How current relates to capacitance

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    Capacitance Current
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Discussion Overview

The discussion revolves around the relationship between current, resistance, and capacitance in a simple circuit consisting of a battery, resistor, and capacitor. Participants explore how adding resistors affects the charging time of the capacitor, focusing on the mathematical relationships involved.

Discussion Character

  • Technical explanation, Mathematical reasoning, Conceptual clarification

Main Points Raised

  • One participant suggests that adding additional resistors will increase the charging time because it decreases the overall current.
  • Another participant agrees with this assertion but notes that the effect would differ if the resistors were connected in parallel.
  • A third participant emphasizes the importance of using mathematical descriptions, stating that the time constant (RC) determines the charging behavior and that the current decreases exponentially as the voltage across the resistor changes.
  • A later reply reiterates that a larger resistance results in a longer time for the current to decrease, thus increasing the time required to charge the capacitor.

Areas of Agreement / Disagreement

Participants generally agree that increasing resistance leads to longer charging times for the capacitor due to decreased current. However, there is a note of conditionality regarding the configuration of the resistors (series vs. parallel), which introduces some complexity into the discussion.

Contextual Notes

The discussion assumes a series configuration of the circuit components and relies on the mathematical relationship between resistance, capacitance, and current without resolving any potential ambiguities in definitions or assumptions.

JFS321
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Hi all,

I have a simple circuit with a battery, resistor, and finally, the capacitor.

Am I correct in saying that adding additional resistors will increase the charging time, because adding resistors will decrease the overall current?

Thanks--
 
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Basically...yes...with the information you have provided!

PS...unless you connect the resistors in parallel
 
JFS321 said:
Hi all,

I have a simple circuit with a battery, resistor, and finally, the capacitor.

Am I correct in saying that adding additional resistors will increase the charging time, because adding resistors will decrease the overall current?

Thanks--
It is really far more fruitful to describe what happens using Maths.
We assume the three are in series. The time constant (time for the voltage across the Resistor to go to 1/e of any initial value) is given by RC. It's an Exponential variation. As the Voltage decreases exponentially, so does the current flowing because I = V/R.
 
A more direct way for you to consider the time constant is that RC is the time taken for the CURRENT in the series circuit to decrease to 1/e of its initial value.
(your question related to the current)
T = RC so larger R means longer time for the current to decrease.
Increasing R decreases the current which increases the time to charge the capacitor.
 
Last edited:

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