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Potential difference

  1. Sep 17, 2005 #1
    what happens to the potential difference of a source of emf when a voltmeter is connected across its terminals?
    tanx. :smile:
  2. jcsd
  3. Sep 17, 2005 #2


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    HINT: Does current flow when the voltmeter is connected?
  4. Sep 17, 2005 #3
    hey tide,

    ideal voltmeters should have infinite resistance so as not to alter current but real voltmeters have finite resistance.does our voltmeter, in any way, still alter the current flowing through our set-up?
  5. Sep 17, 2005 #4


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    I assume that the source of EMF that you have in mind is a battery. Batteries have internal resistance and if there is current flowing through the battery then, by Ohm's Law, there must be a potential difference across the resistance.
  6. Sep 18, 2005 #5
    so, does the voltmeter affects the potential difference of a source?
  7. Sep 18, 2005 #6


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    Yes, the potential difference across the battery will decrease but still the emf of the source remains the same. The emf of a source is the energy supplied by the source per unit charge and is measured by the potential difference across the terminals, when no current is flowing through the source.
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