Dr. Gambari, A. Isiaka
MEANING AND NATURE OF TECHNOLOGY
A Lecture Presented at University of Ilorin for Undergraduate
Students of Educational Technology Department.
11st November, 2013
Meaning of Energy
Different kinds of energy
Classification of Energy
How Energy can be changed from one form to into
First and second laws of thermodynamics that
summarise what happens during energy changes.
Examine some of the ways that energy is harnessed in
the modern world
Explain heat exchangers, heat pumps and air
conditioners, the internal combustion engine (the
engine in a car or truck), the electric motor and the
power stations that generate electricity for our homes
and factories. Sources of energy
WHAT IS ENERGY?
energy as the
capacity to do ‘work’.
In science, work refers
to almost anything that
can be done!
The children are using
their energy to dance.
the musician is using
her energy to sing
and play the base.
The energy of the
waterfall makes the
water move fast,
the energy of the
train enables it to pull
a heavy load at high
Anything that gets
moving, or makes
noise or heat or light
or electricity, is using
energy and doing
The energy is not the
same thing as the
work that is done;
energy is simply the
ability or readiness to
DIFFERENT KINDS OF ENERGY
mechanical energy (that is the energy
associated with the mass of an object),
chemical energy, and
Forms of energy that
involve motion are
classified as kinetic
forms of energy that
do not involve
motion are classified
as potential energy.
Kinetic energy is the energy
of moving things.
‘Kinetic’ comes from the
Greek word ‘kinesis’ meaning
The term kinetic energy is
used mainly for the
mechanical energy of a
However electricity, sound, Flywheel at a pumping station
light and heat all involve
motion, so they are often
regarded as forms of kinetic
energy is the energy
of anything that
moves and has
Kinetic energy is
associated with all
kinds of motion,
Electrical energy is a
stream of electrons
flowing through a
Electricity is a
convenient form of
energy because it
can be delivered to
homes and factories
through wires, and it
can easily be
converted into other
Sound energy is a pulse of
vibrations travelling through the air,
The source of the sound vibrates
and nudges the molecules in the
air surrounding it.
You can easily feel the vibrations
from a loudspeaker like the one
shown on the right.
A pulse of backwards-andforwards vibrations of the air
molecules carries the sound
energy through the air at a speed
of about 330 metres per second.
Light energy is an example of
includes radio and TV waves,
heat (infra-red) rays, light, X-rays
and γ-rays. These rays all carry
energy, but unlike sound waves
(which must be carried by a
medium such as air or water),
they require no medium. They
travel through space at a speed
of 3 x 109 metres per second.
light which provides energy for
life on Earth through
Heat energy is part of the
radiation that we receive
from the sun. We also get
heat energy from burning
fuels and in other ways.
Heat is a low grade form of energy because a lot of it is
always wasted as internal kinetic energy and therefore
cannot do useful work.
Potential energy is stored energy, or energy-in-waiting.
‘Potential’ comes from the Latin word ‘potentia’ meaning
power or capability.
The term potential energy is used mainly for the stored
mechanical energy of a stationary object which is being
acted on by a force. However, chemical and nuclear
energy are also forms of stored energy.
Mechanical potential energy
is the stored energy of a
stationary object that is being
acted on by a force; an object
that is poised, ready to move.
A large rock is balanced high
up on a cliff. It is being pulled
down by the force of gravity
but is supported by the rocks
underneath it. If this rock slips,
or if someone pushes it, it will
crash down and damage
anything that it hits.
Any object above ground
level has potential energy
of this sort.
The arrow is being pushed
forward by the tension in
the bowstring. When the
archer lets go of the
bowstring, it will shoot the
arrow through the air
towards its target.
Any stationary object that
is being pushed or pulled
by a piece of elastic, or a
spring, has potential
energy of this sort.
Chemical energy is the
potential energy that is
stored in substances that
are ready to undergo
A good example is an
electric cell or battery.
When the terminals are
connected and the circuit
is switched on, chemical
reactions in the cell will
send a stream of
electrons through the
circuit to do their work.
Other examples of chemical potential energy are
explosives and fuels, including food which is the fuel
for our bodies.
Nuclear energy is the potential energy that is stored in
the nuclei of atoms.
This energy is released slowly during radio-active decay
and fast during nuclear fission and nuclear fusion.
Nuclear fission is the source of energy in nuclear power
stations and atom bombs, and nuclear fusion is the
source of energy of the stars including our sun.
CHANGING ONE KIND OF
ENERGY INTO ANOTHER
Explosions: The head of a match contains
stored chemical energy. When we strike the
match, the match head explodes (gently) and
its chemical energy changes into heat and
light energy. chemical energy > heat (and
Industrial explosives such as dynamite contain
a large amount of stored chemical energy.
When dynamite is used to break rocks in a
quarry or a mine, the chemical energy
changes into kinetic energy as the rocks fly
apart; the explosion makes a lot of heat and
sound energy too! chemical energy > kinetic
energy (plus heat and sound energy)
Using a cell or battery: An electric
cell or battery contains stored
When a cell is connected to a light
bulb, the stored chemical energy
changes into electrical energy in the
wires, and the electrical energy in
the wires changes into light energy
(and a bit of heat) in the bulb.
chemical energy > electrical energy
> light (and heat) energy
the chemical energy stored in the
battery changes to electrical energy in
the wires that lead to the small electric
motor. The motor changes the
electrical energy into mechanical
kinetic energy in the form of a turning
pulley wheel that drives a larger pulley
wheel. The larger pulley wheel is
attached to an axel and, as the axel
turns, it winds up a string and lifts a
mass. Lifting the mass changes kinetic
energy from the motor into potential
energy in the raised mass.
chemical energy > electrical energy >
kinetic energy > potential energy
Using a dynamo: Many kinds
of electric motor can
convert energy in both
directions. If an electric
current flows through a
motor of this kind, the axel of
the motor turns; but
if, alternatively, something
makes the axel turn, then it
produces an electric current!
A motor that is used
backwards like this, to make
electricity, is called a
chemical energy (in the
fuel) > heat energy (from
the burning fuel) >
kinetic energy (in the
steam engine) >
electrical energy (in the
dynamo) > light energy
(in the light bulb).
potential energy (in
the water because it
is raised above the
ground) > kinetic
energy (in the
flowing water which
turns the paddle
wheel) > electrical
energy (in the
dynamo and the
wires) > light energy
(in the light bulb).
potential energy (in
the coiled spring) >
kinetic energy (as
the spring uncurls
and turns the pulley
wheels) > electrical
energy (in the
dynamo) > light
energy (in the light
Using food: The
energy that keeps us
warm and keeps us
moving, comes from
the chemical energy
stored in our food.
As they ride up the
hill, they change the
stored in their food
into kinetic energy in
their legs and in the
As they ride up the hill, they change the
chemical energy stored in their food
into kinetic energy in their legs and in
the moving bicycles. As they climb
higher and higher, some of this kinetic
energy is gradually stored as potential
energy. When they reach the top, they
no longer need to use energy from their
food to push the pedals around.
The potential energy due to their
height, gives them with all the energy
they need to freewheel back to the
bottom of the hill without pedalling! As
they speed downhill, their potential
energy is converted back into kinetic
The making of food and fuels
Plants are the producers at
the start of all food chains. In
the process called
they use light energy from the
sun to make carbohydrates
from carbon dioxide (in the
air) and water (in the soil).
After that, some of the
carbohydrates are converted
into lipids and proteins. In the
end, all our food and all our
fossil fuels come from plants.
light energy (from
sun) > chemical
energy (stored in
food) > kinetic
energy (legs moving
and bicycle moving
uphill) > potential
energy (stored as
height) > kinetic
woman firing a gun, and the cartridge that was
loaded into the gun
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