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Voltage drop

Discussion in 'General Electronics Chat' started by alok1982, Sep 21, 2017.

  1. alok1982

    alok1982 Member

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    Hi,
    I had connected a 10 Mega ohm resistor across the 5Vdc. Another end of resistor is kept open (floating).
    When I measured voltage at another point it shows 4.5V.

    Why this drop happens?
     
  2. Triode

    Triode Member

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    It shouldn't. Did you verify that it's actually 5V before the resistor? Sometimes power adapters can be a bit off, and it's normal for old batteries to be low.
     
  3. atferrari

    atferrari Well-Known Member

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    Simple as it seems, show the circuit and the points where you measured that voltage.
     
  4. dave

    Dave New Member

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  5. ericgibbs

    ericgibbs Well-Known Member Most Helpful Member

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    hi 1982,
    From your description it suggests you had connected the meter in series with 10meg resistor.?
    The meter has internal resistance, so current will flow through the 10meg and the meters resistance, this current will cause a voltage drop across the 10meg.

    eg: assume your meter had a 10meg internal resistance, when connected in series with another 10meg connected to 5V, the meter would read 2.5V.
    E
     
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