384465
Descripción
Fichas por Anna Hollywood, actualizado hace más de 1 año
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Creado por Anna Hollywood
hace casi 11 años
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| Pregunta | Respuesta |
| What are the 4 advantages of photocells? | -Robust and don't need much maintenance -Don't need fuel or power cables -Don't cause pollution -Use a renewable energy source |
| What is the only disadvantage of photocells? | Don't produce electricity when it's dark or too cloudy |
| What do photocells contain? | Two pieces of silicon joined together to make a p-n junction |
| Which has an impurity added to produce an excess of free electrons and which one has an impurity added to produce an absence of free electrons? | n-type = excess p-type = absence |
| What does sunlight contain? | Photons |
| What do photons cause? | Free electrons to move, producing an electric current |
| What are the 3 things that the output from a photocell depends on? | -light intensity -surface area exposed -distance form light source |
| How does passive solar heating work? | -Glass is transparent to suns short wavelength radiation -Walls and floors absorb radiation, warm up then re-radiate infrared -Re-radiated wavelength is longer as walls are not as hot as the sun -Glass reflects the longer wavelength back into building |
| How are solar reflectors so efficient? | Computer controlled so are always facing the sun |
| When do wind turbines not work? | Not enough wind/wind speed is too great |
| What are the advantages and disadvantages of wind farms? | + don't contribute to global warming + don't pollute - noisy - take up lot of space - can spoil view |
| What are the 3 ways in which the current from a dynamo can be increased? | -Stronger magnet -More turns on coil -Rotating magnet faster |
| What does an oscilloscope do? | Shows dynamo current change |
| What is the time for one complete cycle called? | Alternating current |
| What does a simple generator consist of? | Coil cuts through the magnetic field as it spins, a current is produced in the coil |
| Where are the structure of simple generators used? | In the generators at power stations |
| How do conventional power stations work? | Water boils to produce steam, steam at high pressure turns a turbine and the turbine drives a generator |
| Why are power stations not very energy efficient? | Lose energy through boilers, generators and cooling towers |
| What type of radiation is absorbed by the earth's atmosphere? | Infrared radiation |
| What are the 5 things that produce carbon dioxide? | -natural forest fires -volcanic eruptions -decay of dead plant and animal -its escape from the oceans -respiration |
| What are the 4 man made things that produce carbon dioxide? | -Burning fossil fuels -Waste incineration -Deforestation -Cement manufacture |
| 3 facts about water vapour | -almost all of it occurs naturally -0.001% comes from human activity -half of the greenhouse effect is due to water vapour and a further quarter due to clouds |
| When is methane produced and give 2 examples of this | When organic matter decomposes in an environment lacking oxygen. Natural sources (wetlands, termites and oceans) and man-made sources (mining, burying of waste in landfills) |
| Explain the greenhouse effect | The radiation from the sun is absorbed by the Earth, the earth re-radiates the energy as infrared radiation with a longer wavelength. These longer wavelengths are absorbed by the greenhouse gases which warms the atmosphere |
| What does smoke from factories do? | Reflect the radiation from the town back to Earth, causing the temperature to rise |
| What does the ash cloud from volcanoes do? | Reflects radiation from sun back into space, causing the temperature to fall |
| What do scientists agree on to do with global warming? | That the average temperature over the past 200 years has risen due to climate change |
| What do scientists disagree on to do with global warming? | The extent to which human activity has contributed |
| When do we pay less for electricity? | At night |
| What are the 4 things that the choice of energy source depends on? | -availability -ease of extraction -effect on the environment -associated risks |
| What is the National grid? | A series of transformers and power lines that transport electricity from the power station to the consumer |
| What does the high voltage lead to? (3 things) | -reduced energy loss -reduced distribution costs -cheaper electricity for consumers |
| What are used to step down the voltage to a more suitable level for the consumer? | Transformers |
| Why is a higher voltage used? | Because this decreases the current to prevent energy loss (from heating the wires) |
| What does ionisation involve? | Gaining or losing electrons |
| What can the formation of ions cause in the body? | Chemical reactions such as strands of DNA to break or change; or protein molecules to change shape, possibly causing harm |
| Where do alpha, beta and gamma radiations come from? | The nucleus of an atom |
| Which causes the most ionisation? | Alpha |
| What is alpha radiation's range and what does this cause to happen? | A few centimetres so it is easily absorbed by a sheet of paper/card |
| What is beta radiation's range and what does this cause to happen? | About 1 metre and so is absorbed by a few millimetres of aliminium |
| What is gamma radiation's range and what does this cause to happen? | Much more penetrating and although a few cm of lead may stop some of the radiation, some can pass through several metres of lead or concrete |
| How do smoke alarms use radiation to detect smoke? | The alpha radiation ionises the oxygen and nitrogen atoms in the air causing a small current. When there is smoke the oxygen and nitrogen don't get ionised, causing the circuit to break and the alarm to go off |
| How can radiation be used to control the thickness of paper? | They use beta radiation and a detector, the amount of radiation passing through the sheet is monitored and the pressure on the rollers adjust accordingly |
| What can gamma radiation be used for? | Killing microbes and bacteria on medical equipment. It can be used to check for leaks in pipes and welds too. |
| What can the passage of blood around the body be detected using? | Beta and gamma radiation |
| What is plutonium? | A waste product from nuclear reactors which can be used to make nuclear bombs |
| How do you dispose of low level and high level radioactive waste? | Low level can just be buried in landfill but high level is encased in glass and buried deep underground. |
| Why is the storage and disposal of radioactive waste very important? | It remains radioactive for thousands of years and must be stored where it cannot leak into water supplies. It can be used by terrorists to contaminate water supplies too. |
| What are the two advantages of using nuclear power stations? | -Fossil fuels aren't used -No greenhouse gases are made |
| What are the three disadvantages of using nuclear power stations? | -High maintenance -Decommissioning costs -Risk of accidents are devastating |
| What types of orbits do comets have? | Elliptical |
| What are meteors made out of? | Grains of dust that burn up as they pass through the earth's atmosphere. They heat the air around them which glows (a shooting star) |
| What are black holes? | Formed where large stars used to be. You can't see a black hole because light can't escape from it and it has a huge mass but is small in size |
| Why do moons orbit planets? | Because of the centripetal force acting on it |
| What can we send up to explore space? | Unmanned probes |
| What do spacecraft carrying humans have to have a lot of? | Food, water and oxygen |
| What are the 4 things that an astronauts suit has to do? | -a dark visor to stop them being blinded -pressurised suit with oxygen supply -the surface of the suit facing the sun has to be tolerant of temperatures up to 120 degrees -the surface of the suit facing away from the sun has to be tolerant of temperatures up to -160 degrees |
| Why are unmanned spacecraft often better? | Doesn't put astronauts lives at risk (but they have to be very reliable as they can't be repaired once in space) |
| How fast does light travel? | 300,000km/s |
| How long does light take to reach the earth from the sun? | 8 minutes |
| How much does it cost to fly to Mars (according to America's planned trip)? | £400 billion |
| What are asteroids? | Mini planets orbiting the sun left over from the formation of the solar system |
| What caused all bodies in space to be created? | When clouds of gas and dust collapsed together due to gravity |
| What determines something's gravitational force? | The mass |
| What prevents asteroids from joining together to form another planet? | Jupiter's gravitational force |
| How do scientists think the moon was made? | The collision of two planets. The iron core of one planet collided with the Earth's core then less dense rock began to orbit, forming the moon. |
| What are the 3 pieces of evidence that support the theory of how the moon was created? | -Avg. density of earth is 5500kg/m3 and the moon is 3300kg/m3 -There is no iron in the moon -The moon has same oxygen composition as Earth (unlike other planets) |
| What are the 3 pieces of evidence that support the theory that asteroids have collided with the Earth? | -near to crater they found quantities of the metal iridium (normally found in meteorites) -many fossils are found below the layer of iridium (not many found above) -tsunamis have disturbed fossil layers |
| Where do most comets pass? | Inside the orbit of Mercury and well beyond the orbit of Pluto |
| What happens as the comet passes close to the sun? | The ice melts and solar winds blow the dust into the comets tail which always points away from the sun |
| What are scientists constantly tracking? | The paths of comets and other NEOs |
| Why does the speed of a comet increase as it approaches the sun and decrease as it gets further away? | Because of the changing gravitational attraction |
| What shape is a comets orbit? | Elliptical |
| What happens if an NEO is heading for earth? | A rocket may be exploded near it which should alter its course enough to miss the Earth |
| In what way is the universe expanding? | The galaxies are always moving away from each other and the furthest galaxies are moving the fastest |
| How did Galileo's observations help support Copernicus' ideas? | Galileo observed four moons orbiting Jupiter, supporting the theory that not everything orbits the earth, but the sun |
| Why didn't the Roman Catholic Church support Galileo's model? | Because it went against their ideas that the Earth was the centre of the universe |
| What was Newton working on in the 17th century? | His theory of universal gravitation, suggesting that all bodies attract one another |
| Why do we believe that the gravitational collapse of the universe is prevented? | As the universe is constantly expanding as a result of the Big Bang |
| What is red shift? | When a source of light is moving away from something, its wavelength appears to increase which shifts the light towards the red end of the spectrum |
| What is the difference between the light pattern observed form the sun and from a distant star? | The light from the star is closer to the red end of the spectrum |
| What can scientists use red shift to find out? | The age of the universe |
| What is the swirling cloud of gas and dust? | A nebula |
| Explain a star's life | -nebula cloud pulled together by gravity -this protostar gets hot & glows -gravity makes star get smaller hotter and brighter -after millions of years it's so hot that nuclear fusion occurs -hydrogen nuclei join to form helium nuclei -energy is released and the star shines while there is enough hydrogen |
| Why do small stars shine for longer than large stars? | They have less hydrogen but use it up at a slower rate |
| How does a medium stars life end (like the sun)? | Becomes a red giant: core contracts, outer part cools, changes from yellow to red and expands. Planetary nebula (gas shells) thrown out, core becomes white dwarf shining bright then becomes a black dwarf |
| How does a large star's life end? | Become red supergiant: core contracts, outer part expands, suddenly core collapses to form a neutron star - explosion (supernova). |
| What can happen in the aftermath of a supernova? | -neutron stars are very dense -remnants can merge to form new star -core of neutron star keeps collapsing, getting denser to form black hole |
| What are the properties of a black hole? | -Large mass -Small volume -Very large density -Large mass=strong gravitational pull |
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