1. ENERGY AND ELECTRICITY
In this topic we will learn about:
The different types of energy.
The unit we use to measure energy.
The unit we use to measure power.
Can energy be destroyed?
What do we call the electrical energy that is not used usefully?
Do you use a voltmeter in series or parallel?
What can resistance be used for?
Energy resources.

2. ENERGY Basic facts about energy:
Everything needs energy to do anything.
Energy is measured in Joules.
Energy cannot be made or destroyed.
Energy can be moved from one place to another (transferred).
Energy can change form (transformed).
Energy is sometimes wasted when it is transferred or transformed.

3. TYPES OF ENERGY Energy can exist in the following forms:
Thermal (heat)
Light
Sound
Electrical
Kinetic (movement)
Potential (stored):-
Gravitational – in something that can fall.
Elastic – in something that is stretched, compressed, bent or wound up.
Chemical – in foods, fuels and batteries.
Atomic – used in nuclear reactions.

4. ENERGY TRANSFORMATION
We can use energy flow diagrams to show energy changes.
Chemical energy stored in the battery is converted to electrical energy.
This electrical energy is converted to heat energy in the bulb.
When the bulb is hot enough it will produce light.
Torch battery to bulb.
light
chemical
electrical
heat
This is the INPUT –
the energy we
put in.
This is the OUTPUT –
the energy we want to
get out.

5. ENERGY AND ELECTRICITY
We can use energy flow diagrams to show wasted energy too.
In the torch bulb, not all of the heat energy is transformed into light.
light
chemical
electrical
heat
heat
This is
wasted

6. ENERGY AND ELECTRICITY
Energy is wasted as heat whenever energy changes its form, an even better diagram would look like the one below.
It shows that energy is lost at every stage.
light
chemical
electrical
heat
heat
In the battery.
This is
wasted
This is
wasted
heat
In the wiring.
heat
Given to the surroundings.
This is
wasted
The thickness of the arrows shows how much energy is being transferred or wasted.

7. ELECTRICAL ENERGY
One of the most useful forms of energy is electrical energy.
It is a convenient way of moving energy from one place to another.
Electrical charges have to be given energy before they can move around a circuit as an electric current.
The battery (or mains supply) gives energy to the charges.
This energy allows the charges to move.
The more energy they are given, the bigger the current is.

8. VOLTAGE
The voltage of an electricity supply tells you how much energy the battery can give to each charge.
Voltage is measured in Volts (V)
What will happen to the current in a circuit if the voltage supply is decreased?
Decreasing the voltage will give the charges less energy.
This means the current will be smaller.

9. MEASURING VOLTAGE
In a circuit, there is a voltage across each component, (a component is something like a bulb).
A voltmeter is used to measure voltage.
The voltmeter has to be placed around (in parallel with) the component.
The voltmeter is measuring the ‘voltage across the component’. V

10. SHARING VOLTAGE IN A SERIES CIRCUIT
In a series circuit, the supply voltage is shared between the components in the circuit.
This is because the charges have to pass through all the components as they pass around the circuit. 6V 6V 2V

11. USING VOLTAGE
The brightness of a bulb in a circuit depends on how much voltage it gets.
Remember - in a series circuit, the supply voltage is shared between the components in the circuit.
This means that adding bulbs in series will make each bulb dimmer. 6V
normal 6V
2V very dim

12. VOLTAGE IN A PARALLEL CIRCUIT
In a parallel circuit, each charge only travels through one arm of the circuit.
Because of this, each arm gets the full supply voltage.
This means bulbs in parallel will be brighter.
12V
12V bright
12V
12V normal X
When the charges get to X, some go along the green path and some go along the blue path. Each charge only uses one path.
The charges have only
one route to take.

13. VOLTAGE QUESTIONS
Each cell in the diagrams below has a voltage of 1.5V.
What will be the voltage across each bulb?
The first one is done for you.
1.5V

14. VOLTAGE ANSWERS The voltages across each bulb are shown below:
In a series circuit you need to work out the total supply voltage then divide that between the number of bulbs it is shared between.
1.5V 3V
Each bulb gets 1V.

15. PARALLEL PROBLEMS
Each cell in the diagrams below has a voltage of 1.5V Work out the voltage across each bulb in these circuits.

16. PARALLEL PROBLEMS SOLVED
Remember each arm will get the full supply voltage.
1.5V
0.75V
1.5V
1.5V 3V
1.5V 3V
The voltage each arm gets
is shared between the
components in that arm.

17. RESISTANCE Real circuits do not just contain bulbs.
They may contain resistors.
The voltage will be shared between resistors in series in the same way as it is for bulbs in series.
If the resistors are of different sizes, the bigger resistor will use a greater share of the supply voltage.
Remember that all parts of a circuit – including bulbs and even the wires – have resistance
Circuit symbol for a resistor.
Resistance causes heat.
This is useful in an electric heater.

18. ELECTRICITY IN OUR HOMES
Most of the electricity we use at home comes from the mains supply. This is supplied by energy providers.
The voltage of the mains supply is 240V.
Mains electricity carries a lot of energy.
It needs to carry a lot of energy because the electrical equipment we use at home needs energy to work.
The power rating of an electrical appliance tells you how much energy it uses every second.
Power is measured in Watts (W).

19. USING POWER
The higher the power of an appliance, the more it costs to run.
Different electrical appliances use different amounts of power.
As a guide :
Using electricity for lighting uses low power.
Using electricity for movement uses medium power.
Using electricity for heating uses high power.

20. POWER PROBLEMS
Do these appliances use low, medium or high power?

21. SOLUTIONS TO POWER PROBLEMS
High
Medium
Medium
Low
Medium
High
High
Low

22. ENERGY AND ELECTRICITY
Most of our electricity is made in power stations.
In most power stations, fossil fuels are burned.
The heat produced is used to boil water and turn it into steam.
The steam then moves and turns a turbine.
The turbine is connected to a generator.
The generator makes electricity.
Fuels
burned.
Water turns
to steam.
Steam turns
turbines.
Turbines turn
generators.
Generators make
electricity.
The electricity is then sent around the country to wherever it is needed.
How else can electricity be made?

23. RENEWABLE ENERGY SOURCES
Some other possibilities are:
Renewable fuels such as biomass or wood could be burned to boil water and turn it into steam.
Nuclear fuels can be used to make the heat needed to boil water and turn it into steam.
Wind, waves and tides turn turbines which then operate generators.
With geothermal energy natural steam can be used to turn turbines.

24. Check your learning What is the unit we use to measure energy?
What is the unit we use to measure Power?
Can energy be destroyed?
What do we call the electrical energy that is not used usefully?
Do you use a voltmeter in series or parallel?
What can resistance be used for?

25. Check your learning - answers
ENERGY is measure in JOULES.
POWER is measure in WATTS.
ENERGY can not be destroyed just changed from one form to another.
Electrical energy that is not used usefully is called WASTED energy.
VOLTMETERS are always used in PARALLEL.
RESISTANCE can be used to heat up wires in ELECTRIC HEATERS.