Current flow across inductors in Series

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Discussion Overview

The discussion revolves around the behavior of current flow across inductors in a circuit involving capacitors and inductors of varying inductance values. Participants explore questions related to the charging rates of capacitors, the role of inductors in energy storage, and the dynamics of current flow in the circuit.

Discussion Character

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

Main Points Raised

  • Some participants question whether the capacitors will charge at the same time given the different inductances in the circuit.
  • There is a suggestion that a mechanism exists to energize or de-energize the circuit, although it is not depicted in the diagram.
  • One participant notes that the upper capacitor will not charge at the same rate as the lower one due to the additional impedance from the smaller inductors in series.
  • Another participant raises the question of whether both inductors will store energy in their magnetic fields before the capacitors begin to charge, or if current flow will dictate the order of events.
  • There is a discussion about the factors that determine the time it takes for a steady current to flow through an inductor, with one participant seeking a formula for this calculation.
  • It is mentioned that in an ideal scenario, the current through an ideal inductor connected to a voltage source never reaches a steady value, but increases indefinitely unless a resistor is added to the circuit.
  • One participant refers to the concept of the time constant in RL circuits to explain how current approaches a steady value over time.

Areas of Agreement / Disagreement

Participants express differing views on the charging rates of the capacitors and the behavior of current in the circuit. There is no consensus on the exact dynamics of the circuit, and multiple competing perspectives are presented.

Contextual Notes

The discussion includes assumptions about the circuit's configuration and the ideal behavior of components, which may not fully account for real-world complexities. The lack of a clear depiction of the circuit and the unspecified energizing mechanism contribute to the uncertainty in the analysis.

Who May Find This Useful

This discussion may be of interest to individuals studying circuit theory, particularly those focused on the behavior of inductors and capacitors in electrical circuits.

Samson4
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I can't articulately ask the question so I drew a diagram. In the diagram, both capacitors are equal in capacitance. The bottom inductors are both 10000 nh and the top are 100 nh.
A. Will the capacitors charge at the same time?
B If we switch the large inductors to the top and the small to the bottom of the diagram, will the capacitors charge at the same rate?
 

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Can we assume that although it is not depicted, there exists some mechanism (a switch, possibly?) by which the circuit can be energized or de-energized at will?
 
While ever there is a changing current in an inductor there will be a voltage loss across that inductor. So, after switch-on, the upper capacitor won't charge at a rate exactly identical with that of the lower one because of the additional impedance in the upper ones path (the pair of tiny 100nH inductors).
 
brotherStefan said:
Can we assume that although it is not depicted, there exists some mechanism (a switch, possibly?) by which the circuit can be energized or de-energized at will?

Yes, I forgot to add it.
 
NascentOxygen said:
While ever there is a changing current in an inductor there will be a voltage loss across that inductor. So, after switch-on, the upper capacitor won't charge at a rate exactly identical with that of the lower one because of the additional impedance in the upper ones path (the pair of tiny 100nH inductors).

Okay, now this is what I thought. But, will both inductors store energy in their magnetic fields before either capacitor begins to charge? Or will it be a first come first serve deal with the current flow?
 
Samson4 said:
Okay, now this is what I thought. But, will both inductors store energy in their magnetic fields before either capacitor begins to charge?
The top capacitor charges as current flows to it via the top pair of inductors. Inductors store energy as current flows in them. The top pair of inductors are in series, so they share the same identical current, and their current is the current charging the top capacitor. So it all happens starting together.
 
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Okay, now what determines the time it takes for a steady current to flow through an inductor? Is there a formula I can look up?
 
Samson4 said:
Okay, now what determines the time it takes for a steady current to flow through an inductor? Is there a formula I can look up?
There is no steady current in the circuit depicted. Were you hoping there'd be a steady current somewhere? If so, why?
 
Oh i know that. I meant in general, knowing the parameters of an inductor, how can we calculate the time it takes before a steady current will flow through it.
 
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Analysis is generally not a simple matter, even where the inductor is assumed ideal. The simplest case would be where you have an ideal inductor connected across an ideal voltage source---and here the current never reaches a steady value, it just goes on increasing at a fixed rate forever. If you now insert a resistor in series with the inductor, to create a 3 element circuit, then after switch-on the current increases but with a decaying exponential. You might consider that after 5 or more time-constants have elapsed the current is getting close to a steady value.

If you are unfamiliar with these terms, google for RL circuit time constant.
 
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