What I've shown here is a potentiometer placed inside of a breadboard.

There are three wires coming out of a potentiometer, one we call point a,

the wiper, and point b.

The schematic of that is shown over here,

where the resistance between point b and point a does not vary.

That's the total resistance of that potentiometer.

It's the resistance when we measure the wiper to either of these points,

either this one or this one, that varies.

So, for example, if I took an ohmmeter and measured the difference between

the wiper and point b, I'm going to call that R sub v.

And that varies with respect to, in this particular case,

potentiometers have a dial on there that turns.

If I turn that, then I would find that this measurement varies in resistance.

So let's redraw this particular schematic term and

separate it out a little bit so we can examine the behavior.

So, we've got Rv measure between the wiper and

point b, and then this is what's left over.

So if this is a 100 ohm resistor then this would be a 100 minus Rv.