Need help on solving a RL circuit with switch

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Discussion Overview

The discussion revolves around solving a RL circuit with a switch, specifically finding the voltage v(t) for times before and after the switch operation. Participants are attempting to understand the behavior of the circuit at t=0 and the implications of the switch's position on the circuit's current and voltage.

Discussion Character

  • Homework-related
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant expresses confusion over the calculated current through the inductor and the resulting voltage across a resistor, noting a discrepancy with the textbook answer.
  • Another participant questions the meaning of I_o and suggests it should be calculated at t=0-.
  • A participant seeks clarification on the circuit configuration, specifically regarding the flow of current through different branches at t=0.
  • There is a discussion about the nature of the controlled source in the circuit, with one participant asserting it is a voltage source based on its notation.
  • Participants note the significance of symbols in the circuit diagram, such as the little o symbol below the current arrow, indicating potential confusion over notation.

Areas of Agreement / Disagreement

Participants do not appear to reach a consensus on the correct interpretation of the circuit behavior or the calculations involved. Multiple viewpoints and interpretations remain present.

Contextual Notes

Participants express uncertainty regarding the initial conditions and the implications of the switch's position on the circuit's behavior. There are unresolved questions about the calculations and the significance of certain symbols in the circuit diagram.

Who May Find This Useful

Students and individuals studying electrical circuits, particularly those focusing on RL circuits and switch operations.

madcowdisease
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Homework Statement


tLfeD.jpg



Homework Equations


Find v(t) for t < 0 and t > 0 in the circuit.


The Attempt at a Solution


I tried to find the i through the inductor for both t=0- and t=infinity, but I did not get the same result as the answer given in the txtbook which is 96e-4t V. According to the answer given from the txtbk, if I'm not wrong, i(t) shud be i(t)=48e-4t A, and then to find v at the 2 ohm resistor, i(t) X 2 and u get v(t).

I do not really understand why, I've been on this qn for 1 hr and stil can't understand it.
Please help and thank you.
 
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madcowdisease said:

Homework Statement


tLfeD.jpg



Homework Equations


Find v(t) for t < 0 and t > 0 in the circuit.


The Attempt at a Solution


I tried to find the i through the inductor for both t=0- and t=infinity, but I did not get the same result as the answer given in the txtbook which is 96e-4t V. According to the answer given from the txtbk, if I'm not wrong, i(t) shud be i(t)=48e-4t A, and then to find v at the 2 ohm resistor, i(t) X 2 and u get v(t).

I do not really understand why, I've been on this qn for 1 hr and stil can't understand it.
Please help and thank you.

What's I_o?
 
Io is I0, the value should be calculated when t=o-
 
madcowdisease said:
Io is I0, the value should be calculated when t=o-

It's a bit confusing for me, but to clarify... So the switch is opened at t=0? And right before then, there is 1*I_o flowing to the left, and 3*I_o flowing to the right? To add up to the 4*I_o that is supplied by the dependent current source in the middle?
 
I think the idea is that at t=0, the 3-ohm branch is disconnected and the 8-ohm branch is connected. The controlled source is a voltage source since it has the + and - signs in it, not an arrow.

I noticed there's a little o symbol right below the arrow for current i. Is that significant?
 

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