Topic 1 – Energy

• System


  An object or group of objects where energy transfer takes places
• Closed System


  Nothing can enter/escape (net energy change is always zero)
• Types of Energy


  • Chemical
  • Electrostatic
  • Thermal
  • Elastic potential
  • Magnetic
  • Nuclear
  • Kinetic (K.E)
  • Gravitational potential (G.P.E)
• How energy is transferred (between different stores)

  1. Electrically

  2. Heating

  3. Radiation – sound/light

  4. Mechanically or doing WORK - (energy transfer due to a FORCE)
• Mechanical energy transfers


  • A person throwing a ball upwards
  • Ball falling down
  • A car slowing down by braking
  • A car slowing down by crashing into an object
• Initial store


  • Chemical (human)
  • G.P.E (ball)
  • K.E (car)
  • K.E (car)
• Force


  • The force of the arm
  • Gravity
  • Friction
  • Contact force (object)
• Final store


  • G.P.E (ball)
  • K.E (ball)
  • Thermal (brakes)
  • Thermal, Elastic
• Specific Heat Capacity (SHC)

  • The energy needed to raise the Temperature of 1kg of a substance by 1°C
  • High SHC means lots of energy absorbed (or can be released)
• Investigating SHC of a material


  1. Measure mass of material

  2. Wrap material in insulating layer

  3. Makes 2 hole - Insert thermometer and heater

  4. Measure initial temperature

  5. Set voltage (e.g. 10V) on power supply

  6. Record temperature and current at regular time intervals

  7. After 10 readings turn off supply and calculate power for each reading (P=VI)

  8. Calculate energy transferred for each time interval using (E=Pt)

  9. Plot a graph of temperature against energy

  10. Calculate SHC (1 / gradient x mass)
• Energy can't be created/destroyed only transferred
• During energy transfer, some is dissipated into useless stores (heat, sound)
• Power


  • Measured in W (Watts) -> (1W = 1J/s)
  • Power is the RATE of energy transfer – how QUICKLY energy transferred
  • More power = Transfers energy FASTER (more joules per second)
  • More power also means loses energy quicker
• Conduction


  • Particles gain energy
  • Increase in K.E
  • Collide with neighbouring particles
  • Pass on their K.E
  • Thermal conductivity – how much heat energy allowed to pass an object
• Convection


  • Gas particles gain energy
  • Move faster
  • Particles move apart
  • Gas becomes less dense and rises
  • Displaces cooler gas at the top
• Lubrication


  • Reduces friction between moving parts
• Streamlining


  • Reduces collisions with air particles
• Insulation in the house

  1. Cavity Wall: Air gap between walls. Reduces heat loss by conduction

  2. Cavity Wall Insulation: Fill the gap with foam. Reduces heat loss by convection

  3. Loft Insulation: Reduces heat loss by convection

  4. Double glazed windows: Air gap. Reduces loss by conduction

  5. Draught excluders: Around doors and windows. Reduce convection
• Conservation of Energy


  • P = W/T
  • P = E/T
• Renewable energy sources


  • Solar
  • Wind
  • Water (Wave power)
  • Water (Tidal barrage)
  • Hydro-electricity
  • Bio-fuel
  • Geothermal
• Non-renewable energy sources


  • Fossil fuels (Oil, Natural Gas, Coal)
  • Nuclear (Uranium, Plutonium)
• Renewable energy: Solar cells / Wind power turbines


  • Pros: Renewable, No pollution (except manufacture), Low running costs

  Cons: Visual and Noise pollution (wind), Need lots of them for significant energy, Wind and Sun are unpredictable, Unable to increase during high demand, Expensive to build
• Geothermal energy


  Water is heated by hot rocks/radioactive decay core of earth and turns into steam, which turns a turbine and generator.

  Thermal -> K.E -> ELECTRIC

  Pros: Renewable, No pollution, Always available (reliable)

  Cons: Expensive to build, Not many suitable locations
• Hydro-electric power


  Water from high valley flows down and turns a turbine and generator.

  G.P.E -> K.E -> ELECTRIC

  Pros: Renewable, Can meet immediate demand, Low running costs

  Cons: Damages habitats, High initial cost, Clearing land releases C02
• Bio-fuel


  Made from plant and animal waste

  Pros: Carbon neutral, Reliable

  Cons: Increased food prices, Forest cleared
• Non-renewable energy: Fossil fuels / Nuclear power

  Pros: Energy on demand, Can Increase energy supply, Reliable (not weather based), Nuclear: No dangerous gases

  Cons: Both: Finite, Nuclear -> Radiation (danger), Nuclear -> Decommission time, Fossil -> release CO2 / SO2
• Efficiency can be increased by: lubrication/Insulation/Streamlining
• Reduces friction, so less energy wasted thermally