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Does a variable resistor add or subtract voltage?

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1. Does a variable resistor add or subtract voltage?
Also if you look at the attached image of a circuit below, which of these is correct:

(note that V = voltage)

Vx = V1 + V2

OR

VY = V1 + v2

2. Re: Does a variable resistor add or subtract voltage?
I'm not sure that I understand what you mean by Vx and Vy. Presumably V1 and V2 are the potential differences across their respective resistors. Are Vx and Vy across anything?
3. Re: Does a variable resistor add or subtract voltage?
What do you mean by Vx and Vy here?
Normally you would just use the emf (or terminal pd) of the cell and call it V.
Then V = V1 + V2

Add to or subtract from what?

The pd across the variable resistor can increase (if R increases) or decrease (if R decreases).
So it can have a larger or smaller proportion of the value of V depending on that.

4. Re: Does a variable resistor add or subtract voltage?
(Original post by Pangol)
I'm not sure that I understand what you mean by Vx and Vy. Presumably V1 and V2 are the potential differences across their respective resistors. Are Vx and Vy across anything?
Vx and Vy aren't across anything (component-wise), they're just showing the volts on their respective parts of the circuit.
5. Re: Does a variable resistor add or subtract voltage?
(Original post by Red Richie)
Vx and Vy aren't across anything (component-wise), they're just showing the volts on their respective parts of the circuit.
Do you mean the instantaneous potential at that point in the circuit ? :/
6. Re: Does a variable resistor add or subtract voltage?
Voltage is a difference in potential.

You seem to be mixing potentials and potential differences.

A person has a height of 1.3m but this represents the difference in position between the sole of their foot and the top of their head.

The cell voltage in your circuit would appear to be the difference between Vx and Vy (if those represent individual potentials)

So Vx-Vy = V1 + V2 (assuming V1 and V2 are the p.d.s across the resistors)
Last edited by Groat; 28-05-2012 at 21:35.

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Last updated: April 11, 2012
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