Voltage and Resistors in Series

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Discussion Overview

The discussion revolves around the behavior of voltage across resistors in series, particularly focusing on the relationship between supply voltage and the voltage across individual resistors. The scope includes conceptual clarification and technical explanation regarding voltage measurements in electrical circuits.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • One participant questions why the voltage at a resistor in series is the same as the supply voltage, suggesting a misunderstanding of voltage drop and power dissipation.
  • Another participant clarifies that the voltage across a resistor is equal to the supply voltage when the resistor is directly connected to the supply, emphasizing that an idealized wire does not introduce any voltage drop.
  • A further response seeks clarification on the term "voltage at" the resistor, noting that voltage is measured between two points and asking if the original poster means the voltage across the resistor.
  • The original poster confirms that they are referring to the voltage across the resistor, indicating a focus on the potential difference between the terminals of the resistor.

Areas of Agreement / Disagreement

The discussion shows some agreement on the definition of voltage across a resistor, but there is a lack of consensus on the initial question regarding the relationship between voltage drop and supply voltage, indicating that the topic remains somewhat unresolved.

Contextual Notes

Participants have not fully explored the implications of different circuit configurations or the effects of non-ideal components, which may influence the discussion on voltage measurements.

nDever
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Hey guys,

I have a question about resistors in series. If resistors dissipate power which result in a voltage drop, then why is the voltage at the resistor the same as the supply voltage?
 
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nDever said:
I have a question about resistors in series. If resistors dissipate power which result in a voltage drop, then why is the voltage at the resistor the same as the supply voltage?

I assume you are talking about a resistor connected directly across the voltage supply?

Your supply defines the relative voltage across two nodes. Your voltage across the resistor is the same because its directly connected to the supply. An idealized wire doesn't have impedance and therefore doesn't cause a voltage drop, so there is no drop prior to the resistor (nor after). If you define your voltage supply as (V) and solve for zero drop across the idealized wire (R=0), you will find that the voltage across your resistor is (V - 0V).
 
Last edited:
nDever said:
Hey guys,

I have a question about resistors in series. If resistors dissipate power which result in a voltage drop, then why is the voltage at the resistor the same as the supply voltage?
Welcome to Physics Forums.

What do you mean the voltage "at" the resistor? A voltage can only be measured between two points. Do you mean the voltage across (i.e. the potential different between the two terminals of the resistor) the resistor?
 
Hootenanny said:
Welcome to Physics Forums.

What do you mean the voltage "at" the resistor? A voltage can only be measured between two points. Do you mean the voltage across (i.e. the potential different between the two terminals of the resistor) the resistor?

Thanks for the welcome.

Yes. I do mean the voltage across the resistor.
 

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