AQA GCSE Physics 1a2 Using Energy

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AQA GCSE Physics 1a-2Using Energy

• GCSE Physics pages 38 to 49

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AQA GCSE Specification

• ENERGY EFFICIENCY
• 11.2 What is meant by the efficient use of
  energy?
• Using skills, knowledge and understanding of how
  science works
• to describe the intended energy
  transfers/transformations and the main energy
  wastages that occur with a range of devices
• to calculate the efficiency of a device using
• efficiency useful energy transferred by the
  device / total energy supplied to the device
• to evaluate the effectiveness and cost
  effectiveness of methods used to reduce energy
  consumption.
• Skills, knowledge and understanding of how
  science works set in the context of
• Energy cannot be created or destroyed. It can
  only be transformed from one form to another
  form.
• When energy is transferred and/or transformed
  only part of it may be usefully
  transferred/transformed.
• Energy which is not transferred/transformed in
  a useful way is wasted.
• Both wasted energy and the energy which is
  usefully transferred/transformed are eventually
  transferred to their surroundings which become
  warmer.
• Energy becomes increasingly spread out and
  becomes increasingly more difficult to use for
  further energy transformations.
• The greater the percentage of the energy that
  is usefully transformed in a device, the more
  efficient the device is.

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Forms of energyNotes questions from pages 38 39

• Copy the list of different forms of energy on
  page 38.
• Copy and answer questions (a), (b), (c) and (d)
  on pages 38 and 39.
• Copy the Key Points on page 39.
• Answer the summary questions on page 39.

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Forms of energy ANSWERS

• In text questions
• Electrical energy.
• High speed train (Train de grand vitesse)
• It is lost to the surroundings through heat
  transfer.
• From gravitational potential energy.

• Summary questions
• (a) Gravitational potential, kinetic
• (b) Electrical, thermal
• 2. (a) For example a candle and a torch.
• A candle transfers chemical energy to light
  and heat. a torch transfers chemical to
  electrical and then light and heat.
• (b) (i) A torch is usually more convenient.
• (ii) This is a matter of opinion.
• 3. Mechanical energy is transformed to
  gravitational potential energy as the pile driver
  lifts the heavy steel block. As the steel block
  falls, the gravitational potential energy is
  transformed into kinetic energy of the block.
  When the block hits the ground the kinetic energy
  is transformed into heat and sound energy.

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Conservation of energyNotes questions from pages
40 41

• What is meant by the conservation of energy?
• Explain how energy is conserved in (a) the
  oscillation of a pendulum and (b) a bungee jump.
• Copy and answer questions (a), (b) and (c) on
  pages 40 and 41.
• Copy the Key Points on page 41.
• Answer the summary questions on page 41.

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Conservation of energy ANSWERS

• In text questions
• (a) (i) Kinetic energy changes to thermal energy
  in the brakes and thermal energy of the
  surroundings.
• (ii) Kinetic energy changes to gravitational
  potential energy as it climbs the hill. The
  gravitational potential energy changes back to
  kinetic energy as it descends. Thermal energy of
  the surroundings due to air resistance and
  friction is produced throughout.
• (b) It is transformed by air resistance to
  thermal energy of the surroundings.
• (c) Start ? GPE ? KE Heat energy ? Strain
  energy Heat energy ? GPE? KE Heat energy ?
  etc

• Summary questions
• 1. (a) Gravitational potential, electrical,
  thermal, gravitational potential.
• 2. (a) On descent Gravitational potential energy
  ? kinetic energy thermal energy due to air
  resistance.
• On impact Kinetic energy ? elastic energy of
  trampoline thermal energy due to impact
  sound.
• On ascent Elastic energy of trampoline ?
  kinetic energy ? gravitational potential energy
  thermal energy due to air resistance.
• (b) The ball has less energy at the top of
  its bounce than at the point of release.
• (c) (i) Type of trampoline (ii) Categoric
• 3. Elastic energy of the rubber straps is
  transformed into kinetic energy of the capsule.
  The kinetic energy is transformed into
  gravitational potential energy as the capsule
  rises to the top of its flight, etc. as in bungee
  jumper.

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Useful energyNotes questions from pages 42 43

• Give two examples each of (a) useful energy and
  (b) wasted energy.
• What effect, energy wise, does the force of
  friction have in machines?
• Copy out the paragraph under the heading
  Spreading out on page 43.
• Copy and answer questions (a), (b) and (c) on
  pages 42 and 43.
• Copy the Key Points on page 43.
• Answer the summary questions on page 43.

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Useful energy ANSWERS

• In text questions
• It is gained by the surroundings as thermal
  energy.
• It is transferred to the surroundings as thermal
  energy by friction between its moving parts and
  in the brakes, and by air resistance.
• The hot water mixes with the cold water. Its
  thermal energy spreads out and cant be used
  again.

• Summary questions
• 1. (a) useful thermal energy of the element
• wasted thermal energy of the case
• (b) useful light and sound energy
• wasted thermal energy
• (c) useful thermal energy of the water
• wasted thermal energy of the steam and
  of
• the kettle itself
• (d) useful sound energy
• wasted thermal energy in the wire
• 2. (a) It would heat up . The lubricating oil and
  the gears would get hot.
• (b) The feet would get too hot and sweaty.
• (c) The drill would heat up and smoke if it
  burns the wood.
• 3. Air resistance causes friction as the pendulum
  swings. This produces heat and so the pendulum
  loses energy to the surroundings and stops.

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Energy and efficiencyNotes questions from pages
44 45

• Explain how energy in joules is related to weight
  and height.
• What is a Sankey diagram? Draw an example.
• Copy the equation defining efficiency on page
  44.
• Calculate the efficiency of a light bulb if it
  supplies 16J of light when supplied with 80J of
  electrical energy.
• Copy out the table headed Improving efficiency
  on page 45.
• Copy and answer questions (a), (b), (c) and (d)
  on pages 44 and 45.
• Copy the Key Points on page 45.
• Answer the summary questions on page 45.

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Energy and efficiency ANSWERS

• In text questions
• You use your muscles, so the gravitational
  potential energy is transformed in them to
  thermal energy.
• 85 J
• It is transformed to heat energy in the lamp
  holder and the surroundings
• 4

• Summary questions
• (a) Supplied to.
• (b) Wasted by.
• (c) Supplied to, wasted by.
• (a) 36 J
• (b) 0.40 (or 40)
• 3. 800 J

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Energy and efficiency issues Notes questions
from pages 46 47

• Answer questions 1 and 2 on page 47.

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Energy and efficiency issues ANSWERS

• 1. (a) It uses less fuel per kilometre.
• (b) Electric cars cant go very far without
  being recharged.
• 2. (a) The hybrid car.
• (b) 10.20

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How Science Works ANSWERS

• Correctly labelled graph with height on the
  Y-axis and temperature on the X-axis. The line of
  best fit should be a CURVE.
• 1 mm
• Rapid initial increase in bounce height. Rate of
  increase decreases at higher temperatures.
• Prediction correct in the range 3oC to 51oC. But
  overall it is not fully supported.
• Yes. Points are not exactly on the line of best
  fit. Also final result is lower than previous
  one.
• Yes. All but one of the results appear to be 3cm
  below those of the manufacturer.
• The bounce height of the ball will increase
  whilst the ball is warming up.