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Homework Help: Need help with circuits question.

  1. Feb 2, 2009 #1
    1. The problem statement, all variables and given/known data

    3. The attempt at a solution

    i. First I combined 20ohm and 30ohm to make 50ohms. Since this 50ohms and 100ohms is in parallel I have to use 1/Rtotal= 1/r1 + 1/r2.... etc and got 33.333 ohms. I added this to 10ohms which ends up being 43.333 ohms. Then I used V=IR and got I=.277. So would .277 be the current going through 10ohm and half of that going through 100ohm and quarter of .277 going through 20ohm and 30ohm???

    So from here I would get half of .277 as current for 100ohm and a fourth of .277 as current for both 20 and 30 ohm. and using P=RI^2 i would get a total of 2.925W for power consumption??

    and with 2.925 I determine that it takes 3418.803419 hours to provide 10kJ of electrical energy??
    Last edited: Feb 2, 2009
  2. jcsd
  3. Feb 3, 2009 #2
    1. [itex] I = 0.277A [/itex] right? Total power consumption assumes the total resistance, which is [itex] R = 43.3\Omega [/itex], right? So when I carried out the calculation, I ended up with [itex] P = 3.322 W [/itex]

    2. [itex] P = 3.322 W = 3.322 \frac{J}{s}[/itex] Therefore, [itex] 10000 J = 3.322\frac{J}{s} \cdot x(s) [/itex], right? So you will end up with [itex] x = \frac{10000 J}{3.322\frac{J}{s}} = 3010(s) [/itex]

    [tex] \frac{3010}{3600}h = 0.836 h = 50.16 min [/tex]

    So 50 minutes and 10 seconds is what it takes to provide 10kJ of energy.
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