Transcript File

In today’s modern, technological society the term “energy
conservation” is generally described as meaning
“conserving energy”,
in the sense that we aim to use less “energy” to do the
same amount of “work”
Examples Include:
•Improving insulation of
houses and other
buildings
•
Improvements in the efficiency of lighting and
other electrical devices
•Making cars which use fuel more efficiently
However in technology and science the
‘Conservation Of Energy’
has an older and different meaning.
It is looked upon as a rule.
The 1st law of “Thermodynamics” is also known as the:
“Conservation Of Energy”
The principle of the conservation of energy states that:
“energy can neither be created nor destroyed”
Therefore is can only be changed from one form to
another…
“Transformed’
Or
“Converted’
By this we mean that:
“For a closed system, where no energy goes in or out, the
total energy within the system must always be the same,
although its form may change”.
For example if we consider a pendulum:
The formula to calculate the potential energy is:
E(p) = m x g x h
The mass of the ball = 10kg
The height, h = 0.2m
The acceleration due to gravity, g = 9.8 m/s^2
Substitute the values into the formula and you get:
PE = 19.6J (J = Joules, unit of energy)
The position of the blue ball is where the Potential
Energy E(p) = 19.6J while the Kinetic Energy E(k) = 0.
As the blue ball is approaching the purple ball position the
E(p) is decreasing while the E(k) is increasing.
At exactly halfway between the blue and purple ball
position the E(p) = E(k)
The position of the purple ball is where the Kinetic
Energy is at its maximum while the Potential Energy
E(p) = 0.
At this point, theoretically, all the E(p) has transformed into
E(k)
Therefore now the E(k) = 19.6J while the E(p) = 0.
The position of the pink ball is where the Potential
Energy E(p) is once again at its maximum and the
Kinetic Energy E(k) = 0.
We can now say and understand that:
E(p) + E(k) =
E(p) =
0
- E(k)
The sum of E(p) and E(k) is the total mechanical energy:
Total Mechanical Energy = E(p) + E(k)
NB: This is with the absence of outside forces such as friction
Using our “common sense” we know that it's impossible for
the pendulum to swing higher than the height (h) without
giving it a push yourself (i.e. adding extra energy).
If there was no friction, the pendulum would swing back
and forth forever because of the law of conservation of
energy.
On the other hand, in an open system such as a power station, this rule
leads to the conclusion that the total energy input to the system must
be exactly equal to the total energy output.
The extent to which the output energy is able to do useful work  that
is, of the desired type  is called the efficiency of the system. We
calculate this by comparing the useful output from the system with its
energy input.
How energy can be converted or transformed is of prime
importance to the technologist.
Some forms of energy are directly interchangeable (for
example potential and kinetic) but others need to go
through several changes to arrive at the final desired form
(for example chemicalheatkineticelectrical.
A light bulb converts electrical energy into light energy.
ELECTRICAL
ENERGY
LIGHTBULB
LIGHT
ENERGY