1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Heat generation in electric appliances

  1. Feb 9, 2009 #1
    This is my first post on these, so let me introduce myself. I'm 30 year olds and I work in the HVAC-R industry. I live in Norway, so bear with me on my English, which might be somewhat "off" some places.

    As we all know, power consumption in all electric appliances equals heat. I know that some of the power will be used to make light as well, depending on the appliance, but of course, all this light will become heat after a little while.

    I'm having a heated debate with some guy on some site in English, and I am having problems proving this to him. I have given him a few sources, but sources like wikipedia will of course not make him admit he was wrong. (I really don't blame him for this, although on this topic it is accurate.)

    So what I'm asking here: Since I'm Norwegian, and having a bit of a problem explaining this to him, I ask if you could help me.

    I need some really reliable sources on this. This would be greatly appreciated.
  2. jcsd
  3. Feb 9, 2009 #2


    User Avatar

    Staff: Mentor

    First of all, your English is excellent. Even the pun about the "heated debate"... excellent.

    The best way to approach it is to look at the appliances one by one, and account for where the energy input goes. For example, with a stereo, you can end up with a moderate fraction of the energy being radiated as sound, not heat. But in general, most of the energy will end up as heat somewhere.
  4. Feb 9, 2009 #3
    I guess it depends on how you define appliance. If you're only talking stoves and ovens and refrigerators and irons and so on, you're close enough. The Hoover is not always so close. Wiki wouldn't convince me either.
  5. Feb 9, 2009 #4
    I'm familiar that some of the energy that comes out is vibrations and sound, and even this will eventually turn into heat, cause no sound or vibration is sustained forever. Not even on a Gibson Les Paul. Of course, the sound and vibration probably leaves the room.

    I'm not sure if you are familiar with the gaming consoles: PS3 and XBOX 360.

    He stated that the 360 heats up his room 10 degrees more than his PS3.

    Tests show that the PS3 on average consumes 5-8W more than the 360, and since the PS3 has a higher power consumption, it surely must generate more heat? I'm not talking about heating the processor of the two consoles, but the room. It's also a known fact that the 360 sounds like jet plane in comparison to the PS3, so a lot more vibrations and sound from the 360.

    I've tried to show him that he is wrong in many examples, but he just won't admit he is wrong.

    So, are there any reliable sources that would be appropriate to give this guy?
  6. Feb 9, 2009 #5
    Something's not quite right IMNHO. He's saying, in effect, that a 180W power supply heats a room to 10 degrees hotter than a 190W power supply. I've never used either console, but I'm guessing they're two person games? If so, those two persons, if they are moving about excitedly, might be putting out 400-600W. If the room is tiny and well insulated, a really active game might raise the temperature 10 degrees more than a quiet game, though that sounds like a huge temperature rise. Are the games comparable? Does that question even make sense? Can you tell us about the room?
  7. Feb 9, 2009 #6
    He's saying, in effect, that a 180W power supply heats a room to 10 degrees hotter than a 190W power supply.

    I cannot tell you about the room, although I'm guessing an average living room, but I raised an eyebrow as well when I heard it.

    These are video gaming consoles, by the way.
    He only uses one console at a time, since he says one of them heats the room more than the other.
  8. Feb 10, 2009 #7


    User Avatar
    Science Advisor

    Personally I have played both, and own several consoles. Firstly, unless his room is about 10 cubic feet larger than the volume formed by his TV and the console, then its not heating up 10°. I have a medium-sized living room, and my PS3 doesn't heat it up any negligible amount.

    More on a heat transfer side, I would argue that in non-moving electronics such as video game consoles, then yes, all of that energy consumed should at some point be converted to heat.

    However, there is also a transient effect here. The XBOXs have had problems overheating. The newer ones may be designed to wick away the heat better from the actual console. My PS3 gets blazing hot, but it doesn't seem to transfer much heat to the air around it. In essense, perhaps the XBOX is simply better at heat transfer.

    Since these things are made to be on for hours at a time, and since to reach steady state in a large room such as a living room might take a while with constant heat generation, a proper test would require these machines to be on for quite a while.
  9. Feb 10, 2009 #8


    User Avatar
    Science Advisor

    Hi RRhoads,

    It sounds as if you simply need to refer him to any thermodynamic text for the numerous examples of how energy is transformed. The consequence is that some portion, but not all, energy is converted to heat due to irreversibilities inherent in all machines.

    Simply put, the energy input to the system less the energy output is equal to the change in energy of the system. Therefore, if the output is less than the input there must have been a loss somewhere. For example, if you use 1000 watts of electrical power to run an electric motor, and you only get 900 watts output at the shaft, then you have lost 100 watts. Where exactly the loss is attributed, depends on the machine.

Share this great discussion with others via Reddit, Google+, Twitter, or Facebook