P2 1-8

Question 1

What are the benefits of using solar cells?

Answer 1

• do not need much maintenance and no need for a fuel.
• long life and do not produce any waste.
• renewable energy resource.
• no need for power cables and so they can be used in remote locations

Question 2

Disadvantages of photocells?

Answer 2

• you would need a very large area of photocells to generate the amount of electricity that is used by a small town.
• Photocells only work when the Sun is shining, and not at night or in bad weather.

Question 3

How does a photocell transform light into electrical energy?

Answer 3

When light shines on a photocell, energy is absorbed by silicon atoms in the photocell. Electrons are knocked out of the silicon atoms. These electrons are then free to flow, creating the direct current.

Question 4

What does the amount of current produced from photocells depend on?

Answer 4

• intensity of the light shining on it
• how far the solar cell is from the light source
• the area of solar cell that has light shining on it

Question 5

How does passive solar heating work?

Answer 5

• light energy from sun passes though the glass
• light energy absorbed by surfaces which heats them up
• surfaces emit longer wavelength infrared radiation
• longer wavelength radiation reflected by glass

Question 6

How does a solar stove work?

Answer 6

Light energy from a larger area is reflected by curved mirrors on to a cooking pot.

Question 7

How do wind turbines work? Advantages and disadvantages?

Answer 7

The kinetic energy of the wind can be used to drive wind turbines directly.

Pros:
- Wind turbines are a renewable energy resource.
- They do not produce any waste
Cons:
- many people think that they spoil the landscape.
- The wind speed has to be high enough.
- They must also be built where they are not sheltered from the wind.
- take up a large area.

Question 8

What is the Dynamo effect?

Answer 8

One way to generate electricity is to move a piece of wire between the poles of a magnet. This creates a voltage. An electric current then passes through the wire, giving a reading on a ammeter.

Question 9

What makes the size of the current increase in the Dynamo effect?

Answer 9

• stronger magnets are used
• there are more turns of wire (making a coil)
• you move the wire faster.

Question 10

What is a generator? How does it work?

Answer 10

To induce a voltage, the coil of wire rotates inside a magnetic field instead of moving through it.

Question 11

What is a thermal power station?

Answer 11

An energy source that can be fossil fuels, nuclear or biomass to heat water.

Question 12

How is power wasted in a power station?

Answer 12

A significant amount of heat energy is transferred to the environment and is wasted.

Question 13

What is the greenhouse gas effect?

Answer 13

Most electromagnetic waves are able to pass through the atmosphere. However, some wavelengths are absorbed. Some gases within our atmosphere absorb infrared radiation and prevent this heat from radiating into space.

Question 14

What are greenhouse gasses? Examples?

Answer 14

Gases that absorb infrared radiation such as water vapour, methane and carbon dioxide

Question 15

What are the sources for greenhouse gases?

Answer 15

Water vapour
Natural source - the water cycle

Methane
Natural source - animal waste
Man made source - intensive farming + burning fossil fuels

Carbon dioxide
Natural source - volcanoes + waste from organisms
Man made source - burning fossil fuels + transport

Question 16

What are the three steps in the greenhouse gas effect?

Answer 16

1 - shorter wavelength electromagnetic waves from sun pass through atmosphere

2 - radiation absorbed by Earth - warms it. Earth then emits longer wavelength infrared radiation

3 - gasses in our atmosphere absorb this which heats it up

Question 17

What is the largest gas in the greenhouse effect?

Answer 17

Water vapour - 50%

Question 18

What happens at a step up transformer, step down transformer ?

Answer 18

• electricity goes from power station to a step-up transformer where the voltage is increased.
• electricity goes through a step-down transformer to reduce the voltage to a safer level for use by consumers.

Question 19

Why does the national grid use high voltage transmission?

Answer 19

• When a current flows through a wire, there is a heating effect and this dissipates some energy.
• The larger the current, the more heat is produced, and the more energy is wasted.
• if you increase the voltage, the current decreases.
• This reduces the amount of energy wasted in the power lines.

Question 20

Advantages and disadvantages of power lines being underground?

Answer 20

Pros:
- it reduces their visual impact
- reduces the risk of tall objects colliding with them.
Cons:
- it is expensive
- have to be insulated and waterproofed.
- if something goes wrong, the ground has to be dug up.

Question 21

What is a turbine? How does it work?

Answer 21

In every fossil fuel power station, fuel is burnt and the heat produced turns water to steam. This steam turns a turbine. The turbine spins a generator to produce electricity.

Question 22

Advantages and disadvantages of fossil fuels?

Answer 22

Cons :

• releases a number of pollutants into the atmosphere such as carbon dioxide, which contributes to global warming.
• All three fossil fuels (coal, crude oil, and gas) have to be mined and transported, which can have negative impacts on the environment.

Pros:
- Fossil fuel power plants are an established, reliable technology, producing large amounts of electricity.

Question 23

Examples of biofuels ?

Answer 23

a Wood, woodchips, and straw from specially grown trees or
crops
• Alcohol fuels (such as ethanol), produced by fermenting
sugar cane crops.
• Methane gas, given off by animal waste (manure) in
storage tanks called sludge digesters, and also from other rotting waste (for example food waste from homes).

Question 24

Advantages and disadvantages of biofuels?

Answer 24

Pros:
- Uses products which might otherwise be wasted, so the fuel costs are very low.
- Power stations can also supply hot water to local industry/houses.
- burning biomass releases carbon dioxide into the atmosphere. However there is no overall increase in carbon dioxide as the amount released is the same as the plant absorbed.

Cons :
- Releases atmospheric pollutants.
- In developing countries, land which could be used for food is now used to grow crops for biofuels, leading to food shortages.
- Power plants can be ugly to look at (visual pollution).

Question 25

What happens inside a nuclear reactor?

Answer 25

atoms of uranium or plutonium undergo nuclear fission. This releases a great amount of energy in the form of heat. The heat is used to turn water to steam, as in other thermal power plants. The steam drives turbines. No burning is involved, so there is no release
of carbon dioxide.
The uranium fuel used in most reactors is a non-renewable resource. We have enough to last thousands of years, but we will eventually run out of it.

Question 26

What do you do with radioactive waste?

Answer 26

The radiation from this waste decreases over time, but the waste remains dangerous for millions of years. To store it safely it is usually encased in glass and buried deep underground, away from any water sources.Radioactive waste can be reprocessed. Unused uranium can be extracted and put back into reactors.

Question 27

What are the benefits of nuclear power?

Answer 27

• Large amounts of electricity can be generated for each kilogram of fuel used.
• The fuel is readily available and, unlike fossil fuels, it won’t run out for thousands of years.
• No polluting gases such as carbon dioxide are produced, so there is no contribution to global warming or acid rain.

Question 28

Disadvantages of nuclear power?

Answer 28

• The cost of building the plant and taking it down when it has finished can be quite high.
• Nuclear fuel has to be processed before it can be used.
• Nuclear reactors have a very slow start up time. It
takes a long time to increase or decrease the amount of electricity they are generating.
• It can be very expensive to process radioactive waste, and the stored waste may be a future terrorist target.
• There is always the risk of an accident that could
release radioactive waste into the environment.