2 - Energy

Question 1

What is efficiency?

Answer 1

• A measure of how good a device is at changing energy from one store to another

Question 2

How can efficiency be increased?

Answer 2

By reducing the amount of unwanted energy transfers that are produced

Question 3

What is energy?

Answer 3

• Often defined as ‘The capacity to do work’
• Measured in Joules (J)

Question 4

What are the main energy sources available for use on Earth?

Answer 4

• Fossil Fuels
• Nuclear Fuel
• Bio-Fuel
• Wind
• Hydroelectricity
• Tides
• Sun
• Geothermal
• Water Waves

Question 5

How are both renewable and non-renewable energy sources used?

Answer 5

Non:
- Power stations that use fossil fuels or nuclear fuel are very reliable sources of energy
- They operate almost continuously
- When additional power is needed, gas power stations are usually used because they will start up very quickly
Renewable:
- Water power eg tidal and hydroelectricity are reliable and predictable
- These two types can also be used to supply additional demand
- Many of the renewable sources are unreliable, including wind and solar energy

Question 6

What are the patterns and trends in the use of energy resources?

Answer 6

• Demand for energy varies with the time of year and the time of day
• During evenings a lot of energy is needed for heating, lighting and cooking
• Very little needed overnight
• During winter there is more heating and lighting used than in summer

Question 7

What is meant by the conservation of energy?

Answer 7

• Energy can be transferred usefully, stored or dissipated, but it cannot be created or destroyed

Question 8

What is an energy source?

Answer 8

• An energy source is something we can release energy from , eg a fuel
• Used in power stations to generate electricity
• Energy source itself is a primary source
• Electricity produced is a secondary source

Question 9

What are some ways of reducing unwanted energy transfers?

Answer 9

Friction:
- Adding bearings to prevent components directly rubbing together
- Lubricating parts
Heat:
- Using lower resistance parts/lowering the current; reduces amount of heat produced
- Thermal insulation

Question 10

What are the energy stores? Where are they stored (~)?

Answer 10

• Gravitational Potential Energy (GPE) ~ Mass due to position
• Kinetic Energy (KE) ~ Moving objects
• Thermal Energy ~ Mass due to temp
• Chemical Energy ~ In chemicals
• Elastic Potential ~ Compressed/stretched items
• Electrostatic ~ When elec charges interact
• Magnetic ~ When two magnetic objects interact
• Nuclear ~ Atomic Nuclei

Question 11

How is energy transferred from one store to another?

Answer 11

Radiation - Electromagnetic waves & sound
Electrically - Electrical current
Mechanically - Force pushing/pulling
Heating - Temp difference between one point & another