# Worksheet: Sankey Diagrams

In this worksheet, we will practice correctly drawing and interpreting Sankey diagrams for processes that involve the transfer of energy.

**Q3: **

The image shows a Sankey diagram of a 100 W light bulb.

What does 1 square of the diagram represent?

How much energy is wasted as heat by the light bulb?

What is the efficiency of the light bulb?

- A70%
- B10%
- C20%
- D30%
- E50%

**Q4: **

The image shows a Sankey diagram for a 1.7 kW kettle turned on for 3 minutes.

Is the majority of the energy supplied to the kettle wasted or transferred usefully?

- AThe majority of the energy is transferred usefully.
- BThe majority of the energy is wasted.

What is the efficiency of the kettle?

- A90%
- B50%
- C100%
- D10%
- E0%

**Q5: **

The image shows a Sankey diagram for a light bulb that has been drawn incorrectly. In which of the following ways has the diagram been drawn incorrectly?

- The value represented by one square of the diagram is not consistent.
- 1 square of a Sankey diagram should always represent 1 watt or 1 joule.
- Sankey diagrams can only be used for energy, not power.
- The two output arrows both represent 20 W, but they are of different widths.
- The total output power is not equal to the total input power.

- Aa, c, and e
- Ba, b, and e
- Cd, b, and c
- Da, d, and e
- Ee, b, and c

**Q6: **

Diagram (a) is a Sankey diagram of a 1.8 kW kettle. Diagram (b) is a Sankey diagram of an 80 W light bulb.

Which device is more efficient?

- AThe kettle
- BThe light bulb

What is the efficiency of the kettle?

- A
- B
- C
- D
- E

What is the efficiency of the light bulb?

- A
- B
- C
- D
- E

**Q7: **

The image shows Sankey diagrams for four different processes.

Which process is the most efficient?

- A(b)
- B(a)
- C(c)
- D(d)

Which process is the least efficient?

- A(d)
- B(c)
- C(b)
- D(a)