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Resistors in seris and in parallel

  1. Mar 6, 2013 #1
    I have this question
    I need to Find Voltage, Resistance and Current in all resistors and total.
    This is what I did so far.
    Added 13ohms +15 ohms, then took all 3 of those and made it into one, whihc gave me 7.2258ohms.
    Did the same for the 72 and 45 to get 27.7 ohms.
    Then found the total resistance as 77.92 ohms. Found I total , current to be 1.54A
    And for the 19ohm resistors I got V=29.26V I=1.54A
    For 24ohm, V=36.96 I=1.54A
    And I think for the 32 ohm V=29.26 I=0.91A
    For 72ohm and 45 ohm V=27.7ohm and if that is it, should total current equal 1.54 instead of 0.88A?
  2. jcsd
  3. Mar 6, 2013 #2


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    Gold Member

    I take it we are supposed to psychically devine what voltage is across the string? :smile:
  4. Mar 7, 2013 #3
    I just did, it's 120 V.

    The voltage across the 32V resistance is wrong.
    To determine the voltage across parallel resistances, you first use ohms law on the equivalent reistance, so you multiply the equivalent resistance (wich was 7.2258 ohm), with the total current, to get the voltage across all the parallel resistances. Then you find out all the currents through individual resistances by using ohms law on the individual resistances.

    This goes for the 72 ohm in parallel with 45 ohm too.
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