4b - Convection and efficiency

Conduction

The direct transfer of heat from one substance to another substance that it is touching through vibrating atoms

Factors affecting conduction

As an atom is heated up they vibrate more meaning more collisions occur, transfers energy from one to another. Materials are good at conducting heat as delocalised electrons can collide with atoms helping more collisions

What is an insulator

Does not conduct well which makes it a good insulator to prevent energy leakage and transfer by conduction

Convection

Main way energy is transferred in liquids and gasses, Convection cannot occur in solids

Convection currents

When a liquid or gas is heated, molecules push each other apart making the fluid expand which makes hot fluid less dense than surroundings, Hot fluid rises and cooler fluids move in to take its place. Eventually the hot fluid cools and contracts and sinks back down as it is more dense

Thermal Radiation

All objects emit radiation, the hotter the object the more infrared radiation is released

Factors affecting Thermal Radiation

The colour of the object - Matte black absorbs and emits more radiation. Glossy white objects are the worst at emitting and absorbing thermal radiation as they reflect.

Reducing energy loss

Insulators are used to prevent energy loss, it prevents convection currents and the fluid from moving.

Insulation

Reduces energy transfers from both convection and conduction and the effectiveness of a material can vary

Factors affecting insulation

- lower thermal conductivity the less energy is transferred

- Less dense, the further apart the particles are, hardy for energy to transfer

- Thickness, The thicker the better

- Trapped air, air is a poor conductor fibres can trap air which makes them good insulators