Understanding Capacitor and Inductor Behavior: A Physically-Based Explanation

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    Capacitor Inductors
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Discussion Overview

The discussion focuses on the behavior of capacitors and inductors, specifically addressing why the voltage across a capacitor does not change immediately and why the current in an inductor also does not change instantaneously. The scope includes conceptual explanations and technical reasoning related to electrical components in circuits.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant asks for a physical explanation of the delayed voltage change in capacitors and current change in inductors.
  • Another participant explains that the voltage on a capacitor is dependent on the accumulation of electric charge, which takes time and work.
  • A different participant presents mathematical relationships for capacitors and inductors, suggesting that if the time interval is infinitesimally small, the resulting changes in voltage and current would theoretically become infinite.
  • This participant also notes a practical observation regarding inductors, stating that when a DC current is switched off, the inductor can produce a spark to maintain current flow.
  • One participant directs others to a related thread for further reading on inductors and invites follow-up questions about capacitors.

Areas of Agreement / Disagreement

Participants express various viewpoints and explanations regarding the behavior of capacitors and inductors, but no consensus is reached on the specific mechanisms or implications of these behaviors.

Contextual Notes

Some assumptions about the ideal behavior of capacitors and inductors may not be fully addressed, and the discussion includes references to practical observations that may depend on specific circuit conditions.

Passionate Eng
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Physically, can someone explain why does not the voltage on the capacitor change immediatly?
and why does not the current in the inductor also do?
:smile:
 
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The voltage on the capacitor is a function of the amount of electric charge on its two plates. It takes time, and work, for the charge to accumulate.
 
As for the capacitor:

I = C * dV/dt

So if dt is infinite small, dV/dt and thus I will become infinite high.

As for the inductor:

V = L * dI/dt

So if dt is infinite small, dI/dt and thus V will become infinite high.
Practically, if you feed an inductor by a DC-current and switch it off, the inductor will immediately produce a (long) spark, thereby keeping up the current.
 

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