Energy dissipation and Efficiency

Question 1

What is dissipation?

Answer 1

Dissipation is where energy is ‘wasted’ by being transferred out to the surroundings.

Question 2

What is an example of dissipation?

Answer 2

Friction transfers energy when a cyclist brakes by:
When the bike moves along all the energy is in the kinetic energy store when the brakes are applied it is mechanically transferred into thermal energy via friction. The breaks don’t stay hot so thermal energy can be dissipated which cools them down.

Question 3

Energy cannot be ___________ or ___________

Answer 3

Energy cannot be created or destroyed.

Question 4

Input energy= ______________+_______________

Answer 4

Input energy=Useful output energy + wasted output energy

Question 5

What is the equation to work out efficiency?

Answer 5

………………..Useful output
Efficiency= ———————– (X100 for a %)
……. Total Input

Question 6

What 2 forms can you use to represent efficiency?

Answer 6

Decimal and percentage

Question 7

What does efficiency mean?

Answer 7

Efficiency measures the proportion of energy which is useful.

Question 8

What graph is used to show the efficiency?

Answer 8

Sankey Diagram

Question 9

If the total amount of energy is 200J but only 60J are used what is the efficiency?

Answer 9

0.3 or 30%

Question 10

If the total amount of energy is 700J but 47J are wasted what is the efficiency? 1dp

Answer 10

0.9 or 93.3%

Question 11

How to reduce wasted energy from friction between moving parts causing heating?

Answer 11

Use oil to lubricate the moving parts to reduce friction (like WD-40)