Energy

• What is a system?


  An object or a group of objects.
• What are the 4 different pathways by which energy can be transferred between stores?

  mechanically, electrically, by heating, by radiation.
• What does the principle of conservation of energy state?

  It states that energy cannot be created or destroyed, it can only be transferred from one store to another.
• What is efficiency?


  It is the ratio of useful energy output from a system compared to its total energy output.
• How do you calculate efficiency?

  efficiency= useful energy output/ total energy input *100
• What is a Sankey diagram used for?

  It is used to represent the energy transfers taking place.
• What are the three ways in which energy can be trasnferred by heating?

  Conduction, Convection and Radiation.
• What is conduction?

  The transfer of thermal energy through a solid by the vibration of particles.
• What is convection?


  It is the transfer of thermal energy through fluids by the upward movement of warmer, less dense particles.
• What is thermal radiation?

  The transfer of thermal energy through infrared waves.
• What are poor conductors called?

  Insulators.
• What is the main method of energy transfer by heating in solids?

  Conduction.
• What is the main method of energy transfer by heating in fluids

  Convection.
• Why are metals good at conducting heat?

  They contain delocalised electrons Which transfer the vibrations throughout the material.
• How do convection currents work?

  Particles get heated and expand

  They become less dense than the other particles

  They rise above the more dense particles

  Denser particles fall to the bottom

  This process is repeated
• What objects are the best at emitting and absorbing thermal radiation?

  Black , dull objects
• What objects are the worst at emitting and absorbing thermal radiation?


  White, shiny objects.
• What kind of thermal energy transfer does not require a medium?

  radiation
• How can we reduce conduction?

  By using insulators to prevent thermal energy from escaping.
• how can we reduce convection?

  Prevent fluids from moving.
• The effectiveness of an insulator is dependant on?

  the density of the insulator

  the thickness of the insulator

  the conductivity of the insulator
• How can we prevent heat loss in buildings?

  Using building materials that are good insulator

  Using roof insulation

  Double glazing
• What is work done ?

  energy transferred
• What is the formula for work done?

  Work done= force* distance
• What is the unit for work done?

  Nm or Joules
• What is GPE?


  The energy that an object has due to its height in a gravitational field.
• How do you calculate GPE?


  GPE=mgh
• What is the unit for GPE?


  Joules.
• What is kinetic energy?


  The energy an object has due to its mass and speed.
• How do you calculate kinetic energy?


  KE=1/2mv2
• What is power?


  It is the rate at which energy is transferred.
• What is the formula for power?

  Power= Work done/time
• What is the unit for power?

  Watts(W)
• What are the two types of energy resources?

  renewable and non-renewable
• What is a renewable resource?

  It is a resource that is replenished at a much faster rate than the rate at which it is being used.
• What is a non-renewable resource?

  resources that can not be replaced