Unit 3 - Lesson 10: Energy Efficiency & Sankey Diagrams

Question 1

Is energy a scalar or a vector?

Answer 1

A scalar.

Question 2

What are scalars?

Answer 2

Scalars are quantities with a magnitude (size) only.

Question 3

Some energy is always wasted in appliances. True or false?

Answer 3

True.

Question 4

What kind of diagram can show how much energy is wasted?

Answer 4

Sankey diagram.

Question 5

Draw a Sankey diagram.

Answer 5

https://i.pinimg.com/736x/93/b6/d8/93b6d85e7c36379c35d4e7853730bdde.jpg

Question 6

The energy efficiency of an appliance is given as a percentage. You can calculate energy efficiency using what formula?

Answer 6

Efficiency = Useful energy output/Total energy output x 100%

Question 7

What is the total energy input the same as?

Answer 7

The total energy output.

Question 8

If a question tells you the useful energy output, what value do you subtract this from?

Answer 8

You’ll need to subtract the useful energy output from the total output.

Question 9

If a question tells you the wasted energy output, what value do you subtract this from?

Answer 9

You’ll need to subtract the wasted energy output from the total output.

Question 10

Always divide the (smaller/larger) number by the (smaller/larger).

Answer 10

Always divide the SMALLER number by the LARGER.

Question 11

Rearrange (Efficiency = Useful Energy Output/Total Energy Output x 100%) to find useful energy output.

Answer 11

Multiply both sides by total energy output:
1. Efficiency x Total Energy Output = (Useful Energy Output/Total Energy Output x Total Energy Output) x 100%
2. Efficiency x Total Energy Output = Useful Energy Output x 100%
Then divide both sides by 100. This gives:
3. Useful Energy Output = Efficiency x Total Energy Output/100

Question 12

Rearrange (Efficiency = Useful Energy Output/Total Energy Output x 100%) to find total energy output.

Answer 12

Multiply both sides by total energy output:
1. Efficiency x Total Energy Output = Useful Energy Output x 100%
Then, divide both sides by efficiency. This gives:
2. Total Energy Output = Useful Energy Output x 100/Efficiency