is the ampere (A).
 A current of 2 amperes is written as 2 A.
Activity Book Link
Activity 4.6
Measuring Current

What is voltage?
 Voltage provides the
energy for current to
flow
 We can understand
voltage by thinking of a
water pump pumping
water around a circular
pipe. When the pump is
removed, the water
stops flowing.
a water pump pumps water around a
circular pipe
a dry cell provides energy for
current to flow

How do we measure voltage?
 To measure the
voltage between
two points in an
electric circuit,
an instrument
called the
voltmeter is
used.
 Voltmeters
should be
connected in
parallel.
voltmeters are connected
in parallel

What is the SI unit of voltage?
 The SI unit of voltage is the volt (V).
 A voltage of 1.5 volts is written as 1.5
V.
Activity Book Link
Activity 4.7
Measuring Voltage
Activity 4.8
Voltage and Current

Cells in series
 A common dry
cell usually
provides 1.5 V
of voltage.
 To get a higher voltage,
we can join two or more
dry cells by connecting
the ‘+’ terminal of a cell to
the ‘–’ terminal of another
cell as shown below.

What is Resistance?
 Resistance is
something that
opposes the flow of
current.
 All electrical
components have
resistance.
 Some components
have higher resistance
than others.
copper wires have very
low resistance
light bulbs have
higher resistance

How is resistance related to
the current?
 The higher the resistance in a circuit, the
smaller the current.
 Circuit A has a higher resistance than Circuit
B, therefore the current in Circuit A is smaller.

What is resistance?
 Water flows
quickly when there
is nothing to block
it (low resistance)
 Water flows slower
when there is
something
blocking it (high
resistance)
 We can better understand resistance by
looking at how water flows.

What is a resistor?
 A resistor is an electrical
component that provides
resistance.
 There are two types of
resistors — fixed resistor
and variable resistor.
 The resistance of a fixed
resistor cannot be
changed.
 The resistance of a
variable resistor can be
adjusted, usually by
turning a knob or moving
a slider.
a fixed resistor
two types of variable resistors

How do we measure
resistance?
 Resistance can be
measured using a
multimeter set to
resistance mode.
 The SI unit of resistance
is the ohm (Ω).
 A resistance of 10 ohms
is written as 10 Ω.
a multimeter can be
used to measure resistance.

What are the uses of
resistors?
 Resistors are
widely used in
electrical
appliances such
as radios,
televisions, and
computers to
obtain the current
needed for them
to work properly.
resistors adjust current flowing
through appliances

energy?
resistance?
responsibly?

Objectives
 Identify series and parallel circuits
 Explain why parallel circuits are widely
used in household while series circuits
are not
 Draw and interpret circuit diagrams
and set up circuits comprising
electrical sources (cell and battery),
switches, lamps, resistors (fixed),
ammeters and voltmeters

What is an electric circuit?
 An electric circuit is a path for
current to flow.
current flows through an electric circuit

Open and closed circuits
 an open circuit with
no current
 a closed circuit
with current
 Current will only flow in a closed circuit.

What is a series circuit?
 In a series circuit, the electric components are
connected as a single path.
 If one of the bulbs is removed or blown, the circuit will
be opened. The other two bulbs will not light up.
 This is why it is not advisable to connect the lights in our
homes in series.
a series circuit

What is a series circuit?
 Traffic flows on an
one-lane bridge
 Traffic stops when
one part of a bridge
collapses
 A series circuit is like a bridge with only
one lane.
 When one part of the bridge collapses, the
traffic will stop.

What is a parallel circuit?
 In a parallel circuit, the
electrical components are
connected to form two or
more paths.
 When one of the bulbs is
removed or blown, the
other two bulbs will not
be affected.
 This is why the lights in
our homes are connected
in parallel.
a parallel circuit

What is a parallel circuit?
 A parallel circuit is like a road with two
separate lanes. When one of the lanes is
blocked, traffic can still pass through the
other lane.
traffic continues on the lane that is not blocked

Circuit Symbols
 To make drawing of electrical circuits simple,
symbols representing electric parts are used.

Circuit diagrams
 a circuit with a cell,
two bulbs
connected in
series and an
open switch
 a circuit with a cell,
two bulbs
connected in
parallel and a
closed switch
Activity Book Link
Activity 4.9
Electric Circuits

energy?
resistance?
4.5 How can electricity be used safely
and responsibly?

Objectives
 State the hazards of using electricity in
the following situations:
▲Damaged insulation
▲Overloaded circuits
▲Damp conditions
 List some precautionary measures to
ensure the safe use of electricity
 State the importance of reducing
electrical energy wastage
 Appreciate the importance of using
electrical energy responsibly and safely

What are the Hazards of Using
Electricity?
 Electricity, if it is not
used properly,
electricity can
cause harm or
even kill.
 The voltage of our
mains is 230 V.
This is considered
a high voltage that
is dangerous.
the mains supply in Singapore is 230 V.

Common electrical hazards
 There are three common electrical
hazards:
(a) damaged insulation,
(b) overloaded circuits, and
(c) damp conditions.

Electrical hazards

Safety Features
 There are safety features in our home
electrical system to protect us against the
dangers of electricity.
circuit breakers cut off
electricity to the
house (or part of the
house) when the current
becomes too big
fuses melt and cut off
electricity to electrical
appliances when the
current becomes too
big
earth wires protect us
against electric shock
when the metal casing
of an electrical
appliance
comes in contact with a
high voltage

Why is it important to reduce
Electrical Energy Wastage?
 It is important for us to reduce wastage of
electricity energy because:
(a) Singapore depends heavily on fossil
fuels imported from other countries to
produce electricity;
(b) fossil fuels will be gone forever once
they are used;
(c) burning of fossil fuels causes
pollution.

What are ways to reduce wastage
of electrical energy?
 Use energy saving lamps instead of filament
lamps.
 Use natural light and ventilation
 Use electric fans instead of air conditioners.
 Choose appliances which are energy efficient
 Find out the electrical appliances that use a lot
of energy and reduce the time they are used.
an energy saving lamp

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