conduction, convection and radiation

• which type of energy can be transferred by conduction, convection or radiation

  thermal energy
• what physical state does conduction take place in

  solid
• which physical state does convection take place in

  fluids - liquids and gaseous states
• what is thermal conductivity

  thermal conductivity is a measure of how well a material conducts thermal energy when it is heated
• the steps of how conduction work

  1. as one end of a solid object is heated, heat energy is transferred to the kinetic energy store of the particles in that end
  2. this cause the particles to vibrate faster, so they collide with neighbouring particles more frequently
  3. the collisions transfer kinetic energy, meaning the neighbouring particles also vibrate faster - and in turn collide more frequently with their neighbours
  4. this process repeats - energy is passed along the object =, form one particle to another
• how does convection work

  1. as a fluid is heated, the particles gain kinetic energy, and spread apart
  2. this means the heated fluid is less dense, and so it rises above cooler fluid
  3. as the fluid cools down it becomes more dense again, and so sinks below any warmer fluid
  4. if this process occurs in a limited space, such as container or room, it may create a convection current
• how heat transfer via radiation works

  all objects emit and absorb energy via infrared radiation. energy can therefore be transferred by one object emitting infrared radiation and another object absorbing it
• will a hot or cool object emit more infrared radiation

  the hotter the object, the more infrared radiation it will emit
• why a hot object cools down over time

  a hot object will emit more infrared radiation than it absorbs, therefore it will lose energy over time
• when a fluid is heated, does it become more or less dense

  it becomes less dense, as the particles gain energy and spread further apart