Another newbie question

  • Thread starter jaydnul
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So i was dinking around with my multi meter and i noticed that if you touch the positive end of a battery and the negative end of a different battery, there isnt a voltage being measured. Why is that. I would think that an excess of electrons would wanna rush to any area that had a depletion of electrons, even if it wasn't in the same battery.
 

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berkeman
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So i was dinking around with my multi meter and i noticed that if you touch the positive end of a battery and the negative end of a different battery, there isnt a voltage being measured. Why is that. I would think that an excess of electrons would wanna rush to any area that had a depletion of electrons, even if it wasn't in the same battery.
You need a complete circuit to measure a voltage. A small current has to flow to charge up the input capacitance of the DMM and to drop a voltage across the input resistance of the DMM. Without a real complete circuit, you don't have that.

An exception to that is if you put your DMM on AC voltage measurement, and hold the two leads with your two hands. You will likely see a small AC voltage, which is from AC mains noise coupled capacitively into your measurement...
 

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