Physics - Conduction, Convection and Radiation

What is thermal conduction in solids?

In solids, atoms or molecules are held tightly in a lattice. When the metal is heated, particles gain more kinetic energy and start to vibrate, and collide with other particles nearby transferring their energy and causing them to vibrate. Energy being passed all the way through the solid causes an increase in temperature.

Why is thermal conduction bad in gases or liquids?

Atoms or molecules are too far apart so few collisions take place and vibrations are passed on much more slowly

Why are metals so good a conducting?

Metals have delocalised electrons which are free and able to move. When the metal is heated, the electrons gain more kinetic energy and collide with other electrons, transferring energy through the solid much quicker than vibrations

How does convection work in liquids or solids?

When parts of liquids or gases are heated, molecules or atoms undergo thermal expansion and becomes less dense. Therefore they rise and the cooler molecules or atoms moves to take their place. The process happens again when the hot molecules or atoms lose energy by colliding with slow moving particles and this is called a convection current

Radiation affects on earth

• Radiation emitted from the Sun travels to the Earth.

• Some radiation is reflected back into space by the atmosphere, clouds and the Earth's surface.

• Some radiation is absorbed by the atmosphere, clouds and the Earth's surface.

• The atmosphere, clouds and surface of the Earth also emit radiation.

• During the day the Earth absorbs more IR radiation from the Sun than it emits and so warms up. The opposite happens at night.

• On average, the Earth maintains a constant temperature where the IR absorbed equals the IR emitted.

 

• If we change the atmospheric conditions so that the Earth absorbs more radiation than it emits then the Earth's temperature will rise until absorption and emission are once again equal. This new higher temperature will cause climate change due to the global warming