Does power rating mean the same thing as Power dissipation?

Discussion in 'General Electronics Chat' started by worldHello, Oct 18, 2014.

  1. worldHello

    Thread Starter New Member

    Oct 15, 2014
    I know power rating means the power an element can handle.
    For example, if a 2-ohm resistor has power rating of 1W, then a current of 1A yields V=2 V, and P = 2*1=2 W. 2 W > 1W, so the resistor will be damaged and overheated.

    Does power dissipation mean the same thing?
    I personally think so, but would like to have more confirmation.

  2. crutschow


    Mar 14, 2008
    Yes, the power rating is the power the device can dissipate, typically at 25C ambient temperature. Normally, for good reliability, you don't want to operate the device at much above about 50% of its rating.
  3. worldHello

    Thread Starter New Member

    Oct 15, 2014
    Thank you. If a device's power dissipation is "internally limited", what does it mean?

    I understand it means it dissipates very minor power, but I guess it should have some kind of power rating that tells you how much power it can handle, right?
  4. bertus


    Apr 5, 2008

    Most voltage regulators have a thermal protection.
    The regulator will limit or even shutdown when the device gets to hot.

  5. GopherT

    AAC Fanatic!

    Nov 23, 2012
    They are the same unless you are buying a ShopVac! "...may not be indicative..."

    Horsepower Rating
    Peak horsepower is the maximum output horsepower of a motor determined from a laboratory dynamometer test. Since peak horsepower is outside the normal operating range of a vacuum cleaner, it may not be indicative of actual air power differences when comparing two cleaners.
  6. studiot

    AAC Fanatic!

    Nov 9, 2007
    No it doesn't, quite.

    The power dissipation is the actual power dissipated.
    So in your resistor example if the current was only 0.5 amps then the power dissipation in your 2ohm resistor would be only 0.5 watts
    But its power rating would still be 1 watt.

    The power rating is the maximum power the device can safely dissipate in normal working at a given temperature.

    You should always note the given temperature because a device may require cooling measures to achieve this.
    There are formulae for derating (reducing the rated power) for operation at higher temperatures.