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					               Question
• What electromagnetic waves carry heat?




                Energy and Electricity
              Answer
• Infra-red




              Energy and Electricity
                Question
• What is a transfer of energy?




                 Energy and Electricity
                Answer
• Energy changing from one type to another,
  chemical to heat.




                Energy and Electricity
                Question
• How can we try to stop a tank of hot water
  from cooling down?




                 Energy and Electricity
                Answer
• Add insulation and / or a vacuum around
  it.




                 Energy and Electricity
               Question
• What are the ways heat is transferred?




                 Energy and Electricity
                Answer
• Conduction, convection and radiation.




                 Energy and Electricity
                Question
• Do all bodies (objects) emit thermal
  radiation?




                 Energy and Electricity
                 Answer
• Yes they do!




                 Energy and Electricity
                Question
• Do all bodies absorb thermal radiation?




                 Energy and Electricity
                 Answer
• Yes they do!




                 Energy and Electricity
                Question
• Which will emit more radiation, a block of
  wood at 29oC or some steel at 25oC?




                  Energy and Electricity
                 Answer
• The wood, because it is at a higher
  temperature.




                 Energy and Electricity
                Question
• Is a dark surface a good or poor emitter of
  radiation?




                  Energy and Electricity
                Answer
• A good emitter.




                    Energy and Electricity
               Question
• Is a dark surface a good or poor absorber
  of radiation?




                 Energy and Electricity
                Answer
• A good absorber.




                Energy and Electricity
                 Question
• Is a light surface a good or poor emitter of
  radiation?




                  Energy and Electricity
                    Answer
• A poor emitter.




                    Energy and Electricity
                Question
• Is a light surface a good or poor absorber
  of radiation?




                 Energy and Electricity
                Answer
• A poor absorber.




                Energy and Electricity
                Question
• For conduction to take place particles
  must be still, true or false?




                 Energy and Electricity
               Answer
• False, the more movement the more
  energy they transfer.




                Energy and Electricity
                Question
• For convection to take place particles must
  be moving, true or false?




                 Energy and Electricity
                 Answer
• True, the particles carry the heat as they
  move.




                  Energy and Electricity
                Question
• Conduction takes place in solids. True or
  false?




                 Energy and Electricity
          Answer
• True.




          Energy and Electricity
                Question
• Convection takes place in liquids only, true
  or false?




                  Energy and Electricity
                Answer
• False. Liquids and gases are able to move
  and transfer heat.




                 Energy and Electricity
                Question
• Conduction in metals is good because
  they have electrons that are able to do
  what?




                 Energy and Electricity
                Answer
• Move through the metal.




                Energy and Electricity
                Question
• In convection, what causes ‘heat’ to rise?




                 Energy and Electricity
                Answer
• The particles move more, become less
  dense and rise upwards.




                Energy and Electricity
               Question
• Why are room heaters large and flat?




                 Energy and Electricity
                 Answer
• A large surface can give out more heat.




                 Energy and Electricity
               Question
• Why is wood not as good a conductor as
  steel?




                Energy and Electricity
                 Answer
• Metal is different to wood. So they behave
  differently. The metals have electrons that
  can conduct heat well. Wood does not.




                  Energy and Electricity
                Question
• Which will cool faster and why?

• A steel block at 35oC in a 25oC room, or a
  wood block at 10oC in a freezer at -10oC?




                 Energy and Electricity
               Answer
• The wood block would cool quicker
  because there is a 20oC difference
  between the temperatures compared to a
  10oC difference for the steel block.




                Energy and Electricity
                Question
• What is the energy transfer in an electric
  oven?




                  Energy and Electricity
                  Answer
• Electricity goes to heat.




                  Energy and Electricity
                Question
• What is the energy transfer in a car. Petrol
  is used to provide energy to move?




                  Energy and Electricity
                 Answer
• Chemical (petrol) to kinetic (movement)




                 Energy and Electricity
                Question
• What is the energy transfer in a wind
  turbine?




                 Energy and Electricity
                 Answer
• Kinetic (movement) to electrical.




                  Energy and Electricity
                Question
• What is the energy transfer in a light bulb?




                  Energy and Electricity
                   Answer
• Electrical to light.




                    Energy and Electricity
                Question
• What is the waste energy transfer in a light
  bulb?




                  Energy and Electricity
                Answer
• Heat produced is wasted.




                Energy and Electricity
                Question
• What is the waste energy transfer in a
  car?




                 Energy and Electricity
                Answer
• Heat is wasted.




                    Energy and Electricity
                 Question
• The equation for efficiency is:-
• Efficiency = useful energy transferred
                 total energy supplied
Calculate the efficiency of a fan using 100J
 but 55J are wasted as heat.



                  Energy and Electricity
                Answer
• 45/100 = 0.45 or 45%




                Energy and Electricity
                Question
• Which is more cost effective, double
  glazing costing £2000 and saving 100J of
  energy, or loft insulation costing £500 and
  saving 140J of energy?




                  Energy and Electricity
                     Answer
• Loft insulation.




                     Energy and Electricity
                Question
• The law of conservation of energy states
  that it cannot be created or destroyed. So
  if 100J of chemical energy is burnt and
  35J are used to move a car, 5J are
  converted to sound, how much is possibly
  turned into heat?



                 Energy and Electricity
        Answer
• 60J




        Energy and Electricity
                Question
• The law of conservation of energy states
  that it cannot be created or destroyed. If
  10J of energy lands on a microphone as
  sound, 9.8J goes to the loudspeaker, how
  much is lost?




                 Energy and Electricity
                 Answer
• 0J, energy cannot be lost, but 0.2J are
  transferred as waste heat energy.




                 Energy and Electricity
               Question
• What form of energy does waste energy
  eventually become?




                Energy and Electricity
          Answer
• Heat.




          Energy and Electricity
                 Question
• As energy is used in several
  transformations, it gets spread out. Does
  this make it easier or more difficult to use
  again?




                  Energy and Electricity
                    Answer
• More difficult.




                    Energy and Electricity
                Question
• A device that uses 25J out of 50J is less
  efficient than one that uses 33J out of 99J,
  true or false?




                  Energy and Electricity
                 Answer
• False, 25/50 = 0.5 but 33/99 = 0.33.




                 Energy and Electricity
               Question
• Why do we not have many electric cars?




                Energy and Electricity
                Answer
• They have a small range.




                Energy and Electricity
                Question
• What is the energy transfer when a roller
  skater speeds up down a hill?




                 Energy and Electricity
                  Answer
• Gravitational potential energy to kinetic
  energy.




                  Energy and Electricity
                 Question
• In an electric kettle, what is the useful
  energy transfer?




                   Energy and Electricity
                  Answer
• Electrical to thermal.




                  Energy and Electricity
                Question
• Why are kettles often white or shiny?




                 Energy and Electricity
                 Answer
• They are poor emitters of radiation.




                  Energy and Electricity
                Question
• What colour warm up quicker if left in the
  sun?




                  Energy and Electricity
                    Answer
• A black object.




                    Energy and Electricity
               Question
• Why are solar panels black?




                Energy and Electricity
                Answer
• They absorb radiation much better than
  light ones.




                 Energy and Electricity
                Question
• The equation for energy transferred is:-
• energy transferred = power X time
(kilowatt-hour kWh) (kilowatt, kW) (hour, h)
How much energy is transferred in 30
  minutes when the power is 1000W?




                 Energy and Electricity
                Answer
• 1000W = 1kW
• 30 min = 0.5 hours

• So 1 x 0.5 = 0.5kWh




                 Energy and Electricity
                 Question
• The cost of electricity is number of
  kilowatt-hours x cost per kilowatt. So if a
  fire is on and uses 3kWh, and the cost is
  11p per kWh, what is the total cost?




                  Energy and Electricity
         Answer
• 33p.




         Energy and Electricity
                 Question
• A 2kW kettle is used for 30 minutes each
  day on average. If the cost of electricity is
  11p per unit (1kWh = 1 unit), what is the
  cost?




                   Energy and Electricity
                Answer
• 2kWh x 0.5 hours x 11p = 11p




                Energy and Electricity
               Question
• What are the units of power?




                 Energy and Electricity
                  Answer
• Watt or kilowatt.




                  Energy and Electricity
                Question
• What is the unit of energy?




                 Energy and Electricity
                    Answer
• The Joule, (J).




                    Energy and Electricity
                Question
• How is electricity transferred from the
  power station to a home?




                  Energy and Electricity
                  Answer
• By the national grid.




                  Energy and Electricity
                Question
• Does electricity from a power station go
  through a step up or step down
  transformer before the national grid?




                 Energy and Electricity
            Answer
• Step up




            Energy and Electricity
                Question
• Does electricity from the national grid go
  through a step up or step down
  transformer before a house?




                  Energy and Electricity
               Answer
• Step down.




               Energy and Electricity
                Question
• Why is a high voltage (potential difference)
  used in the national grid?




                  Energy and Electricity
                 Answer
• It reduces current loss, so less energy is
  wasted.




                  Energy and Electricity
               Question
• Why is coal not a good energy source in
  power stations?




                 Energy and Electricity
                  Answer
• It produces a lot of pollution such as acid
  rain.




                  Energy and Electricity
                Question
• Why is a gas turbine power station useful?




                 Energy and Electricity
                 Answer
• It can be turned on quickly to produce hot
  gases, coal and oil have to heat up water
  to produce steam.




                 Energy and Electricity
                Question
• A nuclear power station is slow to start up,
  true or false?




                  Energy and Electricity
          Answer
• True.




          Energy and Electricity
               Question
• Nuclear power stations do not produce
  greenhouse gases, true or false?




                Energy and Electricity
                Answer
• True. This makes them less polluting than
  power stations that burn fossil fuels.




                 Energy and Electricity
               Question
• What must steam turn to make electricity
  in most power stations?




                 Energy and Electricity
                 Answer
• A generator.




                 Energy and Electricity
                 Question
• Renewable energy sources such as
  waves, hydroelectric and tidal energy can
  turn turbines to produce electricity, true or
  false?




                   Energy and Electricity
          Answer
• True.




          Energy and Electricity
               Question
• What causes a solar cell to produce
  electricity?




                 Energy and Electricity
                 Answer
• Radiation from the sun.




                 Energy and Electricity
              Question
• Name 3 types of renewable energy
  source.




                Energy and Electricity
                    Answer
•   Solar
•   Wind
•   Hydroelectric
•   Tidal
•   Wave
•   Geothermal


                    Energy and Electricity
               Question
• What is geothermal energy?




                Energy and Electricity
               Answer
• Energy from hot water pumped down into
  hot rocks and recovered.




                Energy and Electricity
                Question
• Name a type of pollution associated with a
  wind turbine.




                 Energy and Electricity
                 Answer
• Noise or visual.




                     Energy and Electricity
               Question
• Why might a tidal barrage used to produce
  electricity by renewable energy be bad for
  the environment?




                 Energy and Electricity
                  Answer
• It will destroy the habitat of animals and
  plants as water gets trapped behind a
  barrier.




                  Energy and Electricity
                Question
• Which type of power station is very
  expensive to build?




                 Energy and Electricity
             Answer
• Nuclear.




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posted:4/9/2010
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