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Homework Help: Calculating voltage across resistors

  1. May 8, 2007 #1
    Hi all,

    I am looking for a formula to work out the following-

    1megohm 10kohm

    what is X?

  2. jcsd
  3. May 8, 2007 #2
    Welcome to PF. Its not clear at least to me what the problem is, is X an unknown voltage. If so
    use V=iR first compute i using the total series resistance (here the sum of 1Mohm and 10Kohm.
    Then V is just the i*the resistance over which you want to find voltage.

    or all in one v=500*R/(R+r) This is just voltage divider eqn. Thats the voltage across the first resistance, voltage across the second would be:

    500*r/(R+r), if your looking for the value of x, this would be the one to use.
    Last edited: May 8, 2007
  4. May 8, 2007 #3
    voltage calculation

    Hi, on reflection it isnt very clear. Sorry.

    how about this-


    If R1 = 1Mohm and R2 = 10Kohm
    what is the voltage at X?

    Or this one -


    If R1 = 1Mohm, R2 = 10Kohm, R3 = 10Kohm and R4 = 10Kohm
    what is the voltage at X,Y and Z?

    is there a simple calculation for this problem?
  5. May 8, 2007 #4
    first find the electric current
    then use Ohm's law
    I = ?
    :grumpy: 1
    V = IR
    X - 0 = I(R2)

    :grumpy: 2
    V = IR
    500 - X = I(R1)
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