topic 1

• what are the 8 energy stores

  1. gravitational potential
  2. elastic potential
  3. thermal
  4. nuclear
  5. electrostatic
  6. chemical
  7. kinetic
  8. magnetic
• how is energy transferred

  1. heating
  2. mechanically
  3. electrically
  4. radiation
• a system is a single object or a group of objects
• a closed system is when energy doesnt enter or leave its only transferred
• work done is the same as transferring energy
• specific heat capacity is the amount of energy needed to raise the temperature of 1kg of a substance by 1
• Specific heat capacity practical

  • Need block of material with 2 holes in it
  • Measure the mass of the block and wrap insulating layer around it to reduce energy transfer to surroundings
  • Insert a thermometer into one of the holes
• Measuring specific heat capacity

  1. Measure initial temperature of block

  2. Set the potential difference to 10V

  3. Insert heater into the other hole

  4. Turn on power and start stopwatch

  5. Measure temperature every minute
• Current does work on the heater

  Electrically transferring energy from power supply to thermal store then to the materials thermal store by heating
• Heating the block


  Causes the temperature to increase
• Calculating power and energy

  1. Calculate power supplied to heater with P=VI

  2. Calculate energy transferred to heater using E=PT
• energy can be transferred usefully stored or dissipated, but can never be created or destroyed
• dissipated energy is wasted energy that is being stored in a not useful way
• power is the rate of energy transferred or rate of doing work
• power is measured in watts
• 1 watt = 1 joule of energy transferred per second
• conduction is where vibrating particles transfer energy to neighbouring particles
• conduction

  1. energy transferred to object by heating is transferred to thermal store of object
  2. the particles in part of the object being heated vibrate more and collide with each other causing energy transfer between particles' energy stores
  3. this process continues throughout object until energy is transferred to other side of object where its usually transferred to thermal store of the surroundings
• convection is the transfer of heat by the movement of hot and cold air or water
• convection

  1. energy is transferred by heating to thermal store of liquid or gas
  2. particles can move faster when heated so the space between them increase this mean the density of the part being heated decreases
  3. as liquids and gases can flow the warmer and less dense particles will rise above the denser and cooler regions
  4. if there is a constant heat source it becomes a convection current
• thermal conductivity is a measure of how quickly energy is transferred through a materials
• convection current created by radiator

  1. energy is transferred from the radiator to nearby air particles by conduction
  2. air near the radiator becomes warmer and less dense so rises and is replaces with cooler air
  3. this process repeats
• making a product more efficient

  1. insulation
  2. lubricants
  3. streamlining
• there is rarely 100% efficiency the only acceptance is electric heaters, where the electrostatic energy is all transferred to useful thermal store
• lubricants reduce frictional force

  1. when something moves there is at least 1 friction force against it which causes energy to be dissipated
  2. a lubricant reduces the friction between 2 objects
• insulation reduces rate of energy transfer
• cavity walls - inner and outer walls with an air gap in the middle which reduces energy transferred by conduction through walls. the gap is often filled with foam which reduces energy transferred by convection in wall cavity
• loft insulators - fibreglass wool has pockets of air trapped. reduces energy lost by conduction and prevents convection current being created
• double glazing - two panes of glass separated by a small gap. stops energy being transferred by conduction from hotter pane to cooler one
• draught excluder - reduce energy transferred by convection
• investigating energy transfer

  1. boil a kettle and place water into sealable container and measure mass of water
  2. measure the initial temperature of water
  3. seal the container and leaver for 5 minutes
  4. remove the lid and measure the final temperature
  5. allow container to cool back to room temperature
  6. repeat with different materials wrapped around container
• non renewable means it will run out
• wind power

  1. each turbine has a generator which rotate blades creating electricity
• turbines can spoil the vies and are noisy, they can only work if there is wind present and need to be stopped if the winds are too strong, they also have a high initial cost
• wind turbines create no pollution and have minimal running costs
• solar cells

  1. charge batteries in calculators and watches
• solar cells create no pollution and are good in sunny countries
• solar cells only work during the day and have high initial costs
• geothermal power

  1. underground thermal energy
• geothermal energy can only be used in volcanic areas and has high costs