Physics Module 2

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How do photocells create electricity?
Photocells are made of impure silicon which has lots of free electrons. When sunlight shines, photons are absorbed causing some of the electrons to be knocked loose which then travel around a circuit - this is electricity
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What are the advantages of using photocells?
They ahve no moving parts - they're sturdy, require low maintenance and last a long time / No power cables or fuel / Renewable energy source / Doesn't pollute enironment
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What are the disadvantages of using photocells?
They will not work unless there is sunlight - night or bad weather means limited energy produced
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What is a solar oven?
When the suns rays are reflected off a curved mirror and are concentrated in a small area to heat stuff up
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What is passive solar heating?
Where energy from the sun is used to heat something directly
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How does the sun lead to wind turbines?
The Sun heats up the air causing it to rise and forcing cool air to take its place. This causes a convection current and so wind to turn the turbines in wind turbines
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What are the advantages of wind turbines?
The wind is renewable energy / Cheap to run / No polluting waste
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What are the disadvantages of wind turbines?
1500 wind turbines replace one coal fire power station / They cause visual and noise pollution / Wind not always reliable / Impossible to increase supply when there's demand / Difficult to find places to build / Expensive to build
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How do power stations provide electricity?
Heat a fuel in the boiler to produce steam.The steam then turns a turbine which in turn turns a generator. The generator rotates a coil in a magnetic field which produces electricity
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What are the advantages of fossil fuels?
They are readily available / a concentrated source of energy
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What are the disadvantages of fossil fuels?
They cause pollution (e.g greenhouse effect - CO2 and acid rain) / Most of the fuel is bought from other countries so we don't have control of price or supply / They are running out (finite resource)
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What are the advantages and disadvantages of biomass?
A: It is renewable / they are carbon neutral (not adding more into atmosphere as it was already taken out) / no need to import D: A lot of it is needed for energy / A lot of room s needed to grow it
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What are the advantages of nuclear power?
Lots of energy without releasing a lot of CO2 / more energy than chemical reactions - less uranium required for the same level of power from coal / fuel = cheap / Lots of uranium
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What are the disadvantages of nuclear power?
power stations are difficult to maintain and build / Longer to start up / Processing uranium causes pollution / Risk of leaks or catastrophe / Radioactive waste = dangerous / Expensive to decommission / Uranium is finite
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What is the dynamo effect?
Using electromagnetic induction to transform kinetic energy into electrical energy
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What is electromagnetic induction?
The creation of a voltage (or current) in a wire which is experiencing a change in magnetic field
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What do you have to do to get a bigger voltage/current?
Increase strength of magnet / Increase number of turns on the coil / Increase the speed of movement
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Why do you need a high voltage to transport electricity around the country?
A high voltage means a lower current and so cables don't get as hot and less energy is wasted - more efficient / Cheaper for producers and customer
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How is electricity transported around the country?
From the generator, it is sent to the step-up transformer (up to 400,000V). It then travels along the cables and pylons before going to a step-down transformer. This lowers the voltage so that the electricity is safe to use
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What is the equation for energy efficiency?
Efficiency = ( Useful Energy Output / Total Energy Input ) x 100
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What is the equation for power? (If talking about electricity)
Power (W) = Voltage x Current
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What is the equation for energy supplied?
Energy Supplied (kWh) = Power (kW) x Time (hrs)
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What are the advantages of off-peak electricity?
Cost effective for the company - power stations cannot be turned off so it's good if there's demand at night / Cheaper for consumers to buy
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What are the disadvantages of off-peak electricity?
An increased risk of fire if appliances are kept on overnight / You start fitting your routine around the cheap-rate hours
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Explain the greenhouse effect
The Earth absorbs short EM radiation from Sun. Earth warms and emits some EM radiation. This tends to be infrared radiation. It is then absorbed by the gases in the atmosphere which re-radiate it in all directions inc. back to Earth - insulating
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How are humans causing an increase in the amount of greenhouse gases?
We travel more burning fossil fuels, more land is needed so trees which absorb CO2 are cut and burnt / Increase cattle = increase in methane, decaying landfills produce methane, naturally released / Power stations provide water vapour, natural source
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How are humans causing global warming?
We are releasing more CO2 into the atmosphere than is natural and so we are increasing the greenhouse effect. This means less heat is escaping and the Earth constantly gets warmer
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What may happen because of global warming?
Many regions will suffer more extreme weather e.g longer, hotter droughts. There would be more hurricanes and food production would be affected
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What can alpha radiation be used for?
It can be used for smoke detectors - the alpha source ionises the air and so a current flows between two electrodes. If there is a fire, the smoke absorbs the radiation ceasing the current so an alarm sounds
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What can beta radiation be used for?
As a tracer in medicine - can be monitored by a detector showing where the strongest reading is coming from / Thickness control - little beta paper = too thick rollers pinch tighter, loads beta paper = too thin rollers loosen
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What can gamma be used for?
High doses kill cells so can be used to treat cancer / by killing microbes, it can be used to sterilise equipment / non destructive testing - making sure airliners are safe
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Why are gamma waves and beta particles used in medicine?
Because they can leave the body and so are less likely to ionise nearby cells - they only choose materials that are radioactive for a few hours
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How do we create nuclear power?
Similar to a normal power station but with uranium as fuel. Uranium undergoes nuclear fission and in doing so a lot of heat is released. Water is used as a coolant. The heat produces steam which turns a turbine etc.
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How can nuclear fuel be used to make weapons?
Used uranium can be reprocessed again. This make more uranium which can be used to make more nuclear power and plutonium which can be used in weapons
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How can you protect yourself from radioactive sources?
Don't touch it - use tongs / Store sources in a lead box / Keep exposure time short / wear full protective suits / Lead-lined suits - lead-concrete barriers - lead screens / robot arms
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What are the different ways of disposing of radioactive waste?
Low-level waste can be buried in secure landfill sites / High-level waste is often sealed in glass blocks and buried deep underground in suitable place / Some waste can be reprocessed / Some waste is kept 'on-site'
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What are the dangers of radioactive waste?
If the canisters break, the waste could leak and contaminate groundwater harming soil, plants, animals and drinking water / Terrorists could use it to make a dirty bomb or contaminate our lifestyles or attack power plants
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Why doesn't the asteroid belt form a planet?
Jupiter has such as large gravitational field that it keeps interfering
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What happens if a meteorite hits Earth?
They can start fires / leave a giant crater / Dust and smoke are thrown up which can block out sunlight causing climate change and the death of species
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How can we tell meteorites have crashed in the past?
There are big craters / layers of unusual elements in rocks (imported by asteroids) / Sudden changes in fossil numbers between adjacent layers of rock as species suffer extinction
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What is a comet?
They are balls of rock, ice and dust which orbit the Sun in elongated elliptical orbits. As they approach the Sun, their ice melts leaving a bright tail of gas. Comets speed up as they get close to the Sun as the gravitational force is stronger
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What is Near-Earth Object?
NEOs are asteroids that pass within a third of the distance of the Earth from the Sun. They could collide with Earth and so powerful telescopes and satellites are used to monitor them
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What are they difficult to track?
They're small, dark and may have an unusual orbit. We use a bomb to nudge them off course if they are headed our way
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Where did the moon come from?
The theory is that a Mars sized planet collided with Earth. In the collision, the two dense iron cores merged into the Earth's core. Less dense material was ejected as hot dust and rocks. These orbited the Earth until gravity brought them together
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What evidence is there to back up the moon theory?
The Moon has a lower density and no iron core than compared to Earth / The Moon contains few substances which evaporate at low temperatures showing it was made from hot material
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What is a light year?
The distance light travels through a vacuum in one year. It is a measurement of distance and not time
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What are black holes?
When a star dies, it explodes. What is left is really dense and it has a strong gravitational attraction. They have a large mass and small volume but with high density. It's gravity is so strong, not even light can escape.
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How do we detect black holes?
Astronomers observe X-rays emitted by hot gases from other stars as they spiral into the black hole
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What are the advantages of unmanned probes?
They don't have to carry food, water and oxygen / They can withstand lethal conditions (e.g extreme heat, no air) / They're cheaper (less spent on safety) / If probe crashes, no one is hurt
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What are the disadvantages of unmanned space probes?
They cannot think for themselves (humans can overcome simple problems) / A spacecraft cannot do maintenance and repairs (if it breaks no one can fix it)
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What are the disadvantages of manned space travel?
A lot of food, water and oxygen has to be carried / temperature and toxic gases need to be regulated / shield needed to protect from radiation / psychologically stressful / muscle wastage
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What is red-shift?
When light waves appear to be stretching out as objects move away from us. The waves shift to the red part of the spectrum
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How do we know the universe is expanding?
Light from other galaxies is being red-shifted meaning that they are moving away from us. This means galaxies are moving away from each other, the further they are the faster they're traveling away and so the Universe must be expanding
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What is the theory of the big bang?
Around 15 billion years ago, all matter was at a single point (very hot and dense). There was an enormous explosion and a giant fireball of particles and radiation was released. It expanded rapidly and cooled.
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What is the life cycle of a star?
Clouds of dust and gas / Protostar / Main sequence star / Red giant / Planetary nebula / White Dwarf OR Red Supergiant / Supernova / Neutron Star / Black Hole
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What happens to during the main sequence of a star?
When the star is hot enough, the hydrogen nuclei undergo thermonuclear fusion which gives out masses of heat and light. It's stable as heat created provides an outward force that balances the force of gravity pulling everything inwards
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What happens to Red Giants?
As hydrogen runs out, the star swells. It then ejects it's outer layer of dust and gas to make a planetary nebula. This leaves a hot, dense core which cools and fades away
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What happens to Red Supergiants?
Red supergiants from heavier elements as in various nuclear reactions due to the star expanding and contracting several times due to more fusion. It eventually explodes throwing out dust and gas and leaving a dense core that may become a black hole
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What was the old theory of the Universe by Ancient Greeks?
They believed everything orbited the Earth in perfect circles - geocentric models
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What did the Copernican Model tell us?
Copernicus claimed that Earth and the planets orbited the Sun which was at the centre of the Universe in perfect circles - heliocentric model
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What did Galileo observe about Jupiter?
Galileo noticed 'stars' orbiting Jupiter which turned out to be moons showing not everything orbited Earth.
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What did Galileo observe about Venus?
Galileo observed that it had pases which would've been impossible ion the old model as Venus would've always been in front of the Sun however this could occur if Venus moved in front of and behind the Sun and so limiting what Earth could see lit
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Why were these condemned by the church?
The old models had been around for a long time / They went against the Bible which said Earth was the centre
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What do we believe now about the Universe?
We believe the planets in our solar system orbit the Sun. But theses orbits are elliptical and not circular
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Other cards in this set

Card 2


What are the advantages of using photocells?


They ahve no moving parts - they're sturdy, require low maintenance and last a long time / No power cables or fuel / Renewable energy source / Doesn't pollute enironment

Card 3


What are the disadvantages of using photocells?


Preview of the front of card 3

Card 4


What is a solar oven?


Preview of the front of card 4

Card 5


What is passive solar heating?


Preview of the front of card 5
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