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Homework Help: How do i find the current in this circuit?

  1. Aug 13, 2014 #1
    i did the question but im not sure if they are right. i wrote my answers on the attachment

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  2. jcsd
  3. Aug 13, 2014 #2
    is I1 and I3 .22A too because 0.22+0.22+0.22=0.65
  4. Aug 13, 2014 #3
    and can someone please explain how to find the Current if only the resistence and total voltage is given? and im confused on how to identify when some thing is a series or parallel when both are in a circuit together like this?

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  5. Aug 14, 2014 #4
    Well the answer here is you have both :) R1 and R2 are in SERIES with one another and they are then in PARALLEL with R3.

    Have you learned how to do voltage dividers and current dividers?

    A method to solve simple problems like this is to simplify first then solve.
    1) take the series resistors and make them into one (eg R4 = R1+R2)
    2) take the parallel resistors and make them into one (eg 1/R5 = 1/R4 + 1/R3)
    now you are left with a voltage source and a resistor. You can figure out I from I=V/R
    Next you have to do the fun part.
    Use a current divider equation to figure out the current through R4 and R3
    Then use a Voltage divider to figure out the voltage drop across R1 and R2.

    One thing I found extremely helpful which I'm all hesitant to post is this link http://www.falstad.com/circuit/
    its an online circuit simulator. I strongly suggest you use only to verify your answers and if you find your answer is wrong you can verify your steps (eg build the original circuit and the circuit after step 2 and check the currents and voltages still line up). I know people who used this tool to solve all their assignments and ended up failing the course cause they couldn't do the work on the exam.
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