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OCR Physics Module P2 LIVING FOR THE FUTURE P2a Collecting Energy from the Sun The Sun Photocells Photocells – advantages Photocells – disadvantages Photocell – energy transfer Photocell – power Passive solar heating – glass Solar reflector Wind turbines Wind turbines – advantages Wind turbines – disadvantages P2b Generating Electricity Dynamo effect Dynamo effect – increased Generator AC frequency Battery Electricity production – stages Power station Efficiency Energy input/output – equation Efficiency – equation Transformers Power transmission P2c Fuels for Power Fossil fuels Renewable biomass Nuclear fuel Uranium Ionising radiation Plutonium Nuclear power – advantages Nuclear power – disadvantages Power – unit Electrical appliances – cost Electrical appliances – power rating Unit of electricity Kilowatt hour Off-peak electricity – factors P2d Nuclear Radiations Ionising nuclear radiation Alpha (α) Beta (β) Gamma (γ) Penetrating power Background radiation Harmful effect Radioactive waste – disposal Radioactive waste – problems P2e Our Magnetic Field The Earth Earth’s core Magnets Cosmic rays Moving charged particles The Moon – origin The Sun Solar flares Solar flares – affects Artificial satellites stable source of energy; transfers energy to Earth as light and heat transfer light into electricity; produce direct current (DC); can operate in remote locations; have a power that depends on the surface area exposed to sunlight low maintenance; no need for power cables; no need for fuel; long life; rugged; renewable energy resource; no polluting waste no power at night or bad weather energy absorbed by photocell; electrons are knocked loose from the silicon crystal; electrons flow freely depends on: light intensity; surface area exposed glass is transparent to light; heated surfaces emit infrared; glass reflects infrared light reflected to a focus by a curved mirror; efficient solar collectors track Sun’s position in the sky transfer KE of air to electricity in wind turbines renewable; rugged; no polluting waste visual/noise pollution; depends on wind speed; needs space electricity can be generated by moving a coil near a magnet or moving a magnet near a coil to increase current; stronger magnets; more turns; faster movement alternating current (AC); coil of wire; magnetic field; coil and field close; relative motion between coil and field frequency of AC electricity is the number of cycles per second (Hertz, Hz); UK mains is 50Hz produces direct current (DC) source of energy; power station produces electricity; national grid (power lines connect station to consumers); consumers are homes, factories, offices and farms burning fuel; producing steam; spinning a turbine; turbine turns generator; significant energy waste some of the energy of the fuel in a power station is wasted as heat energy in the environmental fuel energy input = waste energy output + electrical energy output efficiency = electrical energy output ÷ fuel energy input increase or decrease voltage; electricity is transmitted at high voltage to reduce energy waste and costs increased voltage reduces current, so decreasing energy waste by reducing heating of cables crude oil, coal, natural gas (methane); burning fuels releases energy as heat wood, straw, manure; biomass fermented to generate methane. uranium fuel rods release energy as heat; radioactive waste: can be harmful; does not give rise to global warming non-renewable from radioactive waste can cause cancer waste product from nuclear reactors; can be used to make nuclear bombs independence from fossil fuels; high stocks of fuel; no greenhouse gases decommissioning costs; pollution from fuel processing; risk of accidental emission of radioactive material; high maintenance costs watt (W); kilowatt (kW) power rating in watts and kilowatts; the length of time it is switched on power (W) = voltage × current unit of electrical energy supplied is the kilowatt hour (kWh); energy supplied = power x time cost savings, convenience radiation knocks electrons off atoms (makes positive ions); electrons gained by atoms (makes negative ions) helium nucleus; used for smoke detectors electrons; used for tracers and paper thickness gauges very high frequency em radiation; used for treating cancer, non-destructive testing and sterilising equipment α stopped by paper; β stopped by thin aluminium; γ stopped by thick lead/concrete in the environment which is always present; from the Earth (air/rocks etc); Space (cosmic rays); human activity (nuclear explosions/accidents) radioactive materials give out nuclear radiation; damages living cells; cause cancers low level waste in land-fill sites; encased in glass and left underground; reprocessed radioactive for a long time; terrorist risk; must be kept out of groundwater; acceptable radioactivity level may change over time has magnetic field; shaped like bar magnet field; charged particles are deflected by magnetic fields contains a lot of molten iron have north and south pole; plotting compass shows the direction of a magnetic field ionising radiations from space; fast moving particles create gamma rays when they hit atmosphere; spiral around the Earth’s magnetic field to the poles; cause the Aurora Borealis electrical current (moving electrical charges) in a coil creates a magnetic field may be the remains of a planet which collided with the Earth; planets collide; their iron cores merge (forms the Earth); less dense material orbits as the Moon source of ionising radiation; causes solar flares that can interfere with the operation of artificial satellites clouds of charged particles from the Sun; ejected at high speed; produce strong disturbed magnetic fields satellite communications; electricity distribution Telecommunications; weather prediction; spying; (satellite) navigation systems P2f Exploring our Solar System The Universe Stars Planets Planet motion Planets motion – forces Radio signals Light-year Manned spacecraft – problems Unmanned spacecraft – advantages Unmanned spacecraft – problems Unmanned spacecraft – send data stars and planets; comets and meteors; black holes; large groups of stars called galaxies seen though they are far away because they are: very hot; give off their own light Mercury; Venus; Earth; Mars; Jupiter; Saturn; Uranus; Neptune; Pluto gravitational force determines the motion of planets and satellites gravity provides the centripetal force for orbital motion take a long time to travel through the solar system because of he distances measurement of very large distances; the distance light travels in a year enough fuel; long time required; effect of low gravity on health; shielding from cosmic rays; maintaining a stable atmosphere; providing enough food and water; keeping warm withstand conditions that are lethal to humans; safety; costs reliability; maintenance temperature, magnetic field and radiation; gravity, atmosphere and surroundings P2g Threats to Earth Asteroids Asteroids – orbit Asteroids – result of collision Asteroids – evidence of collision Comet Comet – approaches Sun Near Earth Object (NEO) Treat of NEO rocks; left over from the formation of the Solar System between Mars and Jupiter; large gravity of Jupiter disrupts the formation of a planet craters; ejection of hot rocks; widespread fires; sunlight blocked by dust; climate change; species extinction craters; layers of unusual elements in rocks; sudden changes of fossil numbers between adjacent layers of rock highly elliptical orbits; made from ice and dust; come from objects orbiting the Sun far beyond the planets strength of gravity increases; speed increases; brightness increases asteroid or comet on a possible collision course with Earth; can be seen with telescope surveys by telescope; monitoring by satellites; deflection by explosions P2h The Big Bang Big Bang theory Galaxies Big Bang – red-shift Big Bang – estimates Stars – life cycle Medium (Sun–like) star – end Heavy-weight star – end Black Hole origin of Universe; started with an explosion; Universe is still expanding moving away from us; distant galaxies moving away more quickly; microwave radiation received from all parts of the universe light from galaxies shifted to red end of spectrum; the further away galaxies are the greater the red shift the age and starting point of the Universe start as interstellar gas cloud; gravitational collapse makes protostar; thermonuclear fusion; long period of normal life (main sequence); end depends on mass of star red giant; planetary nebula; white dwarf red giant; supernova; neutron star or black hole large mass; large gravity; not even light can escape