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67 Cards in this Set
- Front
- Back
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What are the different ways of transferring energy? |
Radiation - Transfer by infrared radiation Conduction - Solids Convection - Liquids + Gases Infrared radiation - All states, any object can absorb + emit radiation. Bigger temperature difference = faster energy transfer. |
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Which types of materials absorb + reflect better? |
Dark matt absorb + emit better Light shiny reflect better |
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How do solar hot water panels work? |
They contain pipes under a black surface, to heat them faster. |
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What are the properties of the different states of matter? |
Solid - Strong forces, fixed, regular arrangement, vibrate (little energy) Liquid - Weaker forces, irregular arrangement, random, slow movement Gas - No forces, free movement, random, high speed |
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What is conduction? |
Vibrating particles pass on extra kinetic energy to neighbouring particles. Faster in denser solids. Insulators have larger spaces between particles. |
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Why do metals conduct well? |
They have free electrons, which can move faster so can pass heat energy around the metal faster. |
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What is convection? |
Energetic particles move from the hotter region to the cooler region. |
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How do immersion heaters work? |
Heat travels to coil by conduction Water gains more energy, moves faster and becomes less dense Hotter water rises above the cooler water which is pushed to the heater coil |
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What are convection currents about? (I.e. where are they most efficient) |
About changes in density. Most efficient in round/circular containers rather than shallow/tall ones. Currents occur above the heater. |
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What is condensation? What is evaporation? |
Gas particles slow down, forces pull them together, if it gets col enough liquids are formed. Particles escape a liquid, can happen below its boiling point. Occurs if: Particles are travelling in the right direction, have enough kinetic energy to overcome attractive forces. (Fastest particles are most likely to escape) This will decrease the liquid temperature. |
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When is rate of evaporation and rate of condensation faster? |
Evaporation : Temp higher, density lower, airflow greater, surface area larger. Condensation: Temp lower, density higher, airflow less, surface temperature lower |
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What affects heat energy transfer? |
Bigger surface area - more infrared waves can be emitted/absorbed by the surface. (Fins on vehicle engines, heat sinks - computer fans) Smaller volumes Type of material, conductor/insulator |
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How do vaccuum flasks keep heat in? |
Glass bottle double walled with a vacuum (stop conduction + convection) Walls were silvered (stop radiation) Supported with insulating foam (stop conduction) Stopper is plastic + filled w/ cork (stop conduction) |
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How are animals adapted to control heat? |
Hair on skin stand up + trap layer of air Too hot - blood flows to surface of the skin Animals in hot climates have larger ears |
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What properties do the most effective energy efficient methods have? |
Most effective methods give the biggest annual saving. Most cost effective methods are the cheapest (shortest payback time) |
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What are some methods of energy efficiency in the house? |
Cavity wall insulation - Foam squirted into brick gaps, there are pockets of air in the foam Loft insulation - Thick layer of fibreglass wool on the floor Draught proofing - Stips of foam + plastic around doors + windows Hot water tank jacket - lagging such as fibreglass wool Thick curtain - reduce conduction + radiation |
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What are U-values? |
Heat transfers faster with higher U-values W/m*mK |
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What is specific heat capacity? |
How much energy a substance can store, the amount of energy needed to raise the temperature of 1kg by 1 degree. E(j) = M(kg)*c(J/kg°C) *θ(°C) |
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How are electric storage heaters made? |
Have materials with high specific heat capacities (like water - can be pumped around pipes) Electric storage heaters store energy at nicht and release it in the day - heat is stored in concrete/bricks. Oil heaters have shc lower than water but higher boiling points (reach higher temp) |
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What are the different forms of energy? |
Electrical - Current flows Light - Sun, bulbs Sound - Noise Kinetic - Movement Nuclear - Nuclear reactions Thermal - Hot objects to cooler ones Gravitational potential - Anything which can fall Elastic potential - Stretch springs, elastic Chemical - Food, fuels |
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What is unique about energy? |
It can be transferred usefully from one form to another, stored or dissipated - never destroyed or created. It's only useful if its form can be converted. |
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Examples of energy transfers? |
Batteries : Chemical -> electrical + heat Electric generation : Kinetic -> electrical + heat Potential energy : Elastic potential -> kinetic + heat |
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What makes a device more efficient? Energy efficiency formula? Why is the energy wasted? |
If less energy is wasted (Useful energy/power out)/(Total energy/power in) It is dissipated and can't be easily used/collected back again |
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Comparing cost effectiveness of bulbs? |
Low energy bulbs are 4x as efficient as normal bulbs. They are more expensive but last longer (more cost effective) LED bulbs are more efficient and last even longer. But are more expensive and don't give out a lot of light. |
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Why would/wouldn't you replace old appliances? |
New efficient appliances are cheaper to run But they are expensive Work out payback time to see if it's cost effective |
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What is a heat exchanger? |
They pump a cold fluid through escaping heat, the temperature rises and the heat energy can be converted to a useful form. |
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Sankey diagram |
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What is a kilowatt hour? Forumlas for energy, units, and cost of running appliances? |
Amount of electrical energy used by a 1kw appliance for 1 hour. Depends on power and amount of time it's been left on for? Energy = power(kw) * time(h) Units = kw * hours cost = no. of units * price per unit |
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How do you read electricity meters? |
In Kwh, total energy used is subtract smaller reading from bigger one |
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Questions to ask when choosing an electrical appliance? Compare battery + clockwork radios |
Does one use less energy/is more cost effective? Are there practical differences? Both don't use mains. Clockwork is beter for the environment, free to power. Battery needs new batteries + is expensive |
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How are standards of living affected by electricity? |
Improve safety at night, refrigerators keep food fresh longer, keep vaccines cold. Without hospital machines patients would be poorer and could reduce life expectancy. Without internet/phones communication is also affected. |
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What are non renewable + renewable sources of energy? |
Non renewable - will run out, damage environment Coal, oil, natural gas, nuclear fuels Renewable - won't run out, don't do as much damage Wind, waves, tides, hydroelectric, soal, geothermal, food, biofuels. |
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How do power stations work? |
Fossil fuel burnt, chemical -> heat Heat water to make steam steam turns turbine, heat -> kinetic turbine is connected to generator, kinetic -> electric Nuclear stations use nuclear fission to make the heat |
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Method, advantages + disadvantages of wind power |
Windmills on moors/round coasts, each turbine has a generator which uses wind power. No pollution, no fuel costs, minimal running costs, no permanent damage to environment. High initial costs, spoil view, noisy, can't increase supply if wind stops. |
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Method, advantages + disadvantages of solar cells |
Generate currents from sunlight, useful in remote places (outback) and for road signs + satellites. No pollution, reliable in sunny countries, cost effective in Britain, energy is free, running costs low. High initial costs, too expensive to connect to National grid. |
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Method, advantages + disadvantages of hydroelectric energy |
Flooding of valley with a dam, rainwater is caught and allowed out through turbines. Provides immediate response for electricity demand, reliable, no fuel + minimal running costs. Big environmental impact, loss of habitat, reservoirs are unsightly when they dry up. |
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Method for Pumped storage |
Not a source of energy. Large power stations run at night (when demand is low) so extra electricity is generated. Spare energy pumps water up to a higher reservoir which can be released in peak demand. |
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Method, advantages + disadvantages of wave power |
Around the coast, waves provide an up + down motion to drive the generator. No pollution, no fuel costs, minimal running costs. Spoils the view, hazard to boats, fairly unreliable, high initial costs. |
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Method, advantages + disadvantages of tidal barrages |
Big dams with turbines, as the tide comes in the turbines are driven. No pollution, reliable, no fuel and minimal running costs. Prevents free access by boats, spoils view, alters habitat, if height is lower than expected less energy is made, initial costs are moderately high. |
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Method, advantages + disadvantages of geothermal energy |
Only possible in volcanic areas with hot rocks close to surface, steam rises to the surface to drive a generator. No environmental problems, sometimes doesn't need to be converted to electricity (heating buildings) Aren't many suitable areas, cost of building a power plant is high. |
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What are biofuels? How are they used? What are the advantages and disadvantages? |
Used in the same way as fossil fuels, can also be used in some cars. Come from organisms that are still alive/ dead organic matter. Sugar cane can ferment to make ethanol. Plant oils can produce biodiesel. Relatively quick + natural source of energy (carbon neutral) Large areas of forest have to be cleared, destroying habitats and releasing CO2. Limited by amount of farmland. |
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What are the problems with non renewable energy sources? |
Fossil fuels release CO2 which contributes to global warming. Burning coal + oil releases SO2 which causes acid rain. Coal mining makes the landscape a mess Oil spilling causes environmental problems Nuclear waste is dangerous and nuclear power is costly due to the cost of the power plant and decommissioning |
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What is carbon capture and storage? |
Reduces CO2 by collecting it before release, can be pumped into empty gas + oil fields. New ways of storing are being explored, storing CO2 dissolved in sea water at the bottom of the ocean, capturing with algae which can produce oil as a biofuel. |
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How do you compare different energy resources? |
Set up costs - Renewable is bigger Set up/decommissioning times - Gas is fastest to set up, nuclear is longest to decommision Reliability - Weather sources are unreliable Running/fuel costs - Renewable is lowest Environmental issues - If there's fuel (pollution), if there's weather (ugly) Location issues - power stations need to be near the stuff it runs on |
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What is the national grid? |
Energy from power stations to where it's needed in homes + industry. Power can be generated anywhere and supplied elsewhere on the grid. To transmit huge power you need high voltage/current, current uses lots of energy so more voltage is better. (400Kv) |
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What do transformers do? |
Step up transformer increase voltage, step down transformer reduces it to safe usable levels. |
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Benefits of overhead cables, underground cables. |
OH - low set-up cost, easy to access faults, easy set up, minimal land disturbance UG - minimal maintenance, hidden, not weather affected, reliable. |
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How can you deal with energy supply and demand? |
Supply can be increased with more power plants/increasing power output. Demand can be reduced by consumers using energy efficient appliances and not wasting energy. |
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What are the parts of a wave? |
Amplitude (volume), crests and falls Wavelength (pitch), length between point on one wave and point on the next wave Frequency - Number of wavelengths per second, Hz |
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What are the properties of transverse waves? What are the properties of longitudinal waves? |
TV - Vibrations perpendicular to the direction of energy transfer: light + em waves LT - Vibrations parallel to the direction of energy tansfer: sound + ultrasound waves |
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What is the formula for wave speed? |
Speed = Frequency(Hz)*Wavelength(m) |
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What are the properties of waves? |
All can be reflected, refracted and diffracted |
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How do you draw a ray diagram |
2 Lines Arrows on each line On the opposite side is dotted lines |
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What is reflection? |
Allows us to see things, when light reflects from an uneven surface light reflects at different angles, on an even surface it's reflected at the same angle for a clear reflection |
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What is refraction? |
Go through a new material and changes direction. If a wave meets a medium at an angle it changes direction (changes speed) |
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What is diffraction? |
Wave bends around obstacles, causing it to spread out. The narrower the gap/the longer the wavelength the more waves spread out. A gap the same size as the wavelength gives maximum diffraction. |
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What are electromagnetic waves? |
Radio, micro, infra, light, ultra, violet, x-ray, gamma They travel at the same speed, higher frequency = shorter wavelength |
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What are the properties of radio waves? |
10cm + wavelength. Long wave (1-10km) - diffracts around earth, receiver doesn't need to be in line of sight. Short wave (10-100m) reflected from ionosphere Shorter wave (10cm-10m) must be in sight of transmitter, TV + FM radio |
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What are the properties of microwaves? |
To and from satellites, passes easily through the atmosphere. Satellite TV - Signal transmitted to satellite receiver dish, transmits back in a different direction to be received by dish on ground. Mobile phone - some wavelengths are absorbed by water which heats it up (could be dangerous if it's your head) Remote sensing satellites - monitor oil spills, track iceberg movements |
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What are the properties of infrared waves? |
In remote controls - emit different patterns of infrared waves to send different commands. Optical fibres - send data over long distances, both infrared and light waves. Signal is carried as pulses of light/infrared radiation off the side of a narrow core. |
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What are the properties of visible light? |
In cameras - a lens focuses visible light onto a light sensitive film, by varying the aperture and shutter speed a photographer can change the amount of light. |
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What are the properties of sound waves? |
If it reaches the eardrum you can hear it. The more particles the faster it travels. They are reflected by hard flat surfaces (echo), there is a delay between the original sound and the echo as it has to travel faster. Also refract. |
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What is red shift? |
Elements absorb different light frequencies producing a specific pattern of dark lines, looking at light from galaxies the frequencies are slightly lower (red shift) More distant galaxies have greater red shifts |
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What is the doppler effect? |
Moving towards you, high frequency + shorter wavelength (compression). Away, lower frequency + longer wavelength |
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What is the big bang theory? Steady state theory? |
Everything was a single point and then it expanded which is still going on. We can use this current rate to estimate its age - 14 billion. Discovery of cosmic microwave background radiation helped this theory. Universe has always been the same, says the expansion is matter being created. |
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What is uniform microwave radiation? |
Low frequency electromagnetic radiation has been detected everywhere in the universe, cosmic background radiation which the big bang explains. When the universe was extremely hot it emitted high frequency radiation as the universe expanded it cooled and dropped in frequency. |
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Limitations of the big bang theory? |
It predicts the expansion slowing down, but it's speeding up Doesn't explain what caused the bang But it explains so much we can't throw it away. |
