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Physics 1a Summary


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As used in class- a summary

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Physics 1a Summary

  1. 1. Keywords: Conduction, convection, radiation, kinetic, gravitational, chemical, elastic Radiation Conduction-energy is transferred via particles colliding. It happens quicker Travel as waves, known as in solids due to particles being close thermal/infra red radiation. The together. It is quick in metals as heat from the sun electrons are free to move reaches us in this way, throughout metal. the waves can travel through a Convection- Liquids and gases expand when they are heated. The particles vacuum. move faster and the gap between particles widens. The liquid or gas in hot areas is less dense than the liquid or gas in cold areas, so it rises into the cold areas. The denser cold liquid or gas falls into the warm areas. In this way, Emitters of radiation convection currents are set up Heat Heat moves White/silver surfaces emit less thermal radiation. Polar bears are Types of Energy white so they emit less thermal -Light radiation. -Sound -Gravitational Potential (objects above the Earths surface have this) Reducing Heat Loss Examples -Electrical -Flasks have a vaccum layer so -Kinetic (moving) conduction and convection don’t -Chemical occur. Energy Efficiency -Silver materials used so less -Elastic (stretched or compressed objects) Efficiency = useful energy out thermal radiation emitted. -Thermal total energy in -Larger objects have a smaller -Nuclear surface area : volume ratio so less To convert to a percentage x 100! heat is lost. The Energy Law Energy can’t be created or destroyed it is just -Loft insulation as hot air rises Electrical Light 15J(useful) (convection) transferred into different forms. It is measured in Joules (J) 20J Heat 5J (wasted) -Double glazing has a layer of air as conduction is slower in gases. Efficiency = 15 20 =0.75 Electrical Heat (useful) Light/sound (wasted) Keywords: Efficiency, power, joule, nuclear, geothermal. Greenhouse effect, thermal, vacuum, renewable, turbine, generator.
  2. 2. Power Electricity Costs Fossil Fuels Coal (highest start up time), oil and gas Power (W)= energy (J) Measured in kilowatt-hours (kWh) the cost per unit also (shortest start up time). Disadvantages needs to be known. time (s) -Carbon dioxide produced –global warming Energy used (kWh) = power (kW) x time (hours) -Sulphur dioxide produced (acid rain) Power is the rate at which -Non renewable Take care with units! energy is transferred. 1 watt means 1 joule of Nuclear Wind energy is transferred every Chemical reactions involving uranium and Advantages – no Greenhouse gases produced, second. plutonium release heat which is used to renewable, no fuel costs boil water in power stations. Disadvantages – noise and visual pollution, won’t Advantages – no Greenhouse gases always work produced Disadvantages – non renewable, hazardous waste produced Geothermal which must be dealt with. Cold water is heated using rocks within the Earth, the resulting steam is used to drive Water (tidal, wave & hydroelectric) turbines. The movement of water is used to drive Advantages – renewable, no fuel costs, no turbines. harmful gases Advantages – no Greenhouse gases Disadvantages – very few suitable sites. produced, renewable, hydroelectric and Electricity and The National Grid tidal are reliable Colours 1- Fuel is burnt to heat water to make steam Disadvantages – can only be used in certain locations, loss of habitats and Dark colours absorb more heat. 2- The steam is used to spin a turbine farmland. Light colours reflect more heat 3-The spinning turbine spins a generator which produces electricity. Solar 4- The electricity goes to transformers to produce the Solar cells convert light into electricity. correct voltage Solar panels are used to heat water Step up transformers increase the voltage, step down Advantages – renewable, no fuel costs, transformers reduce voltage. The National Grid carries no harmful gases produced energy at a low current as this means less energy is lost as Extra Notes heat, but it requires a high voltage. Disadvantages – expensive and inefficient, need a sunny climate, won’t work at night.