P8.2 Powering Earth

Question 1

What are the differences between renewable and non-renewable energy sources?

Answer 1

Renewable energy sources will not run out on a timescale of millions of years. Other sources are non-renewable because they take millions of years to form

Question 2

What are the renewable energy sources?

Answer 2

Biofuels
Sun
Tides
Wind
Geothermal
Gravity on Water

Question 3

How do we heat our houses?

Answer 3

Fossil Fuels
House Design
Solar Water Heating System
Cracking

Question 4

What are the ways in which we generate electricity?

Answer 4

Fossil fuels
Biofuels
Nuclear fuel
Solar power
Tidal power
Wind power
Geothermal power
Hydroelectric power

Question 5

Why has our use of different energy sources changed?

Answer 5

Population
Use of fuel consuming devices
Electricity generation

Question 6

What are the issues with fossil fuel usage?

Answer 6

Finite resource
Expensive extraction from finite reserves
Greenhouse effect
Climate change

Question 7

How do people decide which energy source to use?

Answer 7

Cost (to set up, use, extract)
Environmental Impact
Contribution to Climate Change
How long does it last

Question 8

What is the national grid?

Answer 8

Power stations, transformers, grid network and transformer substations are all part of the National Grid to supply electricity to your house

Question 9

How are transformers used in the National Grid?

Answer 9

Transformers change potential difference to reduce the heating effect making it more efficient. Step up transformers reduce heating effect whereas step down transformers make PD applicable to a home

Question 10

How does PD change through national grid?

Answer 10

25kV from power station
275kV over long distance grid network
132kV over short distance grid network
230V for homes

Question 11

Why is there less heating at high voltages?

Answer 11

Having a high voltage means there is a low current. Wires heat up because current is brought into it which transfer energy to the surroundings. The amount of heating depends on the current size and resistant of wires

Question 12

What is equation over transformers?

Answer 12

Vp * Ip = Vs * Is

Question 13

What is the mains?

Answer 13

This is domestic supply of 230V supplied to a home. Generators in power produce an alternating current which is transmitted to houses.

Question 14

What is the voltage produced by an appliance?

Answer 14

Direct Voltage

Question 15

What are the 2 wires in a plug that interact with your appliance?

Answer 15

The live wire (brown) and neutral wire (blue) make a complete circuit with the appliance.

Question 16

What does the 3rd wire in a plug do?

Answer 16

The earth wire connects the case to a metal pole buried underground so dangerous current flows through the earth wire and not people.

Question 17

How else can plugs be kept safe?

Answer 17

The case of the plug can be made of plastic so no current can flow and so these appliances are double insulated

Question 18

What is the formula for kWh?

Answer 18

Kilowatts per Hour = (Watts * Hour)/1000