power rating of resistors?

Discussion in 'General Electronics Chat' started by stanman11, Mar 15, 2011.

  1. stanman11

    Thread Starter Member

    Nov 23, 2010
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    im trying to figure out if the bigger the resistor the more power it lets through or the mor power it blockes?
     
  2. Audioguru

    New Member

    Dec 20, 2007
    9,411
    896
    The physical size of a resistor determines how much heat it can transfer to air.
    Its value (the number of ohms) and the voltage or current determines how much it "blocks" or passes current flow.
     
  3. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Ohm's Law will help you understand the relationships between resistance, current and voltage.
    1 volt across 1 Ohm's resistance = 1 Ampere of current and 1 Watt of power.
    I=E/R; P=EI
    E=IR
    R=E/I
    Etc.
    It's a good idea to double your power requirement when selecting a wattage rating; that ensures your resistors will be able to dissipate the power.

    If you needed to use a 100 Ohm resistor with 10v across it, then the current would be 10/100 = 0.1A (100mA), and you would select a resistor that was rated for 10v*0.1A=1 Watt; double it for reliability = 2 Watts.

    http://www.allaboutcircuits.com/vol_1/chpt_2/1.html
     
    Last edited: Mar 15, 2011
  4. bertus

    Administrator

    Apr 5, 2008
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