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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