Voltage and Resistors in Series

AI Thread Summary
Resistors in series experience voltage drops due to power dissipation, but the voltage across a resistor connected directly to a voltage supply is equal to the supply voltage. This occurs because the idealized wire connecting the resistor has no impedance, resulting in no voltage drop before the resistor. The voltage across the resistor can be defined as the difference between the supply voltage and the voltage drop across the wire, which is zero. Therefore, the voltage across the resistor remains equal to the supply voltage. Understanding this concept is crucial for analyzing circuits with resistors in series.
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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