energy

• a system is an object or a group of objects
• when a system changes, the way energy is stored in the system also changes
• energy can be transferred through heating, work done mechanically (through forces), work done electrically (when current flows) or through radiation
• specific heat capacity is the energy required to increase the temperature of 1kg of a substance by 1 degrees celsius
• specific latent heat is the energy required to change the state of 1kg of a substance without changing its temperature.
• power is the rate at which energy is transferred or work is done.
• energy cannot be created or destroyed, but can be transferred, stored or dissipated.
• energy waste can be reduced through lubrication which reduces friction so less energy is lost as thermal energy through friction.
• energy waste can be reduced through thermal insulation such as double glazing which means less useful thermal energy is lost (decreases thermal conductivity of the material)
• the higher the thermal conductivity of a material, the higher the rate of energy transfer by conduction across the material. This is because heat is allowed to travel through the material more easily.
• rate of cooling in a building is low if the walls are thick and the thermal conductivity of the walls are low.
• if the walls of a building were thin metal sheets, rate of cooling would be high because heat would be lost quickly due to the high thermal conductivity of metal.
• efficiency is the proportion of the energy supplied to a device that is transferred to the useful or intended store
• efficiency = useful energy output / total energy input
• efficiency of a device can be increased through:

  • lubrication
  • thermal insulation
  • recycling waste output energy
• main non-renewable energy sources are:

  • fossil fuels
  • nuclear fuels
• main renewable energy sources are:

  • biofuel
  • hydroelectric
  • wind
  • geothermal
  • tidal
  • solar
  • water waves
• renewable energy resources are resources that can be replenished as it's used
• non-renewable energy is used much more large-scale because they provide large energy outputs per kg compared to renewable resources (more efficient)
• renewable resources have become more important due to the finite lifetime of fossil fuels
• renewable energy can be less reliable
• the main energy uses include transport, electricity generation and heating
• environmental impacts of energy -- extraction:

  • fossil fuel extraction destroys habitats
  • wind turbines can be an eyesore for some people
• environmental impacts of energy -- uses:

  • fossil fuels release harmful emissions
  • solar and wind energy directly create energy with no harmful emissions
• during the industrial revolution fossil fuels became an important source of energy because it was easy to mine and provided lots of energy
• only recently has renewable energy become more suitable as technology has developed to harness renewable resources efficiently.
• specific heat capacity required practical: