Boundary conditions for a purely inductive load in an AC circuit

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Discussion Overview

The discussion revolves around the boundary conditions for a purely inductive load in an AC circuit, specifically focusing on the integration of Kirchhoff's equation and the implications of the constant of integration in the context of alternating current. Participants explore the physical meaning of this constant and its dependence on initial conditions, as well as the justification for its value in relation to the periodic nature of the emf.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants express confusion about the arbitrary constant \( c \) in the integration of Kirchhoff's equation, questioning its physical significance and how it should be determined.
  • Others argue that the value of \( c \) is dependent on initial conditions, specifically the current at time \( t = 0 \), but they struggle to define what "initial" means in the context of a periodic function.
  • A participant suggests that the current intensity is maximum at certain points in the cycle, but questions the justification for this observation, feeling it is based on hindsight.
  • Some contributions highlight that the mathematical treatment allows for a non-zero \( c \), but they seek a physical rationale for why it is often dropped in standard solutions.
  • A later reply proposes a scenario involving a battery and resistor in series with an inductor to illustrate how initial conditions can be set, but this leads to further questions about the current before applying the sinusoidal voltage.
  • Participants discuss the implications of the rotating coil in a magnetic field and how it relates to the periodic nature of the emf, with some emphasizing the need for a clear understanding of the initial conditions affecting \( c \).

Areas of Agreement / Disagreement

Participants generally agree that the value of \( c \) is determined by initial conditions, but there is no consensus on how to define these conditions in the context of a purely inductive load and its periodic nature. The discussion remains unresolved with multiple competing views on the justification for the constant.

Contextual Notes

Limitations include the ambiguity surrounding the definition of "initial" in a periodic context, the lack of clarity on how to derive the value of \( c \) from physical principles, and the absence of a consensus on the implications of dropping the constant in standard solutions.

  • #31
FranzDiCoccio said:
Uhm. Right, but the standard derivation of a purely inductive circuit never mentions any resistor, and
<br /> I(0) = \frac{V_0}{\omega L}<br />
It seems hard to make contact with your answer.
The resistor is there just to set up the initial condition. When you apply your voltage ##V_0 sin(\omega t) ## it no longer forms any part of the inductor current.

You have set up an initial current and have then applied your voltage directly across the inductor.
 

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