Originally Posted by markrubin
The amount of power that goes in does not simply equal the amount of heat the is generated by the appliance
. Some of the energy produces the picture you're watching. Some also produces the sound you're listening to.
My claim that "all power into the set turns into heat in the room
" is correct, almost. The quoted statement above is correct without any disclaimers. The subtle difference between the two claims is highlighted.
The power that goes into a TV set turns immediately into heat in the resistive elements of the set when current flows through them. Majority of this energy escapes the set as hot air by convection, while a much smaller amount is conducted.
Another form of energy leaving the set is the screen light radiation. This form energy will hit the targets such as the walls, people, pictures, etc. where it will be absorbed and turned into heat. A small part will be reflected and bounce around until eventually it is all aborbed and turned into heat.
Another form of energy leaving the set is the sound. As above, it will turn into heat by causing vibrations in the walls and other lossy objects.
Another form of energy leaving the set is RF radiation. The FCC regulations require that it be less than the allowed limits but it is not zero. This energy will, just like in a microwave oven, turn into heat.
With all that energy getting into the room, without the exactly equal amount escaping, the room temperature would reach infinity and everybody in it would die. Luckily, the elevated temperature in the room causes the energy to be transferred to the rest of the house and, eventually, into the air outside.
The same applies to the three other forms of energy I listed. Some sound escapes and we hear what our friends next door are playing. If there are windows, some light energy escapes through them. In that sense, my claim is not 100% correct as it does not, for simplicity, account for these three forms of energy escaping the room. Whatever will fail to escape, will turn into heat.
Admittedly, the direct heat generated by the resistive elements in the set accounts for most of the input energy so that the other three are mentioned just for the record as an exercise in hair splitting.