Download Energy_Forms_and_Efficiency

Is there an Ultimate
Energy Source?
Is there an ultimate energy
source?
The Sun
is the
ultimate
energy
source
The grass gets its energy
from the Sun via
photosynthesis.
The lamb gets its energy
by eating the grass ….
…. and WE get our
energy by eating
the lamb!
Forms of Energy
Gravitational Potential Energy
This is energy when
something is ‘out of position’.
This rock climber has
potential energy. The further
she climbs – the more
potential energy she would
gain.
Water held behind a
dam has this type of
energy too.
Chemical Potential Energy
When a fuel burns, its
energy is released by
chemical reactions. The
energy stored in the fuel
is called chemical
potential energy (or
chemical energy for
short). Batteries also
store chemical potential
energy.
Kinetic Energy
This is energy
due to motion.
All moving
objects have
kinetic energy
The faster they
move (or the more
mass they have)
the more kinetic
energy they have
Elastic Potential Energy
A stretched rubber band can
do work when released. It has
elastic potential energy
Electrical Energy
In circuits, the current
is a flow of tiny charged
particles called
electrons. Electrons can
transfer energy, for
example from a circuit
to a hairdryer. They
have electrical energy.
Nuclear Energy
An atom has a nucleus
at its centre. This is
made up of particles,
held by strong forces.
In some atoms the
particles become
rearranged or the
nucleus splits and
energy is released.
Thermal Energy
When hot objects cool
down, their atoms and
molecules slow down and
lose energy. This is
known as thermal
energy or heat.
Radiated Energy
Examples of this
are light from a
lamp and radio
signals from a
transmitter.
Sound
Anything that makes a
noise has this form of
energy. For example air
compressions from a
loudspeaker or other
sound source.
Energy Transfers
What is the energy conversion in each
of the solar cells?
Light (radiated)
Electrical Energy
What are the energy transfers
in this match?
Chemical Energy
Light & Heat
Sound is wasted
What energy conversions happen in a windmill?
Kinetic Energy
Electrical Energy
What is the unit for ENERGY?
The Unit for all forms of
energy is the Joule (J).
The unit is named after the
scientist in the picture.
1 kJ = 1,000J
1 MJ = 1,000,000J
Conservation of
Energy &
Efficiency
What is the Principle of
‘Conservation of Energy’?
ENERGY can never be
CREATED or DESTROYED –
it can only be CONVERTED
from one form to another.
Another important principle is:
Energy is ONLY USEFUL when it is
CONVERTED from one form to another.
‘Energy cannot be created or destroyed, but it
can be changed from one form to another’
Chemical Energy
Light (radiated) Energy wanted
Heat (thermal) Energy wasted
The wasted Heat Energy now heats up the surroundings. It is
NEVER destroyed!
Are energy conversions
100% efficient?
NO device is 100%
efficient and the
wasted energy is
dissipated usually as
HEAT & SOUND
Think of this washing machine.
It gets noisy and hot when it is
switched on to wash our clothes
What is EFFICIENCY?
The efficiency of any device is defined as:
Efficiency =
Useful energy OUTPUT
Useful energy INPUT
Energy
out
Efficiency x Energy In
Efficiency can be
expressed as a fraction,
decimal or percentage
Calculate the efficiency of this computer
1200J of electrical energy is
supplied to the computer.
200J of energy are wasted
in the form of heat & sound.
Efficiency = Energy output
Energy Input
= 1,000 / 1,200
= 0.83 (or 83%)