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Resistor Calculation

Discussion in 'General Electronics Discussion' started by tcrossman, Dec 21, 2010.

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  1. tcrossman


    Dec 21, 2010
    what size of resistor is needed to change 18VDC 1.1AMPS TO 18VDC 1AMP ?:eek:
  2. Resqueline


    Jul 31, 2009
    The formula for a series dropping resistor is R = delta U / I
    R = 0V / 0.1A(or whatever) = 0 ohms
    So, in other words, it doesn't compute. My brain responds with "syntax error" at the question.
    But if you just want to waste away the excess current with a parallell resistor then the formula is R = U / delta I.
    R = 18V / 1.1A-1.0A = 180 ohms. Power dissipation = U * I = 18V * 0.1A = 1.8W

    But maybe if you rather explain what you actually have there and what you need we might be able to figure out what you really need to do.
  3. AB2ZI


    Apr 24, 2009
    If it's just one resistor in a series circuit, then it's just R = E / I = 18 / 1 = 18 ohms. In the original circuit do you have a 16.36 ohm resistor now? 18 / 1.1 = 16.36 ohms...

  4. ljcox


    Jul 10, 2010
    Your question does not make sense. What are you trying to do?
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