Unknown resistor value

Discussion in 'Homework Help' started by kwinterowd, Nov 28, 2011.

  1. kwinterowd

    Thread Starter New Member

    Nov 28, 2011
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    Need help finding value of R2
    Voltage source 115, R1 and R2 are in parallel, R1 100Ω, R2 100mA, R3 is in series R3 150Ω. Should be easy but...
     
  2. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
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    ...But apart from the fact that we are not likely to supply direct answers for somebody's circuit theory homework, however basic, we are not mind-readers.

    At the very least, post a schematic and explain your attempt to solve this. What is your difficulty with it?
     
  3. kwinterowd

    Thread Starter New Member

    Nov 28, 2011
    4
    0
    R1 100Ω
    +115v-- --R3 150Ω neg
    R2 100mA
    How do I calculate the resistance value of R2?
     
  4. kwinterowd

    Thread Starter New Member

    Nov 28, 2011
    4
    0
    115vdc R1//R2 + R3.
    R1=100ohm, R2=100mA, R3=150ohm
    I will try type circuit here.
    ,,,,,,,,,,R1 100 ohm
    +115v,,,,,,,,,,,,,,,,,,,,,,neg
    ,,,,,,,,,,R2 100 mA
    I don't know how to get the ohm value for R2. The textbook isn't very clear. Thanks
     
  5. kwinterowd

    Thread Starter New Member

    Nov 28, 2011
    4
    0
    Oops I forgot to put in R3
    ,,,,,,,,,,,,,,R1 100 ohm
    +115v,,,,,,,,,,,,,,,,,,,,,,,,,,,,,R3 150 ohm
    ,,,,,,,,,,,,,,R2 100 mA
     
  6. Georacer

    Moderator

    Nov 25, 2009
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    1,266
    If you want to use ASCII art to draw your picture, you should use the
    Code ( (Unknown Language)):
    1.  tags, available in the message toolbar, around your text to avoid automatic reformatting of your image.
     
  7. Adjuster

    Well-Known Member

    Dec 26, 2010
    2,147
    300
    Make a Thevenin equivalent for the two known resistors R1 and R3 and power supply from R2's point of view.

    Solve for the voltage across R2 given the known 100mA current draw.
     
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