Topic 1: Energy

• Energy cannot be created or destroyed, only transferred usefully, stored or dissipated
• Stretching a spring

  1. Force applied to change the length of the spring

  2. Doing work on the spring
• Elastic potential energy

  Energy stored in a stretched spring
• Extension of a spring

  Directly proportional to the force applied, provided the limit of proportionality is not exceeded
• If too much force is applied, the extension is no longer directly proportional to the force applied and the limit of proportionality is exceeded
• After the limit of proportionality, the spring is inelastically deformed, so it will not return back to its original shape and may break
• Gravitational potential energy

  Energy stored in an object due to its position above the Earth's surface due to the force of gravity acting on it
• Thermal energy

  Energy stored due to an object's temperature
• Specific heat capacity

  The amount of energy required to raise the temperature of 1kg of a substance by 1 degrees celsius
• System

  An object or a group of objects
• In a closed system, no energy can enter or leave
• Pendulum motion

  1. At the top: maximum gravitational potential energy

  2. Swinging downwards: gravitational potential energy transferred to kinetic energy

  3. At the bottom: maximum kinetic energy

  4. Swinging upwards: kinetic energy transferred to gravitational potential energy
• Friction causes energy to be transferred to thermal energy (less useful energy is wasted)
• There is friction in the fixed point of the pendulum and there is also friction as the pendulum passes through the air particles, which will cause the pendulum to gradually swing with less energy and eventually stop
• Reducing friction

  Reduces unwanted energy transfers
• Bungee jump

  1. At start: all energy is gravitational potential energy

  2. Falling: gravitational potential energy transferred to kinetic energy

  3. Rope tightening: maximum kinetic energy

  4. Rope fully extended: maximum elastic potential energy

  5. Ascent: kinetic energy transferred back to gravitational potential energy

  6. Top of ascent: maximum gravitational potential energy

  7. Never returns to original position: energy dissipated as thermal energy due to friction and non-elastic stretching
• Work

  Whenever energy is transferred from one store to another
• Types of work

  • Mechanical work (using force to move an object)
  • Electrical work (current transferring energy)
• Power

  The rate at which energy is transferred or the rate at which work is done
• Efficiency

  Can be increased by reducing waste output and recycling waste output
• Thermal conductivity

  The rate of energy transfer by conduction across a material
• The higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across that material
• Reducing thermal energy transfer from a house

  1. Use materials with low thermal conductivity

  2. Construct thick walls

  3. Use two layers with cavity insulation

  4. Use double glazed windows

  5. Use loft insulation
• Main fossil fuels

  • Coal
  • Oil
  • Gas
• Advantages of fossil fuels

  • Reliable
  • Release a great amount of energy
  • Abundant and relatively cheap
  • Extremely versatile
• Disadvantages of fossil fuels

  • Release a huge amount of carbon dioxide
  • Non-renewable
  • Burning can release other pollutants
• Burning diesel releases carbon particles and nitrogen oxides, and burning coal releases sulfur dioxide which leads to acid rain
• Nuclear power

  It is non-renewable, runs on uranium and plutonium
• Advantages of nuclear power

  • Does not release carbon dioxide
  • Extremely reliable
• Disadvantages of nuclear power

  • Highly dangerous radioactive materials
  • Decommissioning is extremely expensive and takes many years
  • Generates large amounts of highly dangerous radioactive waste
• Advantages of switching from coal to gas

  • Generates less carbon dioxide
  • Gas-fired power stations are flexible with short start-up time
• Renewable energy resource

  One that is being replenished as it is being used
• Renewable energy resources

  • Biofuels
  • Wind power
  • Hydroelectric power
  • Geothermal
  • Tidal power
  • Solar power
  • Wave power
• Advantages of renewable energy

  • Will never run out
  • Do not add carbon dioxide to the atmosphere
• Disadvantages of renewable energy

  • Wind and solar are not reliable
  • Hydroelectric power destroys habitats and is only useful in countries with lots of rivers
• Advantages of tidal power

  • Extremely reliable
• Advantages of wave power

  • Reliable and huge potential in the UK
• Advantages of geothermal energy

  • Reliable, uses heat from the earth
• Almost all cars in the UK run on petrol or diesel which are fossil fuels
• Biofuels

  Produced from plant materials, burning is carbon neutral