Conservation of energy

• Recall and use the equation to calculate the change in gravitational PE when an object is raised above the ground

  change in gravitational potential energy = mass × gravitational field strength × height

  ∆GPE = m× g ×∆h
• Recall and use the equation to calculate the amounts of energy associated with a moving object

  kinetic energy = (mass × (speed)^2)/2

  KE = MxV^2/2
• Explain what is meant by conservation of energy

  Energy in a closed system remains constant

  Energy is not created or destroyed but merely changes forms

  Total energy of an isolated system remains constant over time

  Energy can be conserved from one from to another but it is always conserved
• What happens to the total energy of a closed system

  In a closed system there is no net change to the total energy
• why do mechanical processes become wasteful

  mechanical process become wasteful when they lead to a rise in temperature of the surroundings through heating . In all system changes , energy is stored in less useful ways .
• Explain, using examples, how in all system changes energy is dissipated so that it is stored in less useful ways


  For example the light and sound energy from a tv will eventually be absorbed by the walls and the people , leading to a rise in temperature
• Explain ways of reducing unwanted energy transfer

  Lubrication

  Thermal insulation
• Describe the effects of the thickness and thermal conductivity of the walls of a building on its rate of cooling qualitatively

  The thicker the wall the more thermal energy the wall absorbs so there is a lower temperature gradient between the outside and the inside . The thinner the wall the less thermal energy it absorbs so there is a high temperature gradient between the outside and the inside
• What is meant by the efficiency of a device 


  efficiency is a way of saying how food a device is at transferring energy into useful forms
• What is the equation for efficiency

  efficiency = useful energy transferred by the device / total energy supplied to the device
• Describe the main energy sources available for use on Earth

  Solar cells

  Bio fuels

  Tidal power

  wind turbines

  hydroelectricity

  nuclear fuels

  fossil fuels
• what is a renewable energy source

  energy sources that wont run out ,most do not emit carbon dioxide and do not cause pollution
• give some examples of renewable energy sources

  wind turbines - use kinetic energy from the wind to generate electricity

  tidal power - uses the rise and fall of the tide to generate electricity

  bio fuels - animal or plant matter used to produce thermal energy or used to power cells
• what is a non renewable energy source

  resources that will eventually run out

  they are available all the time unlike some renewable sources
• give some examples of non renewable sources

  nuclear fuels ( such as uranium ) - used to generate electricity . as energy sources in space crafts

  fossil fuels ( coal , oil and natural gas ) - used to generate electricity to power transport , heat homes and for cooking
• Explain patterns and trends in the use of energy resources

  The use of energy sources has risen over the years due to :

  the worlds population has increased

  technology is more developed which requires more energy

  electrical energy - power stations require fuels in order to generate electricity

  in more recent years there has been in an increase in the use of nuclear fuel and hydroelectric power