P2 - Collecting energy from the sun, Generating Electricity, Fuels for power Flashcards
What does the sun emit and transfer energy to the Earth as?
Light and heat
What can energy from the sun be captured and used to produce?
Electricity and heat
Why is energy from the sun known as renewable energy?
Because it won’t run out
What do photocells do?
Capture light energy from the sun on flat silicon surfaces
What are photocells made from?
Silicon
How do photocells work?
The suns energy is absorbed by the photocell, causing electrons to be knocked loose from the silicon atoms in the crystal. These electrons flow freely within the silicon; this flow of charge is called an electric current.
What is DC (Direct Current)?
An electric current, which travels in the same direction all the time.
Which three things does the power output of a photocell depend on?
The surface area exposed to the sunlight, the intensity of the light, and the distance between the light source and the photocell
What is a solar panel?
Lots of photocells joined together
Name three disadvantages of photocells
No power at night, no power during bad weather
Name three advantages of photocells
Renewable energy from the sun, no need for fuel as the sun as the energy source, no pollution or waste is produced, little maintenance is required once installed, they have a long life, and can operate in remote locations to give access to electricity without installing power cables.
How can power output be maximized by an efficient solar collector? What is a disadvantage of this?
The solar collector needs to track (follow) the position of the sun through the sky. This requires additional technology, so the set-up cost increases
What are convection currents?
Wind, caused by the Sun’s energy
What energy does a wind turbine transform into electrical energy?
Kinetic energy
Name three advantages of wind turbines
Wind is a renewable energy source, there is no chemical pollution or waste, and it’s free after set up costs
Name three disadvantages of wind turbines
Turbines require a large amount of space to deliver a reasonable amount of electricity, they’re dependent on the wind so are unreliable, and cause visual pollution
What is the dynamo effect?
When electricity can be generated by moving a wire/coil of wire near a magnet, or moving a magnet near a wire/coil of wire.
How does the dynamo effect happen?
The wire cuts through the lines of force of the magnetic field and a current is produced by electromagnetic induction in the wire (as long as it’s part of a complete circuit)
What happens within a generator to produce electricity?
A coil of wire is rotated in a magnetic field
What happens within a generator to produce electricity?
A coil
What does AC stand for?
Alternating current
In a generator, what type of current is produced and why?
Alternating current, because every half turn of the coil, it changes direction.
What are the four stages of producing electricity in power stations?
1) The fuel is burned to release heat energy
2) The heat boils water to produce steam
3) The steam drives the turbines, which drive generators
4) The generators produce electricity
What is the network of power that distributes the electricity produced by power stations around the country?
The National Grid
Why is a significant amount of the energy produced by power stations wasted?
Because at each stage in the electricity transfer process, energy is transferred to the surroundings in a non useful form, usually heat
What are the three fuels most commonly used in power stations?
Nuclear fuel, Biomass, and Fossil fuels
Give two examples of fossil fuels
Crude oil, coal, natural gas
Give two examples of biomass
Wood, Straw, Manure
Give an example of nuclear fuel
Uranium
Why does electricity have to be transmitted by the National Grid at a high voltage to reduce heat loss and costs?
Because as an electric current is transmitted along a wire, it heats up due to collisions within the material. The wire loses this heat to the environment. If the electricity is transmitted at a higher voltage, but the power remains the same, the current in the wire is reduced. A lower current means less heating of the wires, so less energy is lost from the wires as heat.
Why does electricity have to be transmitted by the National Grid at a high volatge to reduce heat loss and costs?
Because as an electric current is transmitted along a wire, it heats up due to collisions within the material. The wire loses this heat to the environment. If the electricity is transmitted at a higher voltage
What are transformers used for?
Increasing and decreasing the voltage before and after transmission.
Why are transformers used?
Because the voltage after transmission is too high for the consumers, so they are used to reduce the voltage for safe use.
What are transformers that reduce voltage called?
Step-down transformers
To encourage consumers to use electricity at night, what do electricity companies do?
They offer an off-peak rate for seven hours every night.
What are the advantages and disadvantages of Economy-7?
It’s less expensive for the consumer, it avoids wasting electricity, and there is less demand for electricity at night, but it is inconvenient to run appliances at night because of the noise they make
What is an electric current?
The flow of electrical charge from the power supply to the components in the circuit
What is an electric current?
The flow of electrical charge
What is a watt?
1 watt is the transfer of 1 joule of energy in one second
What is a kWh (Kilowatt hour)?
A measure of how much electricity has been used in an hour
What is a kWh (Kilowatt hour)?
A
What does the number of kWh units of electricity used by an appliance depend on?
The power rating of the appliance, and the time that the appliance is left on for.
