P8 Flashcards
What is the speed of sound?
330m/s
What are the three fossil fuels?
⚫️Coal
⛽️Gas
🛢Oil
(All very energy dense)
What are the disadvantages of fossil fuels?
They emit carbon dioxide (greenhouse gases)
They are bad for the environment
They are NON- renewable sources of energy
What is the difference between a renewable source of energy and a non -renewable
Renewable: won’t run out as it is not used up when releasing energy
Non- renewable: will run out as it is used up
What are some examples of renewable energy sources?
- Solar ( energy from sun light)
- Wind (energy from the wind movement)
- Geothermal (energy from the earth’s heat)
- water high up in dams (hydroelectricity)
- tidal
How do fossil fuel power plants work?
- Fossil fuel is burned
Through this chemical potential energy turns into kinetic energy - The kinetic energy from burning the coal heats up water into steam
- The steam turns the turbine because of pressure
- Turbine turns the generator on
- The generator makes electricity
What is the greenhouse effect?
The earth’s atmosphere traps the suns heats
What are some advantages of fossil fuel power plants?
Reliable
Cost effective
How do nuclear power plants work?
The same way as fossil fuels but instead of burning a fuel , the kinetic energy comes from nuclear fission reactions
What are some uses for energy sources?
What are the disadvantages of nuclear power plants?
The radioactive waste is difficult to dispose of
It’s quiet dangerous.
Non- Renewable
What are the advantages of nuclear power plants?
No green house gases
Lots of energy per kg that fossil fuels (efficient)
What is a biofuel?
A renewable fuel that is obtained from the recent living.
Eg: methane gas from sewage, ethanol, sugars,wood.
✅carbon neutral
How are biofuels carbon neutral?
Carbon dioxide is given out when a biofuel is burned however as the plants photosynthesise they take the carbon dioxide back in
Why is coal non-renewable but wood renewable?
Coal takes millions of years to form, so it will run out before any new coal is formed. However wood only takes a few years to grow and so we can regrow it at the rate of our usage.
what is the difference between an energy fuel and an energy source?
sources: use energy flows , energy harnessed from natural resources
fuels: stores energy and must be extracted
How does electricity get sent to your homes?
Power plant —step up transformer—cables/pylons—step down transformer—home (mains/sockets)
What is the national grid?
A series of cables and pylons that transfer electrical energy generated from the power plant to homes and businesses.
What is the process of transfer for the national grid?
1️⃣Power station
2️⃣step up transformer
3️⃣cables and pylons
4️⃣step down transformer
5️⃣underground mains cable
What does a step up transformer do?
It increases the p.d, this decreases the current (as the power stays the same)
P=I✖️V
This minimises heat loss
How does decreasing the current decrease heat loss?
Normally when an electron hits a metal ion , it’s energy is transferred to the surroundings as heat.
Deceasing the current means that there are less electrons in the wires, therefore less hit ions and less release heat.
What does a step down transformer do?
It decreases the p.d
P= I ✖️V
This increases the current
Allowing appliances at home to run without causing problems
What problems do high p.d cause?
🟡risk of electrocution and death
⚪️ appliances need to have low p.d otherwise won’t work
What is the transformer power equation?
P=I✖️V
Power of each side of the transformer should be the same (primary circuit and secondary circuit)
(I✖️V) = (I✖️V)
What is the efficiency of a transformer?
efficiency of a transformer= power out (secondary circuits)➗power in (primary circuit)
✖️100
What is the average voltage in UK’s mains?
230v- average
330v -highest
-330v - lowest
What is the domestic electricity supply in the UK?
230v a.c at 50Hz
Describe the generator effect
A wire carrying no current is spun (force) within a magnetic field. As the wire cuts the field lines, electrons are slammed the corners. Now we have a p.d , allowing current to flow
What is direct current?
Electric current only flows on one direction
- provided by batteries and cells
What is alternating current?
Current which continually reverses direction.
Normally have higher p.ds
Current is alternating because p.d is alternating
Describe a voltage time graph for DC supplies
A horizontal flat line at one voltage
Describe a voltage time graph for an AC supplies
Basically a sine graph , with the highest value being 330 and the lowest being -330. But the average is 230
Why is the average 230?
Because more time is spent in that range
How is a high of 330v achieved?
Highest rate of cutting field lines because the wire is exactly perpendicular to the field lines
What happens to devices when 0 is hit?
Because of clever engineering the device can carry on.
However in the olden times the lights would not flash when they reached zero . This is because the change is too fast to see but would cause headaches as it was going down slightly
What does a voltage time graph look like for AC with a diode?
The sin graph, but all negative graph cut off from the bottom
Describe the live wire:
A brown wire, where current comes into the appliance
Describe the neutral wire
A blue wire, where current comes out of the appliance
Describe the earth wire
A green and yellow wire, that takes away extra electrons from the wrong place and leads them to the ground.
Is what saves YOU
Describe the fuse
A tube , next to the live wire. If current is too high then it will heat up and melt - stopping the current, before exit enters the device
It saves the APPLIANCE, and reduces the risk of fires
What is the difference between 2 core wires and 3 core wires?
2 core wires do not have an earth wire, only a live and neutral. This is because they are double insulated. 230 is such a low p.d , it cannot get through plastic
3 contain the earth wire
What is the longest pin on the plug?
The earth wire. If it is plastic, this is probably used for stability rather than a wire
How do we know light is red shifted ?
Black lines correspond to the specific wavelengths of light absorbed by certain atoms in the star (since all stars contain hydrogen and helium. All spectra from stars contain a series of very specific black lines, which shift towards longer wavelengths implying light has undergone a Doppler shift.
What is the composition of the solar system?
What are the two overall forces adding upon a star/planet?
What is the life cycle of a star?
Graph of frequency and intensity of radiation at each frequency
Describe the Earth’s structure
A liquid outer core, able to do so because of pressure
How to p waves and S waves travel through the Earth?
Describe the forces acting upon a satellite
What are some dangers of live wires, even if the switch in mains circuit is open ?
The live wire may become loose inside an appliance, it can touch a metal casing. If someone touches the casing there will be a potential difference of 230v (0 you) and (230v live wire). A dangerous current could flow through you
