CHAPTER 6

SOURCES OF ENERGY

THE VARIOUS FORMS OF ENERGY

1. Energy is the ability to do work.

2. The SI unit for energy is Joule (J).

3. There are various forms of energy.

a) Potential Energy

• Energy stored in an object because of its condition

and position.

• Examples:

i. A rock on top of a hill

ii. The water in the dam

iii. Fruit on a tree

iv. A stretched spring or elastic band

v. A bent ruler

vi. A book on a shelf

b) Kinetic Energy

• Energy possessed by a moving object.

• Examples

i. Flying birds

ii. Running water

iii. Wind

iv. Moving car

v. Spinning fan

vi. Waves

• Energy stored in a hot object.

• Energy that can raise the temperature of an object.

• Examples

i. Burning object v. Boiling water

ii. Lighted match sticks vi. Hot iron

iii. Lighted electric bulbs

iv. The heat from the sun

c) Heat Energy

• Energy from an object that emits light

• Examples

i. Lightning

ii. Fire

iii. Lighted candle

iv. Fire flies

v. Torch

vi. Lighted lamps

d) Light Energy

• Energy that is stored in chemical

substances.

• Examples

i. Chemical substances like batteries,

hydrochloric acid and sodium hydroxide

ii. Foods

iii. Fuels

e) Chemical Energy

• Energy produced by flow of electrical

charges (electric current).

• Examples

i. Dynamos

ii. Lightning

iii. Power stations

iv. Batteries or dry cells

v. Solar cells

f) Electrical Energy

• Energy produced by a vibrating object.

• Examples

i. Beating a drum

ii. Ringing a bell

iii. Thunder

iv. Whistling birds

v. Singing a song

g) Sound Energy

• Also known as atomic energy.

• Energy stored in the nucleus of an

atom.

• Examples

i. Produced by fission and fusion of atoms

ii. Atomic bomb

iii. Nuclear reactor

h) Nuclear Energy

SOURCES OF ENERGY

a) Sun - Solar energy

b) Water - Hydroelectric energy

c) Fossil fuels - Heat energy

d) Biomass fuels - Biomass energy

e) Wind - Wind energy

f) Geothermal sources - Heat energy

g) Radioactive - Nuclear energy

substances

a) Sun

1. Sun is the primary source of energy on Earth.

2. Energy derived from the sun is called Solar

energy.

3. Heat and Light are two forms of solar energy.

4. Solar cells absorbs light energy from the sun

directly and change it into electrical energy.

5. Example: calculators, watches, satellites

6. Solar heater changes energy from the sun

to heat energy to heating up water and

cooking purposes.

1. Electricity generated using water is called

hydroelectricity.

2. Hydroelectricity is produced in power

stations by forcing the water from a dam

to flow and rotate turbines and dynamos.

b) Water

1. Fossil fuels are combustible materials which

means that they burn easily to release heat

and light energy.

2. Examples of fossil fuels:

a) Oil (petroleum and crude oil)

b) Natural gas

c) Coal

3. Fossil fuels provide heat energy to generate

electricity.

c) Fossil Fuels

1. Fuels such as firewood, paddy husks, dry

leaves, animal faeces and household

waste which are biological materials are

known as biomass fuels.

2. These fuels produce biomass energy.

3. Biomass energy is used for working

machines and moving vehicles.

d) Biomass Fuels

1. Wind is moving air which contains kinetic

energy.

2. Wind mills have been used for pumping water,

grinding grains and drive machines.

3. A wind turbine is used to generate electricity

using wind energy.

e) Wind

1. The heat energy from the very hot interior of

the Earth is called geothermal energy.

2. Most of the geothermal areas are near

volcanoes, hot springs and geysers.

3. Geothermal energy produces steam which is

used to drive generators to produce electricity.

f) Geothermal Sources

1. Radioactive substances like Uranium and

Plutonium can be used produce nuclear

energy.

2. Nuclear reactions generate lots of heat

energy that can be used to produce steam

that drives generators to produce electricity.

g) Radioactive Substances

3. This electricity is used for:

i. War ships

ii. Submarines

iii.Satellites

iv.Meteorological stations

v. Light houses

ENERGY CHANGES

1. The principle of conservation of energy

states that energy cannot be created or

destroyed but can be changed from one

form to another.

2. The total amount of energy in the world is

fixed. Total energy before change = total energy after change

3. When a marble rolls down an inclined slope,

potential energy changes into kinetic energy.

*copy the diagram form text book

i. Point A – highest point on the slope

ii. Point C – lowest point on the slope

iii. At point A, the marble has the maximum potential

energy.

iv. When the marble rolls down to point B, it has both

potential energy and kinetic energy.

Potential Energy Kinetic Energy

v. At point C, all of the potential energy has

changed into kinetic energy.

vi. The marble moves faster at point C.

vii.At point C, the marble has maximum

kinetic energy.

4. Example of energy change:

RENEWABLE AND NON - RENEWABLE ENERGY

1. The sources of energy in this world can

be classified into two groups:

a. Renewable Energy Sources

b. Non − renewable Energy Sources

2. Renewable energy sources exists

continuously and can be replenished or

renewed when they have been used.

3. Examples of renewable energy

sources:

a. Sun – solar energy

b. Flowing water – hydroelectric energy

c. Plants – biomass energy

d. Wave – wave energy

e. Wind – wind energy

f. Geothermal resources – geothermal

energy

4. Non – renewable energy sources are that

cannot be replenished or renewed and will

eventually be used up and exhausted.

5. Examples of non – renewable energy

sources:

a) Fossil fuels – petroleum, crude oil, natural

gas and coal

b) Radioactive substances

WAYS TO USE ENERGY EFFICIENTLY 1. Use energy saving electrical appliances

2. Recycle used things such as old

newspapers and plastics

3. Share cars (carpool) or use public

transport such as commuter or LRT

4. Do not leave electrical appliances

switched on when they are not in use

5. Find alternative sources of energy such

as solar energy and wind energy

THE IMPORTANCE OF CONSERVING ENERGY SOURCES

1. Energy sources must be conserved

because half of the energy sources will

be depleted in a 100 – year cycle.

2. Conserving energy sources are

important because:

a. It will reduce the wastage of energy

b. It will enable the non – renewable

energy sources to last longer

c. It will ensure the energy sources last

for the future generations

EXERCISE

1. Circle the names of the objects below

which shows examples of Potential

Energy.Stretched elastic band

Radio

Compressed spring

Solar cell

Wound toy car

2. Draw lines to match the energy converter to its energy change.

Electrical fan ● ● Kinetic energy → Electrical energy

Dynamo ● ● Electrical energy → Kinetic energy

Plants ● ● Light energy → Chemical energy

2. f

3. The diagram below shows four sources of

energy. Name each of the sources of

energy.

P Q R

S

a. P:

b. Q:

c. R:

d. S:

Wind

Fossil FuelNuclear SubstancesWater