Voltage Variation w/ Variable Resistor: Correct?

AI Thread Summary
The discussion clarifies that R2 is not a variable resistor, as its value remains constant regardless of the voltage measurement point. Instead, the voltage drop changes based on the location of the voltmeter probe along R2, affecting the measured output voltage. The concept is illustrated by comparing R2 to a resistive bar, where the voltage measurement varies without altering R2's resistance. A true variable resistor would have a schematic representation with two connections and a changing resistance value. The conclusion emphasizes that R2's role is misunderstood as a variable resistor in this context.
Lay1
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Homework Statement
Determine the minimum and maximum voltage from the voltage divider in the figure.
Relevant Equations
V=IR
V(drop)=Rx/Rt * Vs
20230411_194922.jpg

In this figure, I suppose the maximum voltage is when R2=1kohm and the minimum voltage is when R2=0kohm, which means R2 is a variable resistor. Is the way I think is correct or not? Please give me suggestions. Thank you.
 
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No. The value of R2 doesn't change. What changes is the portion of the voltage drop that is above or below the tap point where Vout measured. Imagine that R2 is a bar of resistive material, and you are changing the location of your voltmeter + probe along that bar. One extreme has the probe at the R3 end, the other is at the R2 end, but the resistors and currents don't change.
 
The variable resistor you described would be drawn like this in a schematic. It only has two connections, and it's value does change from 0 to the indicated value.
1280px-Variable_resistor_symbol.svg.png
 
DaveE said:
No. The value of R2 doesn't change. What changes is the portion of the voltage drop that is above or below the tap point where Vout measured. Imagine that R2 is a bar of resistive material, and you are changing the location of your voltmeter + probe along that bar. One extreme has the probe at the R3 end, the other is at the R2 end, but the resistors and currents don't change.
So, what you mean is that the voltmeter measures with R2 for maximum voltage drop and for minimum, without R2, but for R3. In all cases, R2 is not considered as a variable resistor. Thank you for your precious reply.
 
DaveE said:
The variable resistor you described would be drawn like this in a schematic. It only has two connections, and it's value does change from 0 to the indicated value.
View attachment 324752
Yes, thank you for your information.
 

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