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High power resistor ratings

  1. Sep 16, 2014 #1
    I'm looking for a high power resistor. I just got confused over some nomenclature I haven't seen before. (Yes I'm a beginner). I'm seeing resistors named like this: "3R9ohm"and "4R7ohm" I know what R is in V=IR. But in the rating of a resistor? Can someone help?
  2. jcsd
  3. Sep 16, 2014 #2


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    Power rating (in Watts) is a totally different thing to the resistance of a resistor

    your 3R9 and 4R7 are the resistive values ie. 3.9 and 4.7 Ohms respectively

    resistors can be purchased with all sorts of power ratings from ~ 1/8 Watt to 100's of Watts
    for every day electronics ( maybe higher wattage ratings in high voltage/current situations )

  4. Sep 16, 2014 #3


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    Staff: Mentor

    The power rating is all about getting rid of heat, so transistors rated for a high power are typically quite large. If you do not know what resistance values mean, I'm not sure if you really need a high power resistor. What is the purpose of the resistor?
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