Potentiometer schematic

SgtWookie

Joined Jul 17, 2007
22,230
In the schematic I posted, everything is relative to ground, which always has a potential of zero volts.

One must have a point of reference for everything. I chose to place the ground near the negative terminal of the battery (voltage source). This is consistent with modern automotive design practice; IE: the negative battery terminal is grounded to the engine block, and from there the chassis is grounded to the engine block. This is not a "real" ground, but is a point of reference.

To get a "real" ground, you would take a 10' long copper-clad rod, and drive it into the earth. But even that is relative, if you want to beat a point to death ;)

Now since the Vsource is 10V, and we're measuring 1mA total current in the circuit, and the voltmeter is measuring 4V from the ground side to the wiper arm, what would you expect to measure from the wiper arm to the positive terminal of the Vsource?
 

SgtWookie

Joined Jul 17, 2007
22,230
Oh, OK - I see your confusion.

In the pictorial on the link, they don't differentiate between the DVM probes and the wiper arm connection; they look like all one thing. Electrically, they are. Physically, they are not. It's correct as a schematic, but to a newbie, it could be confusing.

What you did in YOUR schematic, is change the voltmeter to a short.

An ideal voltmeter has infinite resistance.

An ideal short has zero resistance.

Neither is possible, but... it's the thought that counts. ;)
 
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