heating from power dissipation
When thinking about heating you have to go through a number of different units to get some sensible numbers.

The electrical heat dissipation is measured in Watts.  The energy is measured in joules, and the heat itself is measured in calories.

Let's take a typical mug of water - say 300g of water (about 300cc, a typical coffee mug)  Now let's say we have something that gives off 10W of heat dissipation.  10W is all very well, but how long do we count the 10W for?  That's where the formula:


\$W=\frac{J}{t}\$


Where J is Joules, and t is time in seconds

comes in handy.  One Watt is one Joule per second.  So Joules = Watts × Seconds, ok?  So if we heat at 10W for 10 seconds, we get 100 Joules.

Now, the calorie is the amount of heat required to heat 1g of water by 1°C, and is equivalent to 4.184 joules.

That means that our 100 Joules is equal to (EDIT:  23.9 calories [1 calorie = 4.184 J, so 100 J * 1 calorie/4.184 J = 23.9 calories, not 418.4 calories]).  Over our 300g of water, that would be:


\$T=\frac{23.9}{300}\$


Which equals (EDIT:  0.08°C [not 1.395°C]) temperature rise.

So 10 watts of power for 10 seconds would raise the heat of the water in the coffee mug by a little under (EDIT:  a tenth of a degree [not one and a half degrees]).