Energy

Cards (48)

  • In the UK a mix of energy supplies are used so should one supply become unavailable, others can be used without disruption to supplies.
  • Some energy sources are more reliable than others. Coal, oil, gas and nuclear are reliable sources as they can supply a continuous flow of electricity.
  • Electricity from wind turbines relies on the wind blowing, solar power does not work at night and hydro-electric requires a continuous supply of water. These are considered unreliable sources.
  • The total amount of energy used in the world is increasing as the population increases and each person is using more energy.
  • Renewable energies only make up around 20% of total energy consumption and this trend is unlikely to change until after 2035.
  • Future world agreements on emissions are likely to determine the trend of using fossil fuels.
  • As reserves of coal, oil and gas dwindle, an increase in the use of renewable energies is likely.
  • what are the different energy stores?
    Thermal,
    kinetic,
    gravitational potential,
    elastic potential,
    chemical,
    magnetic,
    electrostatic,
    nuclear
  • What is a closed system?
    A system where neither matter nor energy can enter or leave
  • Kinetic energy store
    Anything that's moving has energy in its kinetic energy store. Energy is transferred to this store when an object speeds up and is transferred away from this store when an object slows down.
  • What is the formula for kinetic energy?

    Ek=1/2m(kg)v^2(m/s)^2
  • What is the formula for gravitational potential energy?
    Ep=m(kg) g(n/kg) h(m)
  • what happens to a falling object when there's no air resistance?
    Energy lost from G.P.E store is equal to energy gained in kinetic energy store
  • what is the formula for elastic potential energy?
    Ee=1/2 x spring constant(N/M) x extension^2(m)
  • What is specific heat capacity?
    The amount of energy required to increase the temperature of 1kg of a substance by 1oC
  • What is the formula for heat capacity?
    ΔE(change in thermal energy)=M(mass in kg)C(specific heat capacity j/kgoC)Δθ(temperature changeoC)
  • How can we investigate specific heat capacity?
    1)To investigate a solid material, you'll need a block of the material with two holes in it
    2)measure the mass of the block and wrap an insulating material around it to reduce the energy transferred from the materials to the surroundings. insert thermometer and a heater
    3)Measure the initial temperature of the block and set the potential difference of the power supply to be 10v. turn the power supply and start a stop watch
    4)When you turn on the power the current in the circuit does work on the heater, transferring energy electrically from the power supply to the heater thermal energy store.
    5)As the block heats up, take the readings of the temperature and current every minute for 10min. you should find that the current through the circuit doesn't change as the block heats up
    6)When you've collected enough readings , turn off the power supply using your measurement of the current and potential difference of the power supply you can calculate the power supplied to the heater using p=vi
    7)You can repeat this experiment with different materials to see how their heat capacity compares e.g for a liquid just placed to the heater and thermometer in an insulated beaker filled with a known mass of the liquid.
  • What is power?
    the rate at which energy is transferred
  • What is power measured in?
    Watts. One watt =1 joule of energy transferred per second
  • What are the formulas for power?
    P=E/T(Energy transferred/Time)
    P=W/T(Work done/Time)
  • Conduction
    Conduction occurs mainly in solids. Conduction is the process where vibrating particles transfer energy to neighbouring particles.
  • What is conduction?
    The particles in the part of the object being heated vibrate more and collide with each other. These collisions cause energy to be transferred between particles kinetic stores. This process continues throughout the object until the energy is transferred to the thermal energy store of the surroundings. Thermal conductivity is a measure of how quickly energy is transferred through a material in this way. Materials with high thermal conductivity transfer energy between their particles quickly.
  • Convection
    Convection only occurs in liquids and gases. Convection is where energetic particles move away from hotter to cooler regions. Unlike in solids, the particles in liquids and gases are able to move. When you heat a region of a gas or liquid, the particles move faster and the space between the individual particles increases. This causes the density of the region being heated to decrease. Bc liquids and gases can flow, the warmer and less dense region will rise above denser and cooler regions . If there is a constant heat source a convection current can be created.
  • How do radiators create convection currents?
    1.energy is transferred from the radiator to nearby air particles by conduction.
    2.air by the radiator becomes warmer and less dense so it vibrates more and collide more frequently
    3.warm air rises and is replaced by cooler air which is then heated by radiator
    4.the previous warm air cools becoming denser so it sinks down creating a cycle of the flow of air
    5.The cycle repeats causing a flow of air to circulate around the room-this is a convection current.
  • How does lubrication reduce frictional forces?
    For objects that are rubbed together , lubricants can be used to reduce the friction between the objects surfaces when they move . Lubricants are usually liquids, so they can flow easily between objects and coat them.
  • How does insulation reduce the rate of energy transfer by heating ?
    Have thick walls made by materials with low thermal conductivity, the thicker the walls the lower the thermal conductivity the slower the rate of energy transfer will be.
  • What are some examples of thermal insulation?
    Cavity walls, made up of an inner and outer walls, with an air gap in the middle. The air gap reduces the amount of energy transferred by conduction through the walls.
    loft insulation, can reduce convection currents being created in lofts.
    double glazed windows they have an air gap between two sheets of glass to prevent energy transfer by conduction through the windows
    draught excluders around doors an windows reduce energy transfers by convection.
  • How to investigate the effectiveness of materials as thermal insulators?
    1)Boil water in a kettle. Pour some of the water into a sealable container. to a safe level then measure the mass of the liquid in the container.
    2)Use a thermometer to measure the initial temperature of the water
    3)Seal the container and leave it for 5 minutes . Measure this time using a stop watch.
    4) Remove the lid and measure the final temperature of the water
    5)Pour away the water and allow the container to cool to room temperature.
    6)Repeat this experiment, BUT WRAP THE CONTAINER IN A DIFFERENT MATERIAL once it has been sealed make sure you use the SAME MASS OF THE WATER AT THE SAME INITIAL TEMP each time.
    7)The lower the temperature difference the better that material is as a thermal insulator . Materials like bubble wrap cotton wool are good thermal insulators
  • How can the efficiency of energy transfers be improved?
    By insulating objects, lubricating them or making the more streamlined.
  • What is the formula for efficiency?
    Useful energy output Transfer/ total energy input Transfer
  • What is the formula for efficiency?
    Useful power output / total power input
  • Why is useful energy output not usually equal to total energy input?
    No device is 100% efficient and wasted energy is usually transferred to useless thermal energy stores. An exception of this is electric heaters they are usually 100% efficient because all the energy in the electrostatic energy store is transferred to useful thermal energy stores. Ultimately all the energy ends up being transferred to thermal energy stores.
  • What are non-renewable energy resources?
    -Coal
    -Oil
    -Natural Gas
    -Nuclear fuels
    resources that will end soon
  • What are renewable energy resources?
    solar, wind, water waves, hydro-electricity, bio-fuel, tides, geothermal. They are energy resources that will never run out, as they can be "renewed" as they are used.
  • Explain wind power as a renewable resource?
    This involves putting lots of wind turbines up in exposed places like on moors or round coasts. Each turbine has a generator inside it rotating blades turn the generator and produce electrically. There's no pollution however downsides are that they do spoil the view and you need about 1500 wind turbines to replace one-coal-fired power station. They can also be very noisy affecting people who live nearby. There is also the problem of wind turbines stopping when the wind stops or if the wind is too strong and its impossible to increase supply when there is extra demand. On average wind turbines produce electricity 70-85%. The initial costs are quite high , but there are no fuel costs and minimal running costs. There is no permanent damage to the landscape-if you remove the turbines , you remove the noise and the view returns to normal.
  • Explain solar cells as a renewable resource?
    They generate electric currents directly from sunlight .Solar cells are often the best source of energy to charge batteries/ calcs which don't use much electricity. It is often used in remote places where there's not much choice and to power road signs and satellite's. There's no pollution . In sunny countries its a very reliable resource but only during the daytime but they can still be effective in cloudy countries like Britain. But you cant increase the power output when there's extra demand. So there used on a small scale .
  • Explain Geothermal energy as a renewable resource?

    This is possible in volcanic areas or where hot rocks lie quite near to the surface . The source of much of the energy is slow decay or various radioactive elements including uranium deep inside the earth. This is brilliant free energy that's reliable and does very little damage to the environment.. Geothermal energy can be used to generate electricity or heat buildings directly. However drawbacks are that there aren't many suitable locations for power plants and that the cost of building a power plant is often high compared to the amount of energy it produces.
  • Explain hydro-electricity as a renewable resource?
    Usually requires the flooding of a valley by building a big dam. Water is allowed out through turbines. There is no pollution, but there is an impact on the environment and possible loss of habitat for some species. The reservoirs can also look very unsightly when they dry up , so putting them in remote valleys tends to reduce their impact on humans. An advantage is it can provide immediate response to an increased demand for electricity . There's no problems with reliability except when there's a drought. Initial costs are high but there are no fuel costs and minimal running costs.
  • Explain wave power as a renewable resource?
    You need lots of small wave-powered turbines located around the moving turbines are connected to a generator . No pollution the main problems are disturbing the sea bed and the habitats of marine animals , spoiling the view and being a hazard to boats. They are fairly unreliable since waves die out when the wind drops. Initial costs are high but there are no fuel costs and minimal running costs. not useful on large scale only on small islands.
  • Explain tidal barrages renewable resource?
    They are big dams built across river estuaries, with turbines in them as the tide comes in it fills up the estuary the water is then allowed through the turbines at a controlled speed. The tides are produced by the gravitational pull of the sun and moon. There is no pollution . The main problems are preventing free access by boats, spoiling the view and altering the habitat of wildlife. The tides are pretty reliable in the sense that they happen twice a day without fail and always near to the predicted height . The only drawback is that the height of the tide is variable so lower tides will provide significantly less energy than the bigger spring tides they also don't work when they water level is the same each side of the barrack this happens 4 times a day because of the tides. Initial costs are moderately high but there are no fuel costs and minimal running costs. It can only be used in the most suitable estuaries.