Post on 07-Oct-2014
transcript
http://phy.si
We have looked at simple energy flow diagrams. In each of the following examples, only the
useful output energy has been included:
However, a process cannot be perfectly efficient.
There is always some energy wasted, which is
normally given off as thermal energy or sound
energy.
Sankey Diagrams
SankeyDiagrams
We have looked at simple energy flow diagrams. In each of the following examples, only the
useful output energy has been included:
However, a process cannot be perfectly efficient.
There is always some energy wasted, which is
normally given off as thermal energy or sound
These can be used to show not
only what type of
transformation
also exactly how much energy
is given off.
This is the Sankey
a filament light bulb
electrical energy is put in, and
only 10J of useful light energy
is given out. Most of the
energy (90J) is wasted as
thermal energy.
GCSEP2
We have looked at simple energy flow diagrams. In each of the following examples, only the
These can be used to show not
what type of energy
transformation is going on, but
so exactly how much energy
Sankey diagram for
filament light bulb. 100J of
electrical energy is put in, and
only 10J of useful light energy
is given out. Most of the
energy (90J) is wasted as
thermal energy.
Energycannotbecreated
ordestroyed;onlychanged
fromoneformtoanother.
http://phy.si
Sankey Diagrams on Graph Paper
Sankey diagrams are usually represented on graph paper, as we can measure the size of the
arrow more accurately. The width of the arrow represents the amount of energy
We could also have worked this out as the total input energy minus the useful output
energy: 200J � 50J � 150J.
One square on this Sankey
diagram represents 5J of
energy. How much…
(a) … electrical energy is input?
(b) … useful sound energy is given off?
(c) …thermal energy is wasted?
SankeyDiagrams
on Graph Paper
Sankey diagrams are usually represented on graph paper, as we can measure the size of the
width of the arrow represents the amount of energy
In this Sankey
much energy has been wasted?
Input, 200J =
Useful, 50J =
� 1 little square =
� Waste, 15 squares =
We could also have worked this out as the total input energy minus the useful output
One square on this Sankey
diagram represents 5J of
How much…
energy is input?
(b) … useful sound energy is given off?
(c) …thermal energy is wasted?
GCSEP2
Sankey diagrams are usually represented on graph paper, as we can measure the size of the
width of the arrow represents the amount of energy.
In this Sankey diagram, how
much energy has been wasted?
little squares
little squares
1 little square = J
Waste, 15 squares = J
We could also have worked this out as the total input energy minus the useful output