What is Energy?
We use energy to do work and make all movements. When we eat, our
bodies transform the food into energy to do work. When we run or walk or
do some work, we ‘burn’ energy in our bodies. Cars,
planes, trolleys, boats, and machinery also transform
energy into work. Work means moving or lifting
something, warming or lighting something. There are
many sources of energy that help to run the various
machines invented by man.
TYPES OF ENERGY
“Energy at rest.”
• An object can store energy
as the result of its position.
• The higher an object is,the
more potential energy it
“Energy of motion.”
• If something is moving it
has kinetic energy.
• The faster an object is
moving,the more kinetic
energy it has.
TYPES OF ENERGY
As this roller coaster car moves to
the top of the hill,it gains
potential energy.As it falls,its
kinetic energy increases and its
potential energy decreases.
An airplane flying through the air
has more kinetic energy than a
person riding a bicycle.
What are some Forms of Energy?
• Mechanical Energy is the combination of all the
potential and kinetic energy that something has.
• The energy we use everyday to physically move
When a person bikes through a mountain/hill,
it possesses a mechanical energy.When going
up and down to the top of a mountain/hill,it is
kinetic.When on the top,it is potential energy.
• Solar Energy comes from the sun.The word solar
means “comes from the sun”.People use solar cells
that change light energy from the sun into electricity.
o Solar calculators
o Solar panels to heat swimming pools
o Solar panels that provide light and power appliances in
homes or other buildings
Without solar energy,Earth would be just a ball of frozen rock with no
life.The sun is the source of almost all energy on Earth.Light from the
sun helps plants make food and oxygen.Its energy is stored in fossil
fuels that come from long-dead plants and animals.The sun’s energy is
also the source of weather.
• Light energy is the energy that is inherent from light.
It can also be viewed as a means by which
electromagnetic radiation is perceived from the
natural light sources e.g. the sun to living things.
This energy is carried in discrete packets called
photons i.e. In living plants for example, the light
energy is what splits organic molecules to make
chemical energy in a process called photosynthesis.
• A form of energy that is transferred by a difference in
temperature.Heat energy is the energy stored within atoms,
that can be produced when the organism vibrates and causes
A hot object is one whose atoms and molecules
are excited and show rapid movement. A cooler
object's molecules and atoms will be less excited
and show less movement.
• Electrical energy is the energy carried by moving
electrons in an electric conductor. It cannot be seen,
but it is one of our most useful forms of energy
because it is relatively easy to transmit and use.
• Sound is energy in the form of vibrations that travel
through matter.When a vibration reaches a particle
of matter,that particle starts to vibrate,too.In this
way,sound vibrations can spread out,not just in a
straight line,but in all directions.
• “Energy stored fuel.”
• It can be release by a chemical reaction,such as
burning or digestion.It is needed to change its
potential into kinetic energy.
Our muscles get energy from the food we eat.The
potential energy stored in food is chemical energy.
When it’s released,it gives us kinetic energy to move.
• Nuclear energy originates from the splitting of
uranium atoms in a process called fission. At the
power plant, the fission process is used to generate
heat for producing steam, which is used by a turbine
to generate electricity.
• A change from one form of energy to another is
called energy transformation.
• Law of Conservation of Energy states that energy can
change form, but it cannot be created or destroyed.
Therefore, the total amount of energy stays the same.
• In energy transformations, some energy is always lost to
the environment as thermal energy.
A television changes electrical energy into sound and light energy.
A toaster changes electrical energy into thermal energy and light.
A car changes chemical energy from fuel into thermal energy and
A flashlight changes chemical energy from batteries into light energy.
When you speak into your telephone, sound energy from your voice is
changed into electrical energy. The electrical energy is then converted
back into sound energy on another phone, allowing someone to hear you.
Light energy is converted into electrical energy using solar panels.
Campfires convert chemical energy stored in wood into thermal
energy, which is useful for cooking food and staying warm.
Nuclear energy generates a tremendous amount of thermal energy,
which can be converted into electrical energy in a nuclear power
• CONDUCTION- is the heating of an object from direct
contact between a heat source and the object.
EXAMPLE: A pan getting hot from the stove.
• CONVECTION- is heating of an object through the
movement of a fluid (a gas or liquid).EXAMPLE: The thermal
currents in the ocean or in the atmosphere.
• Radiation-is the heating of an object by radiant
energy traveling through space by electromagnetic
waves. EXAMPLE:The thermal energy coming to the Earth from the Sun
through infrared waves.