topic p1- energy

• energy stores

  • kinetic
  • thermal
  • gravitational potential
  • elastic potential
  • chemical
  • electrostatic
  • magnetic
  • nuclear
• how can energy be transferred

  • heating
  • doing work
  • by falling
• energy being transferred- energy stores- example

  
• kinetic energy

  
• kinetic energy

  energy (joules- j) = 1/2 x mass (kg) x (velocity)^2 (m/s)
• gravitational potential energy- Ep=mgh

  energy (j) = mass (kg) x gravitational field strength (N/kg or m/s^2) x height (m)
• elastic potential energy

  
• elastic potential energy

  energy (j) = 1/2 x spring constant (N/m) x (extension)^2 (m)
• specific heat capacity

  • energy required to increase the temperature of 1kg of a substance by 1 degree c
  • all substances have a different SHC
• the equation for specific heat capacity

  
• the equation for specific heat capacity

  energy change (j) = mass (kg) x shc (j/kg degrees celcius) x temp change (degrees celcius)
• the conservation of energy

  energy can never be created or destroyed, only transferred usefully, stored or dissipated
• dissipated

  wasted
• power

  power is the rate of doing work
• P = E / T

  power = energy / time
• P = W / T

  power = work done / time
• conduction

  • occurs in solids
  • the process where vibrating particles transfer energy to eachother

  
• convection

  • occurs in liquids and gases
  • the process where energetic particles move away from hotter to cooler regions

  
• reducing unwanted energy transfers

  • cavity wall insulation
  • loft insulation
  • draught excluders
  • double glazed windows
• efficiency

  • efficiency = useful output / total input x 100
  • nothing is always 100% efficient
  • there is always dissipated energy, mostly due to heat / sound
• energy resources- renewable

  • solar
  • wind
  • hydro-electric
  • bio-fuel
  • tides
  • geothermal
• energy resources- renewable

  • never run out
  • do less damage
  • unreliable
• energy resources- non-renewable

  • fossil fuels
  • coal
  • oil
  • (natural) gas
  • nuclear
• energy resources- non-renewable

  • reliable
  • will run out
  • damage environment
• the national grid

  
• the national grid

  • uses transformers to reduce unwanted energy transfers when transporting electricity
  • step up transformers increase the voltage, which reduces the current and causes less energy loss due to heat
  • when the power reaches, step down transformers bring the power back to 230V, a safe amount