Is the Formula for Voltage Drop Across Capacitor Opposite of Resistor?

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Discussion Overview

The discussion revolves around the calculation of voltage drop across capacitors in series, particularly comparing the formulas used for capacitors and resistors. Participants are exploring the relationships between voltage, charge, and capacitance in the context of a specific problem involving a 60uF and a 30uF capacitor powered by 60V.

Discussion Character

  • Homework-related
  • Mathematical reasoning
  • Conceptual clarification

Main Points Raised

  • One participant questions whether the formula for voltage drop across a capacitor is the opposite of that for a resistor, suggesting a comparison between the equations for resistors and capacitors.
  • Another participant points out that the symbols used in the initial equations do not make sense and emphasizes the need to derive the equations to ensure correctness.
  • A later reply stresses the importance of being able to derive the formula independently, using the relationship Q = C·V to analyze the situation.
  • There are repeated acknowledgments of confusion regarding the equations presented, with participants expressing uncertainty about the correct formulation.

Areas of Agreement / Disagreement

Participants express confusion and disagreement regarding the initial equations presented for voltage drop across capacitors and resistors. There is no consensus on the correct approach or formulation, and the discussion remains unresolved.

Contextual Notes

Limitations include unclear definitions of the symbols used in the equations and the need for derivation of the formulas to confirm their validity. The discussion also highlights the dependence on understanding the relationship between charge, capacitance, and voltage.

Joel Kee
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Homework Statement


I'm trying to calculate the voltage drop across a 60uF and a 30uF capacitor in series, powered by 60V. Is the formula for voltage drop across capacitor opposite of the formula for resistor, where resistor is R1=R1/(R1+R2) while capacitor is C1=C2/(C1+C2)?

Homework Equations

The Attempt at a Solution

 
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Joel Kee said:
Is the formula for voltage drop across capacitor opposite of the formula for resistor, where resistor is R1=R1/(R1+R2) while capacitor is C1=C2/(C1+C2)?
The symbols on the left side don't make sense. The right side is useful, but you should probably derive those equations to be sure.
 
mfb said:
The symbols on the left side don't make sense. The right side is useful, but you should probably derive those equations to be sure.
My bad, the eqs are supposed to be multiplied with the total voltage.
 
It is far better that you be confident at deriving such formula yourself using basic knowledge.

The crux of the matter is that when connected to a source, equal amounts of charge are added to each of the series-connected capacitors.
Use this fact, together with Q = C·V, to confirm or disprove the formula you wrote.
 
Joel Kee said:
My bad, the eqs are supposed to be multiplied with the total voltage.
Still your bad. R1=R1/(R1+R2) ? Etc.
 
rude man said:
Still your bad. R1=R1/(R1+R2) ? Etc.
V1=[R1/(R1+R2)]V

My bad.
 

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