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Why can a voltmeter potentially load a circuit?

  1. Oct 22, 2005 #1
    Why can a voltmeter potentially load a circuit?
     
  2. jcsd
  3. Oct 22, 2005 #2

    Gokul43201

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    Let's say the internal impedance of the voltmeter is 1 MOhm. So, if you have a pretty high resistance circuit, and you are measuring the drop across say, a 1MOhm resistor, then you make the effective resistance 0.5 MOhm - that's a non-negligible effect.

    You want the internal impedance of the voltmeter to be large compared to the effective resistance across the points that you're measuring the voltage drop.
     
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