Conservation And Dissipation Of Energy

Question 1

What is the key rule about energy?

Answer 1

Energy can’t be created or destroyed but can be stored or dissipated
When there are energy transfers in a closed system there is no net change in the total energy

Question 2

When is energy dissipated?

Answer 2

In all system changes energy is dissipated
It is then stored in less useful ways
Often described as wasted eg light bulb producing heat as well as light

Question 3

How do we reduce wasted energy?

Answer 3

1. Good insulation eg Building thermal insulation: achieved by:
   Materials over low conductivity in the walls
   Using thicker walls

Good heat conductors are said to have high thermal conductivity

Question 4

How do you calculate energy efficiency?

Answer 4

Efficiency = useful output energy/total input energy transferred
Efficiency = useful power output/total power input
Closer to 1 (100%) = more useful energy the device is transferring

Question 5

How can you improve efficiency? Give an example

Answer 5

Oil a bike chain
Lubricate or sharpen a drill bit
The condenser boiler uses water vapour to preheat incoming water