Simple Resistance Question

Discussion in 'Homework Help' started by ElectronicsFanatic, May 9, 2012.

  1. ElectronicsFanatic

    Thread Starter Member

    Feb 12, 2012
    30
    1
    I am a little confused by where exactly I am supposed to be measuring for voltage. Here is the question:

    What is the voltage, with respect to Ground, measured at the point where R1 and R2 connect?

    So does that mean that I am measuring from this point to this point?

    [​IMG]

    Or am I measuring from this point to this point?

    [​IMG]

    If it is the later, than it would be 0V, but if it is the first then it would be 18V
     
    Last edited: May 9, 2012
  2. WBahn

    Moderator

    Mar 31, 2012
    17,720
    4,788
    Read what you are supposed to do carefully.

    What is the voltage

    1) with respect to ground

    measured at

    2) the point where R1 and R2 connect.

    What are the two points mentioned in those instructions?
     
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  3. hibell

    New Member

    May 8, 2012
    5
    2
    I think it wants the point between R1 and R2 with ground. So one lead would be connected between R1 and R2 and the other between R3 and V1. This would measure the voltage across R2 and R3 if I am not mistaken.
     
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  4. ElectronicsFanatic

    Thread Starter Member

    Feb 12, 2012
    30
    1
    ok so if I take a little more time to read the question based off of the hints from WBahn and hibell, then I should be measuring from these two points?

    [​IMG]

    And that would turn out to be 30V
     
  5. WBahn

    Moderator

    Mar 31, 2012
    17,720
    4,788
    Correct. Including the polarity.

    When you measure A relative to B, you assume that A is the positive node and B is the negative node.
     
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  6. hibell

    New Member

    May 8, 2012
    5
    2
    That looks correct. By voltage division, (8e3 + 12e3)/(8e3 + 12e3 + 4e3) * 36 V = 30 V which also makes sense due to more resistance should have higher voltage (20 k versus 4 k) due to Ohm's law.
     
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