Understanding Voltage in Parallel RC Circuits

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Discussion Overview

The discussion centers around the behavior of voltage in parallel RC circuits, specifically whether a resistor and capacitor in parallel share the same voltage. The scope includes conceptual understanding and technical explanations related to electrical circuits.

Discussion Character

  • Conceptual clarification, Technical explanation

Main Points Raised

  • One participant asserts that a resistor and capacitor in parallel have equal voltage, referencing basic circuit principles.
  • Another participant suggests consulting Kirchoff's laws to understand the consistency of electrical circuit rules across various situations.
  • A different viewpoint emphasizes the practical measurement of voltage using a voltmeter, indicating that measuring across the capacitor is equivalent to measuring across the resistor due to their connection.
  • Another participant notes a rule regarding the potential on a wire being the same throughout, but adds that this may not hold if wire resistance or significant lengths are involved, particularly in high-frequency AC scenarios.

Areas of Agreement / Disagreement

Participants generally agree that a resistor and capacitor in parallel have the same voltage, but there are nuances regarding the application of this principle in certain conditions, particularly involving wire resistance and AC effects.

Contextual Notes

Some limitations are noted regarding the assumptions of ideal conditions in circuit diagrams, as real-world factors like wire resistance and impedance may affect voltage measurements.

member 392791
Hello,

I know that if two resistors are in parallel or two capacitors, they have the same voltage.

However, is it the case that a resistor and capacitor in parallel also have equal voltage?
 
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Yes...
 
Look up the basics of electrical circuits - Kirchoff's laws etc.. It's all very consistent stuff and the rules apply over a huge range of situations.
 
Think about using a voltmeter to measure the voltage across the resistor or capacitor. You put the probes across the capacitor's wires - but these are connected to the resistor's wires - so you might just as well say that you're connecting the voltmeter across the resistor. There is only one voltage involved, whether you measure it 'across the resistor' or 'across the capacitor'.
 
Always apply this rule to circuit diagrams: The potential on a wire is the same all the way along it.

So the potential difference between two wires, connecting any number of components, will be the same everywhere. This, of course, may not apply if the wires have resistance or they have a significant length and (high frequency) AC is involved. In this case, a proper circuit diagram should really have included explicit extra resistances and Impedances.
 

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