energy

• The main forms of energy are:

  • chemical
  • heat
  • electrical
  • sound
  • light
  • magnetic
  • elastic potential or strain energy
  • kinetic
  • gravitational potential
  • nuclear
• Energy can be changed from one form to another but cannot be created or destroyed. The total amount of energy does not change.
• types of energy…

  • heat
  • kinetic
  • magnetic
  • potential
  • light
  • electrical
  • chemical
  • elastic
  • nuclear
  • sound
• ke= 1/2mv^2
• pe=mgh .
• efficiency= useful output/ total input
• work done = force x distance moved

  work done= energy transferred
• energy reasources

  non renewable

  • nuclear
  • fossil fuels

  renewable

  • hydroelectric
  • wind
  • solar
  • tidal
  • geothermal
  • biomass
  • waves
• a renewable energy reasource is a source that will never run out
• a non renewable energy source is a source that will eventually run out
• oil and gas are no. renewable as they take millions of years to form and were heavily reliant on them as an energy source so were using them faster than they can be produced
• even though a small amount of uranium produces a large amount of electricity its a naturally occurring fuel and will eventually run out
• the process in which nuclear energy is obtained is nuclear fission.

  the fuels in the process are uranium or plutonium
• energy is what we need to do work
• the main uses of energy resources are heating and transport
• we should use energy as efficiently as possible because our main energy resources are fossil fuels which are non renewable, but if we use them efficiently they will last longer
• when generating electricity from fossil fuels…

  the boiler heats the water and changes it to steam

  the turbine converts the steams kinetic energy into potential movement

  the generator converts the potential energy to electrical energy

  the condenser then cools the steam back into water which then returns to the boiler
• there is large losses of heat in a electricity generator as the steam is at very high temperatures and transfers the heat to the surroundings
• the green house effect is when…

  light from the sun enters the atmosphere

  the earth warms

  heat is emitted by earth

  some escapes through the atmosphere

  some of this heat is absorbed by greenhouse gases in the atmosphere.
• green house gases include water vapour, carbon dioxide and methane
• effects of rising temperatures on earth…

  • polar ice caps melt causing a rise in sea levels leading to floods
  • more energy in the atmosphere causes extreme weather like storms
  • drought in place
• trapped air is a good insulator
• when a no. metal is heated at one end the atoms at that end vibrate faster

  they collide with their neighbours so they vibrate faster

  in this way the heat travels along the non metal
• conduction by a non metal is slow as the particles absorb the heat and vibrate and pass vibrations through the atoms of the structure.

  so energy is passed from one atom to the neighbouring atom, theres so many atoms in structures
• when a metal is heated at one end the atoms at the end vibrate faster and collide with neighbours which then vibrate faster. in this way heat energy travels along the metal.

  however in the metal there are also free electrons which move faster. they collide with neighbouring atoms so they also vibrate faster.
• conduction by a metal is fast as the free electrons move quickly and pass on their energy to other electrons
• the differences in conduction and convection

  • conduction is through solids, convection is through gases and liquids
  • convection heat travels upwards, conduction heat travels in any direction
• heat can’t travel through a solid by convection as convection is the upward movement of particles as they’re heated and particles can’t move from one place to another in a solid.
• dark matt surfaces are good absorbers of radiation
• light coloured shiny surfaces good reflectors of radiations
• dark matt surfaces are good emitters of radiation
• light coloured shiny surfaces are poor emitters of radiation
• ways to stop heat leaving your home from convection or conduction

  double glazed windows- two panes of glass with a vacuum between.

  cavity wall insulation- the cavity between the outer walls of a house can be filled with foam, fibre glass, polystyrene etc. this will trap air and reduce conduction

  draught exclusion- curtains, carpets, stuffed snake. as convection currents move through a heated room, cold air gets pulled through gaps in the doors, floors and windows.