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Homework Help: Current through a voltmeter with internal resistance

  1. Dec 20, 2009 #1
    1. The problem statement, all variables and given/known data
    You have a power supply of 10 V. It is connected in series to a 2 ohm resistor and a 5 ohm resistor.

    You take the voltage across the 5 ohm resistor with a voltmeter that has an internal resistance of 3 ohms. What is the current through the voltmeter?

    2. Relevant equations

    3. The attempt at a solution
    So I figured out the equivalent resistance of 5 ohms and 3 ohms is 1.815 ohms. Then the voltage across that is 4.83 V, which is the voltage read by the voltmeter.

    Is the current going through the voltmeter just the same as the current going through the entire circuit? (So 10/(2 + 1.815))

    Or is it the current just through the voltmeter's 3 ohm internal resistance? (Which I found to be 1.64 A)?
  2. jcsd
  3. Dec 21, 2009 #2


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    Homework Helper

    Equivalent resistance R = 5*3/8 = ? Check this calculation.
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