Voltage Variation w/ Variable Resistor: Correct?

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Homework Help Overview

The discussion revolves around the behavior of voltage in a circuit involving a variable resistor and a fixed resistor, specifically focusing on the interpretation of voltage measurements across these components.

Discussion Character

  • Conceptual clarification, Assumption checking

Approaches and Questions Raised

  • The original poster attempts to understand the relationship between the variable resistor and voltage levels, questioning whether the maximum and minimum voltages correspond to specific resistor values. Some participants clarify that the resistor value does not change, but rather the measurement point affects the voltage reading.

Discussion Status

Participants are exploring different interpretations of how voltage is measured in relation to the fixed and variable resistors. There is an ongoing clarification regarding the nature of the variable resistor and how it is represented in schematics, with some guidance provided on the concept of voltage drop across resistive materials.

Contextual Notes

There appears to be some confusion regarding the definitions and roles of the resistors in the circuit, particularly in terms of their variable or fixed nature and how this affects voltage measurements. The discussion does not reach a consensus on the original poster's assumptions.

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.
 
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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.
 
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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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