CP3: conservation of energy

• What happens to wasted energy in energy transfers?

  It will dissipate into the surroundings
• how is energy transferred?


  mechanically - forces moving through a distance

  electrically - by the use of an electrical current

  thermally - because of a difference in temperature

  radiation - by waves such as electromagnetic or sound
• what are the 8 main energy stores?


  • Chemical
  • kinetic
  • gravitational potential
  • elastic
  • thermal
  • magnetic
  • electrostatic
  • nuclear
• What are some ways that energy is transferred wastefully by mechanical processes?


  A rise in temperature caused by the transfer of wasteful energy this energy is dissipated into the system. In a mechanical system, energy is dissipated when two surfaces rub together called friction.
• what are some ways of reducing unwanted energy transfers in mechanical processes?

  lubrication
• what is efficiency?


  A way to describe how good a machine is a transferring energy
• how can efficiency be increased?


  Lubrication to reduce the friction between moving parts of a machine and increase the amount of useful energy transferred, or by reducing the wasteful dissipation of thermal energy to the surroundings, for example by using insulation.
• how do you calculate efficiency?


  E = Useful output/total output x 100
• what is the principle of conservation of energy?


  -Energy can’t be created or destroyed

  – Energy can only be transferred from one store to another

  – The amount of energy put into a system is the same as the total energy transferred by a system 
• what is electrical resistance?


  Opposition to the flow of the current, a high resistance means it is harder to flow through and low resistance means the current will flow more easily.
• What is thermal conductivity?


  The ability of a material to conduct heat.
• Give examples of non renewable resources 


  Nuclear fuels and fossil fuels
• Give examples of renewable resources


  Biofuel, wind, hydroelectricity, geothermal, tides, sun and water waves
• What is the equation used to calculate the change in GPE?

  Change in GPE = mass (kg) x gravitational field strength (N/kg) x change in vertical height (m)

  ∆GPE = m x g x ∆h
• What is the equation used to calculate the amount of energy associated with a moving object?

  Kinetic energy (J) = 1/2 x mass (kg) x speed ^2

  KE = 1/2 X m X v^2
• What is the energy change for an object projected upwards or up a slope?

  KE —> GPE
• What is the energy change for an object hitting an obstacle?

  KE —> sound
• What is the energy change for an object being accelerated by a constant force?

  the energy —> KE
• What is the energy change for an vehicle slowing down?

  KE —> heat
• What is the energy change for bringing water to boil in an electric kettle?

  Electric —> thermal
• Why is there no net change in the total energy is a closed system?

  • energy can flow in or out of the system
  • no transfer of mass