P2 Flashcards
What is a photocell?
A photocell is a device that generates electricity from light.
What are the advantages of photocells?
The advantages of photocells are:
- They can be used in remote locations.
- They do not emit CO2 or greenhouse gases.
- The energy source is free.
- The energy source is renewable.
What are the disadvantages of photocells?
The disadvantages of photocells are: They can’t be used at night or in bad weather.
What sort of electricity do photocells produce?
Photocells produce Direct Current or D.C. electricity.
How could you increase the electricity generated in a photocell?
To get more electricity from your photocell you could:
- have brighter light or
- a greater surface area or
- be closer to the light source.
Explain how photocells produce electricity.
- Light energy is absorbed by photocell.
- Electrons are knocked loose from the silicon atoms in the crystal.
- Electrons flow freely.
- This flow of electrons is the current.
Describe what is meant by passive solar heating.
- Glass is transparent to the Sun’s radiation.
- Heated surfaces emit infrared radiation of longer wavelength.
- Glass reflects this longer wavelength infrared, keeping the heat inside.
How can you make a solar collector even more efficient?
Efficient solar collectors track the position of the Sun in the sky.
How else can we use the Sun’s energy?
We can use the Sun’s energy by collecting it on a curved mirror. This can be used for solar cooking or generating a very high temperature.
How does the Sun cause the wind?
Heat from the Sun produces convection currents in the air. This is the wind!
Give some advantages and disadvantages of wind energy.
Advantages:
- renewable energy source
- no greenhouse gases produced (such as carbon dioxide)
Disadvantages
- visual pollution (people don’t like the look of them)
- take up a lot of land
- don’t produce energy if there’s no wind
How do you generate electricity?
You can generate electricity by moving a magnet near a wire or a wire near a magnet.
What’s the difference between the electricity produce by a battery and the elctricity produced by a generator?
Batteries produce direct current (D.C.) and a generator produces alternating current (A.C.)
How could you get a generator to produce more elctricity?
A generator will produce more electricity if:
- there is a stronger magnet or
- the coil is moved faster or
- there are more turns of wire on the coil
Describe how electricity is generated at a conventional power station.
Burning fuel produces steam. Steam spins a turbine. Turbine turns a generator
In a power station, not all the energy you put in comes out as useful energy. How do we measure this lost energy?
Efficiency gives us a measurement of how much energy is wasted in a power station.
Which gases are classed as greenhouse gases?
3 greenhouses gases are carbon dioxide water vapour and methane.
Explain how these gases cause the greenhouse effect.
- Short wavelength e-m radiation from the Sun is absorbed by the Earth and heats the Earth up.
- The Earth radiates heat as longer wavelength infrared radiation.
- Greenhouse gases absorb some infrared radiation, warming the atmosphere.
What are the man-made causes of climate change?
Gases, such as CO2, released from factories and vehicles because of combustion.
What natural events can cause changes to weather patterns?
Volcanic ash and gases reflecting radiation from the Sun back into space causing cooling.
Why do scientists share data about global warming?
Scientists share data so that other scientists can check their results and so that governments and the public can take action if necessary.
Whys do some people think global warming is not a result of human activity?
The climate has changed many times throught history, so some people think this is just part of a natural cycle.
Name some fossil fuels used in power stations.
Coal, oil and gas are all fuels used in power stations.
What renewable fuels might be burned in power stations.
Biomass (biological material) such as wood, straw or even manure can be burnt in power stations.
What fuel is used in nuclear power stations?
Uranium, sometimes plutonium, is used in nuclear power stations.
What is power measured in?
Power is a measurement of how quickly energy is transferred. It is measured in Watts (W). 1 Watt means 1 Joule per second.
How many Watts in a kilowatt?
1000! There are 1000 anything in a kilo anything!!
What’s the relationship between power, voltage and current?
Power = voltage x current
What are the advantages of using fossil fuels in power stations?
Fossil fuels are relatively cheap and easy to transport. They contain lots of energy and the technlogy needed is simple.
What are the disadvantages of using fossil fuels in power stations?
Fossil fuels produce carbon dioxide when burnt which adds to the greenhouse effect. Coal produces sulphur dioxide which can cause acid rain. They are non-renewable and we will run out of them eventually.
What are the pros and cons of nuclear power?
Pros: No greenhouse gases as nothing is burnt. Fuel contains lots energy.
Cons: Produces radioactive waste material. The fuel, uranium, is non-renewable.
What’s a kilowatthour?
1 kWhr is the energy used if a 1kW appliance is used for 1 hour.
What’s a unit of electricity?
One unit is the same as 1 kWhr (kilowatthour)
How would you work out the cost of using electricity?
To work out the cost, first calculate the number of units or kilowatt hours used, then multiply by the cost per unit.
What do transformers do?
Transformers increase or decrease voltage.
Why are transformers used in the National Grid?
Electrical energy is transmitted at high voltage to reduce energy waste and costs.
Why does a higher voltage in electricity transmission reduce waste?
Because power = voltage x current we can have the same power at a lower current if we make the voltage high. A low current is good because then the wires don’t get so hot and waste energy as heat.
Name the three types of nuclear radiation.
The 3 types of nuclear radiation are alpha beta and gamma.
Give an example of a use of alpha radiation.
Alpha radiation is used in smoke detectors.
Give an example of a use of beta radiation.
Beta radiation is used for measuring the thickness of paper or foil.
Give an example of a use of gamma radiation.
Gamma radiation is used for treating cancer, in tracers, and for sterilising.
Why is nuclear radiation dangerous?
Nuclear radiation is dangerous because it damages living cells and can kill them or cause cancers.
Radiation can be ionising. What does this mean?
Radiation can cause atoms to lose or gain electrons. This is ionisation.
What stops alpha beta and gamma?
Alpha radiation is stopped by a piece of paper.
Beta is stopped by a few mm of aluminium.
Gamma can be stopped by a few cm of lead or a few metres of concrete.
How can you stay safe when handling radioactive material?
To protect yourself from radioactive material:
- wear protective clothing
- use tongs / keep your distance
- short exposure time
- shielded and labelled storage.
Describe some ways of disposing of radioactive waste.
- low level waste in land-fill sites
- waste is encased in glass and left underground
- waste can be reprocessed.
Explain the problems of dealing with radioactive waste.
- remains radioactive for a long time
- terrorist risk
- must be kept out of groundwater
- acceptable radioactivity level may change over time.
What’s the difference between a start and a planet?
Stars give off their own light and planets only reflect light. Planets orbit stars.
What’s a galaxy?
A galaxy is a group of billions of stars.
Put these in order of size, biggest first: star, planet, galaxy, solar system, universe, meteors, comets
Universe, galaxy, solar system, star, planet, comet, meteor.
Planets travel in roughly circular orbits. What’s the name of a force that pulls sonething round in a circle?
The force that pulls things round in a circle is called centripetal force.
What is the centripetal force that keeps planets going round stars?
Gravity acts as the centripetal force keeping planets going round stars, or the moon going round the Earth.
What’s a light year?
A light year is the distance that light travels in a year.
What are the advantages and disadvantages of manned speacecraft?
Advantages are that humans can carry out experiments and make direct observations. Humans may be able to fix things or change plans.
The disadvantages are that you need to carry food and oxygen so need more space and fuel. The spacecraft would not be able to go as far or for as long a time. An unmanned spacecraft could be sent into hot or cold conditions that would kill a human.
How do scientists think the moon was formed?
A collision between two planets can result in an Earth-Moon system:
• the planets collide
• their iron cores merge to form the core of the Earth
• less dense material orbits as the Moon.
What is the evidence that the moon was formed by a collision between two planets?
The moon has no iron core and is only made from less dense rocks, but these rocks are similar to those found on Earth.
What’s an asteroid?
An asteroid is a rock that is in orbit around the Sun.
Where is the asteroid belt?
The asteroid belt is in between Mars and Jupiter.
>
Why is the asteroid belt is in between Mars and Jupiter?
The asteroid belt is in between Mars and Jupiter because the strong gravitational field of Jupiter stops the formation of a planet.
What would happen if an asteroid collided with the Earth?
Some of the consequences of a collision with a large asteroid:
• crater
• ejection of hot rocks
• widespread fires
• sunlight blocked by dust
• climate change
• species extinction.
Describe some of the evidence for past asteroid collisions.
Layers of unusual elements in rocks.
Sudden changes in fossil numbers between adjacent layers of rock.
Describe the make up of a comet.
Made from ice and dust.
Has a tail formed from a trail of debris.
What can you say about a comet’s orbit?
The orbit of a comet is higly elliptical and the comet coems from out beyond the planets and orbits the Sun. It speeds up as it approaches the Sun because the gravitational pull is stronger as you get closer.
What is an NEO?
NEO stands for Near Earth Object - an object from space which may come close to the Earth.
What possible actions could be taken to reduce the threat of NEOs?
The possible actions which could be taken to reduce the threat of NEOs are:
• surveys by telescope
• monitoring by satellites
• deflection by explosions (when they are distant enough from Earth).
What is meant by the Big Bang?
The Big Bang is the theory that the Universe started with an explosion and that the universe is still exapnding as a result.
What evidence is there for the Big bang?
The evidence for the Big Bang is:
most galaxies are moving away from us.
distant galaxies are moving away more quickly.
microwave radiation is received from all parts of the Universe.
What is red shift?
Red shift is the way that light from objects moving away from us gets stretched and so looks redder. The faster they move away, the bigger the red shift. Red shift is evidence for the expanding Universe.
What do stars begin their life as?
Stars begin their lives as clouds of dust and gas called nebulae, that form protostars as gravity pulls the material in and compresses it. Nuclear fusion starts and the star ten enters its main stage, like our Sun.
Describe the end of the ‘life cycle’ of a small star.
The end of the ‘life cycle’ of a small star:
• red giant
• planetary nebula
• white dwarf.
Describe the end of the ‘life cycle’ of a large star.
The end of the ‘life cycle’ of a large star:
• red supergiant
• supernova
• neutron star or black hole (for massive stars).
What is the Ptolemeic model of the Universe?
The Ptolemeic model of the Universe is that everything revolves around the Earth. The Earth is the centre of the Universe.
What is the Copernican model of the Universe?
The Copernican model of the Universe is that the Sun is the centre of the solar system and that the planets revolve around the Sun.
What did Galileo use to help gain eveidence for the Copernican or geocentric (Earth centred) model?
Galileo used a telescope to observe the movement of the planets and moons. He showed that not everything went round the Sun.
Why were the theories of the Copernicus and Galileo models considered controversial when they were announced, and not widely adopted until many years had passed?
The church had strong views about the Earth being at the centre of everything. Because the church was very powerful any views other than this were ignored or seen as controversial.
