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Digital Voltmeters and Ohms?
How does a digital voltmeter work, and could you use it in a circuit with no load? If there was no load, wouldn't there be no resistance, and because V = IR, if R = 0 wouldn't V = 0 too?
If R=0 and you have a voltage source with infinite current capability, I=V/R and you would have infinite current going through that zero ohm load PLASMA (boom).
With a power supply or battery with current limiting, when you put a near zero load across the terminal, the power source limits the current through either an internal current limiting circuit, a crowbar which shuts off the power, or the battery puts our as much as it can until it either exhausts itself or goes into thermal runaway and blows up, like Nicads and Li-poly batteries do sometimes.
A DVM works by measuring the voltage difference between the + and - probe. Unlike a needle meter which bled off a tiny amount of current proportional to the voltage. This current went through a magnetic field to deflect the needle. Since there is no such thing as a true zero load circuit, the DVM will measure the overloaded potential of the power source.
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