Solving Transient Response RL Circuit with Switch

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Discussion Overview

The discussion revolves around solving a transient response problem in an RL circuit that includes a switch, inductor, resistors, and a diode. Participants explore the behavior of the circuit when the switch is open and closed, addressing various parts of a homework question related to the circuit's operation and current flow.

Discussion Character

  • Homework-related
  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant initially calculates the time constant and steady state inductor current but expresses confusion about the circuit's behavior when the switch is open and closed.
  • Another participant explains the sequence of events when the switch is closed and then opened, detailing how the inductor current behaves and its implications for subsequent parts of the homework.
  • A later reply suggests that part (c) of the question is misleading and clarifies that the current through the diode is only -10 mA if the switch remains open for an extended period.
  • Further comments indicate that part (d) is crucial for understanding part (e), while part (f) presents additional challenges due to the diode current not reaching zero.

Areas of Agreement / Disagreement

Participants express varying levels of understanding and interpretation of the circuit's behavior, with some clarifications provided but no consensus reached on all aspects of the problem.

Contextual Notes

Some assumptions about the circuit's operation and the definitions of terms may be missing, and the discussion does not resolve all mathematical steps or implications of the circuit behavior.

Who May Find This Useful

Students working on RL circuits, particularly those dealing with transient responses and switch operations, may find this discussion relevant.

van123
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Homework Statement


I have a circuit containing an inductor, 2 resistors and diode in series however there is also a switch.




The Attempt at a Solution



I thought that when the switch is closed there would be no current flowing through the right side of the circuit (resistor and diode) and therefore for part a) the time constant is L/R=10/20=0.5ms and steady state inductor current is just V/R=0.5A.
However, this can't be the case in order to do the show that question in part C), so I was wondering if someone could just explain the circuit to me when the switch is open and closed. Thank you!
 

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What, in toto, is the question?
Never mind, I got the picture straightened out. Stand by ...
 
Last edited:
How it works: at t=0 swirch S is closed and the current thru the inductor increases. At t = 0.5ms S opens and the inductor current continues thru the diode until iL = 0 at t = TZ. The current stays at zero until S closes again, at which point the cycle repeats.

How about doing (b)?

Part (c) is misleadingly stated. The current thru the diode is -10 mA only if the switch stays open for a long time.

(d) is an important computation. You will need it for part (e).

Part (f) is more challenging because the current thru the diode does not ever equal zero.
 
Reattempt

Thank you rude man so much for explaining, i have tried to answer the entire question again from what I (hope) i now understand. If you have time could you perhaps see my answers and tell me if I'm still not getting it?
Thanks again!
 
van123 said:
Thank you rude man so much for explaining, i have tried to answer the entire question again from what I (hope) i now understand. If you have time could you perhaps see my answers and tell me if I'm still not getting it?
Thanks again!

Certainly. I await your submission.
 

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