How does Archimedes' principle relate to convection?

Answer 1

Fine question.

In a nut shell, Archimedes' principle tells us how things float (buoyancy). Things float when they are lighter than the amount of water (I say water....could be any non-solid medium, it tells us why helium balloons fly away and etc) they displace. This means they have less density (mass per unit volume).

In convection, cool parts sink and gain heat energy. They then expand due to the heat, rise away from the heat source and cool off. Archimedes' principle explains why this occurs because as things increase in temperature - they expand. Expanding means you have more volume for the same mass (thus less mass per unit volume and so less density). So we can see why the hot material moves upwards and the cool material moves downwards (as it is more dense than the hot material).

This forms a continual cycle that we know as convection.

If this is at all confusing, try googling 'convection' and just find some clear animations (there should be a fair few) of the cycle. You'll have it in no time.