captaincaliena1206 wrote:
If I don't have the fan on, the top of the iMac gets red hot to the point where I almost burn my hand.
FWIW, the top of all aluminum body iMacs
feel unusually hot in comparison to the plastic body ones, but a large part of that is because aluminum is a very good conductor of heat & plastic is a poor one. Apple takes advantage of that fact to conduct away some of the heat from the internal parts to the aluminum case that in the plastic body models would have to be carried away by the air the fans blow through the case. This results in quieter operation because the fans can run slower. Since what matters is not the temperature of the case but of the heat-sensitive internal parts, this often leads users to think the aluminum body iMacs run much hotter than the plastic body ones when it isn't true.
If you are skeptical about this, try this experiment:
Heat up a coffee cup full of water to a little below the boiling point. Set a plastic spoon & a metal one into the cup & let them both heat up to the water temperature. If you touch the handle of each one briefly, the metal one will feel like it is about to burn you but the plastic one won't, even though they are actually at the same temperature. That's because metal is a better conductor of heat than plastic so it transmits heat to your skin faster & raises your skin temperature more quickly.
The same thing happens when you touch the cases of the iMacs. The aluminum ones feel hotter even when they are at the same temperature as the plastic ones. What matters is how hot the insides get, but you can't judge that by how hot the outside gets. For that, you need some tool like iStat Pro that reads the temperature of various internal systems.
