UNIT 13. ENERGY
ENERGY
·
What
is energy?
Energy is the capacity to produce changes. These changes can be produced
by heat, light, electricity, etc. Energy is always changing from one to
another.
SOME FORMS OF ENERGY
-
Heat
energy
-
Electrical
energy
-
Kinetic
energy
-
Light
energy
-
Chemical
energy
LIGHT ENERGY
·
Light
and light sources
A light source is anything which emits light.
·
The
properties of light
-
It
moves in a straight line.
-
It
moves in all directions.
-
It
travels very fast.
-
It
interacts with the objects it reaches.
SOME PHENOMENA OF LIGHT
-
Shadow:
it is a dark area produced because light can´t pass through an opaque object.
-
Reflection:
when light can´t pass through an object it bounces off the object.
-
The
composition of light: it is a mixture of different colours (red, orange,
ywlloe, green, blue, indigo and violet.
ENERGY SOURCES
·
What
are energy sources?
An energy source is an object from which we obtain energy. Enery sources
can be:
-
Renewable:
they do not finish with the use. An example is wind energy. Wind turbines
produce electricity and they do not pollute. Other example is solar energy.
Solar panels produce heat and electricity and they do not pollute.
-
Non-renewable:
they can finish. For example, coal, which is excavated in mines and it
pollutes. Other example is oil, which is extracted from oil Wells. Petrol is
made from oil. It causes pollution.
THE
EFFICIENT USE OF ENERGY
·
We
need energy
We use a lot of non-renewable sources of energy and it damages the
environment. We must use energy more efficiently:
-
We
must use less non-renewable energy because it pollutes and can run out.
-
We
must use more renewable energy because it does not pollute and it can not run
out.
-
We
must save energy: using more efficient motors, recycling and reusing materials,
etc.
