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FlashCards por aneeqaahmed, atualizado more than 1 year ago
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Criado por aneeqaahmed
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| Questão | Responda |
| Physics: Living for the future (Energy Resources) P2 Flash Cards | By Aneeqa Ahmed |
| Advantages of Photocells | The advantages of Photocells are: They are robust and don't need much maintenance, don't need fuel and don't need long power cables, cause no pollution and don't contribute to global warming and they use a renewable energy resource. |
| Disadvantages of Photocells | They do not produce electricity when it is too dark or cloudy. |
| How photocells work (Stage 1 + 2) | 1. A photocell contains two pieces of silicon joined together to make a p-n junction. 2. One piece has an impurity added to produce an excess of free electrons -n type silicon. |
| How photocells work (Stage 3 + 4) | 3. The other piece has a different impurity added to produce an excess of free electrons - p type silicon. 4. Sunlight contains energy packets called photons. |
| What a Photon is | Photons cause free electrons to move producing an electric current. |
| What the output from a photocell depends on: | 1. The light intensity. 2. The surface area exposed. 3. The distance from the light source. |
| Passive Solar Heating 1 | The sun is very hot and produces infrared radiation with a very short wavelength. Glass is transparent to this short wavelength radiation. |
| Passive Solar Heating 2 | The walls and floor inside a building absorb this radiation, warm up and re-radiate infrared radiation. The walls and floors aren't as hot as the sun and the wavelength radiated is therefore longer. |
| Passive Solar Heating 3 | Glass reflects this longer wavelength radiation back inside the building. In the southern hemisphere the big windows in a house face north towards the sun and in the northern hemisphere they face south. |
| Heat from the sun | Solar reflectors are moved by computer to make sure they are always facing towards the sun. |
| Energy from the wind: | Wind is a renewable form of energy, but it does depend on the speed of the wind. Wind turbines don't work if there is no wind, nor if the wind speed is too great. |
| Wind Farms - (Advantages and Disadvantages) | Advantages: They don't contribute to global warming, nor do they pollute the atmosphere. Disadvantages: They can be noisy, take up a lot of space and people sometimes complain about the view being spoiled. |
| How a current from a dynamo can be increased | This can be increased by: Using a stronger magnet, Increasing the number of turns on the coil and Rotating the magnet faster. |
| What is an OSCILLOSCOPE | This is the output from a dynamo which can be displayed on one of these. An oscilloscope trace shows how the current produced by the dynamo varies with time. The time 1 complete cycle is called the period of the alternating current. |
| Simple Generators | This consists of a coil of wire rotating between the poles of a magnet: The coil cuts through the magnetic field as it spins. A current is produced in the coil. |
| How a Current can be produced. | It can be produced if the coil remains stationary and the magnets move. (Generators at power stations work on the same principle) |
| Power Stations | In conventional power stations, fuels are used to heat water: Water boils to produce steam, steam at high pressure turns a turbine and the turbine drives a generator. |
| Energy Efficiency | Efficiency is a measure of how well a device transfers energy. Energy in a power station is lost in the boilers, generators and cooling towers. |
| Greenhouse gases 1 | Most wavelengths of electromagnetic radiation can pass through the earth's atmosphere, but infrared radiation is absorbed. |
| Carbon Dioxide occurs naturally because of: | Natural forest fires, volcanic eruptions, decay of dead plant and animal matter, its escape from the oceans and respiration. (Manmade carbon dioxide is caused by burning fossil fuels, waste incineration, deforestation and cement manufacture. |
| Water Vapour | This is the most significant greenhouse gas: Almost all of the water vapour occurs naturally, about 0.001% comes from human activities and 1/2 of the greenhouse effect is due to water vapour and a 1/4 due to clouds. |
| Greenhouse Gases 2 | Methane is produced when organic matter decomposes in an environment lacking oxygen. Natural sources include wetlands, termites and oceans. Man-made sources include the mining and burning of fossil fuels, digestive processes of animals (cattle), rice paddies and waste in landfills. |
| The Greenhouse Effect | The electromagnetic radiation from the sun has a relatively short wavelength. This is absorbed by and warms the earth, the earth then re-radiates the energy as infrared radiation with longer wavelength. The longer wavelength radiation is absorbed by greenhouse gases which warms the atmosphere. |
| Dusts in the atmosphere | This can have opposite effects: The smoke from factories reflects radiation from town back to earth, the temp rises. The ash cloud from a volcano reflects radiation from sun to space, temp falls. |
| Measuring Power | Electrical appliances usually display a power rating in watts (W) or kilowatts (KW). The unit of electrical energy used in the home is the kilowatt-hour (KWH). |
| Measuring Power (Equations) | Power = Voltage x Current Energy Supplies = Power x Time Cost of Electricity used = Energy Used x Cost per KWh |
| Cheaper Electricity | We pay less for the electricity during the night, when much isn't needed but it still has to be produced. |
| Energy Sources | Some energy sources are more appropriate than others in a particular situation because of the factors below: availability, ease of extraction, effect on the environment and associated risks. |
| The National Grid | This is a series of transformers and power lines that transport electricity from power stations to the consumer. High voltage leads to - Reduced energy loss, reduced distribution costs and cheaper electricity for consumers. |
| Transmission Losses | When a current passes through a wire it gets hot. The greater the current, the hotter the wire. When a transformer increases the voltage, current is reduced means less heating effect, less energy lost to the environment. |
| Ionisation 1 | Atoms contain the same number of protons and electrons - they are neutral. Ionisation involves gaining or losing electrons: When the atom gains electron it is negatively charged and when electrons are lost it is positively charged. |
| Formation of Ions | This can cause chemical reactions. Such reactions may disrupt the normal behaviour of molecules in the body. This can cause strands of DNA to break or change; Protein molecules may change their shape and these effects are potentially harmful. |
| Properties of Ionising Radiation 1 | 1. Alpha, Beta and Gamma radiations come from the nucleus of an atom. 2. Alpha radiation causes most ionisation and gamma radiation cause the least. |
| Properties of Ionising Radiation 2 | 3. Alpha Radiation is short ranged (a few centimetres) and is easily absorbed by a sheet of paper or card. 4. Beta Radiation has a range of about 1m and is absorbed by a few millimetres of aluminium. |
| Property of Ionising Radiation 3 | 5. Gamma radiations is more penetrating, a few centimetres of lead would stop radiation, some can pass through several metres of lead or concrete. 6. Experiments can be done to check the penetration, check background radiation. |
| Uses of Radioactivity Smoke Alarms (Alpha Radiation) | They contain a source of Alpha Radiation, the radiation ionises the oxygen and nitrogen atoms in the air which causes small electric currents. When smoke fills the detector during a fire the air isn't ionised so the current is less and the alarm makes a sound. |
| Uses of Radioactivity Paper rolling Mill (Beta Radiation) | Thickness in a paper rolling mill can be controlled using a source of beta radiation and a detector: The amount of radiation passing through the sheet is monitored and the pressure on the rollers adjusted accordingly. |
| Uses of Radioactivity Sterilising Medical Instruments (Gamma radiation) | Gamma radiation kills microbes and bacteria so it can be used for sterilising medical instruments. It can also be used to check for leaks in pipes or welds. (Passage of blood and other substances can be traced by Gamma and Beta sources. |
| Nuclear Waste | Plutonium is a waste product from nuclear reactors which can be used to make nuclear bombs. Some low level radioactive waste can be buried in landfill sites, high level waste is encased in glass and buried seep underground or reprocessed. |
| Radioactive Waste | This can remain radioactive for thousands of years. it must be stored where it cannot leak into natural underground water supplies and hence into lakes and rivers. It is not suitable for making nuclear bombs but can be used by terrorists to contaminate water supplies or land. |
| Advantages and Disadvantages of Nuclear Power Stations | Advantages: Fossil fuel reserves are not used and no greenhouse gases are discharged into the atmosphere. Disadvantages: Very high maintenance and decommissioning costs, risk of accidents. |
| Comets | They have very elliptical orbits: They pass inside the orbit of Mercury and go out well beyond the orbit of Pluto. |
| Meteor | A Meteor is made from grains of dust that burn as they pass through the Earth's atmosphere: They heat the air around them which glows and the streak is known as a 'Shooting Star' |
| Black Holes | Black Holes are formed where large stars used to be: You cannot see a black hole because light cannot escape from it. It has a large mass but a very small size. |
| Centripetal Force | Moons orbit planets and planets orbit stars because of this force acting on them. 1. Centripetal Force acts towards the centre of the circular orbit. 2. Gravitational attraction is the source of the centripetal force. |
| Exploring the Planets | Unmanned probes can go where conditions are deadly for humans. Spacecrafts carrying humans have to have large amounts of food, water and oxygen aboard. |
| Astronauts (Clothing in Space) | They can wear normal clothes in a pressurised spacecraft. Outside the spacecraft they need to wear special space suits for example: A dark visor (stops becoming blind), Suit (has source of oxygen for breathing). |
| Space 1 | When travelling in space, astronauts are subjected to lower gravitational forces. Unmanned spacecraft cost less and don't put lives at risk, the spacecrafts need to be reliable because there is usually no way of repairing them when they break down. |
| Space 2 | All bodies in space, including planets were formed when clouds of gas and dust collapsed together due to gravitational forces of attraction. The mass of an object determines its gravitational force. |
| Distances in Space | Distances are very large. Light travels at 300 000 km/s : light from the sun takes about 8 minutes to reach us on earth. Light from the nearest star takes 4.22 years approximately. (A light year is the distance light travels in one year) |
| Asteroids | Asteroids are mini planets or planetoids orbiting the sun: - Most orbit between Mars and Jupiter - Are large rocks that were left over from the formation of the Solar System. |
| Origin of The Moon 1 | Scientists believe our Moon was a result of the collision between 2 planets in the same orbit. The iron core of the other planet melted and joined with the Earth's core, less dense rocks began to orbit and they joined together to form our moon. |
| Origin of The Moon 2 | There is scientific evidence to support this: - The average density of the Earth is higher than the density of the Moon. - There is no iron in the Moon. - Moon has the same oxygen composition as the Earth, but rocks on Mars and other parts have different oxygen composition. |
| Comets Orbit (Most Comets pass inside the orbit of Mercury and well beyond the orbit of Pluto) | As the Comet passes close to the sun, ice melts and solar winds blow the dust into the comets tail which faces away from the sun. Scientists constantly monitor these and other near-Earth objects. The speed of a comet increases as it approaches the sun and decreases away. (gravitational) |
| NEO's (Near-Earth Objects) | If an NEO is on a collision course with Earth it could be the end of life on Earth. To avoid this, 1 option would be to explode a rocket near to the NEO which could alter its course enough to miss Earth. |
| The Universe | Expanding - Almost all of the galaxies are moving away from each other with further galaxies moving faster. |
| Definition of The Red Shift | When a source of light is moving away from an observer, its wavelength appears to increase which shifts light towards the red end of the spectrum. |
| Nebula | This is a swirling cloud of gas and dust |
| Nebula Clouds | They are pulled together by gravity and, as the spinning ball of gas starts to get hot, it glows. This protostar cannot be seen because of the dust cloud. |
| Gravity and Stars | Gravity causes the star to become smaller, hotter, brighter and after millions of years. The core temperature is hot enough for nuclear fusion to take place, as hydrogen nuclei join together to form helium nuclei, energy is released and the star continues to shine while there is enough hydrogen. |
| A star's life history (Small Stars) | Small Stars shine for longer than large stars because they have less hydrogen but use it up at a slower rate and what happens at the end of a star's life depends on its size. |
| The end of a star's life (Medium Sized Star) | A medium sized star like the sun becomes a red giant, while the core contracts, the outer part cools and changes colour from yellow to red and expands. Gas shells called planetary nebula are thrown out, the core is a white dwarf shining brightly but becomes a black dwarf by cooling. |
| The end of a star's life (Large Stars) | Become red supergiants, as core contracts, the outer expands, the core collapses to form a neutron star and there is an explosion called a supernova. neutron stars are dense, remnants from a supernova merge to create new stars and the core continues to collapse, more dense |
| The end of a star's life (Black Hole) | Large star's could form a black hole. A black hole has a very large mass concentrated in a small volume so it has a very large density and its large mass means it has a strong gravitational pull. |
| Stars | They are formed from nebulae and will eventually become: Red giants White dwarfs finally, Black dwarfs |
| Asteroids | Most asteroids orbit between Mars and Jupiter but some pass closer to the Earth. Constantly being monitored. An asteroid strike could cause climate change and species extinction |
| The Universe | It is explored by telescopes on the Earth and in Space. Large distances mean that it takes longer for information to be received and inter-galactic travel unlikely. |
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