GCSE PHYSICS: Energy Transfer

GCSE PHYSICS: Energy Transfer

1. Radiation

   • The main type of radiation involved in heat transfer is the Infra Red Wave. It transfers the most amount of heat energy.
   • Some surfaces absorb and emit radiation better than others.
     • Matt black surfaces are great at absorbing radiation.
     • Reflective white surfaces are bad at absorbing and emitting heat
   • Radiation is the least efficient of the methods to transfer energy

2. Convection

   • The convection process is exactly that of which occurs within the earth's Mantle.
     • The magma in the mantle is about as thick as Jam
   • Firstly a particle with high energy rises through the fluid (or gas) transferring energy to other particles as it collides with them. If it has enough energy it can escape the fluid (Not GAS) if not however it simply floats back down to be reheated.
     • The process kinda looks like a circle when drawn out.
   • A liquid can be evaporated without the whole body of it reaching boiling temperature. (Like a puddle on a warmish day). Only some of the particles have the energy to escape the fluid. the ones that do escape take away from the net temperature of the body of liquid. On a cup of tea for example you blow the escaped particles away from the top so there is more of a concentration difference between the air and the water. This there for increase the rate of evaporation.

3. Conduction

   • Heat energy can move through a substance by conduction. Metals are good conductors of heat but non-metals and gases are usually poor conductors of heat. Poor conductors of heat are called insulators. Heat energy is conducted from the hot end of an object to the cold end.
   • Air and bad insulators such as plastic are used to insulate. A good example of this is overhead mains cables.
   • Heat always travels to colder area (like diffusion but with heat).
     • For example you can heat one end of a metal rod and the other end will eventually have a temperature increase due to conduction.

4. Insulation

   • Coffee cups in cafes tend to be made from polystyrene because it is a good insulator.
   • Installations such as cavity wall insulation remove conduction from the equation

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