Finding i(t) (Source Free RL Circuit)

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  • Thread starter Thread starter salman213
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    Circuit Rl circuit
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Discussion Overview

The discussion focuses on finding the current i(t) in a source-free RL circuit, exploring the initial conditions and the mathematical formulation of the current over time. Participants engage in both theoretical and mathematical reasoning related to the circuit's behavior.

Discussion Character

  • Technical explanation, Mathematical reasoning

Main Points Raised

  • One participant presents the equation for a source-free RL circuit as i(t) = i(0)e^(-t)/T, where T is defined as L/Req.
  • The initial current i(0) is determined to be 5mA based on the inductor being shorted for t<0.
  • Another participant seeks clarification on the switch's position at t=0, confirming that it is closed for a long time before being opened at t=0.
  • Subsequent responses indicate agreement with the initial calculations and the approach taken to find Req.

Areas of Agreement / Disagreement

Participants generally agree on the initial conditions and the mathematical approach, with no significant disagreements noted in the responses.

Contextual Notes

There may be limitations in the assumptions regarding the circuit's behavior prior to t=0 and the definitions of the components involved, which are not fully explored in the discussion.

Who May Find This Useful

Individuals interested in circuit analysis, particularly in the context of RL circuits and transient responses, may find this discussion relevant.

salman213
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1. http://img529.imageshack.us/img529/6205/87421877rv5.jpg [/URL]3. First I found i(0)

the equation for a source free RL circuit is

i(t) = i(0)e^(-t)/T

T = L/ReqSince the inductor will be shorted when t<0, i(0) must be 5mA.

Now to find Req I added series and parallel appropriately to find

Req = 3/4k Ohms

so my equation is

i(t)= (5x10^-3)e^(-t)/T
where T = (1x10^-3)/(3/4x10^3)can someone please check that, Thanks!
 
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By that arrow pointing to t=0, do you mean that the switch is closed for a very long time for t<0 and is opened at t=0?
 
ya for a very long time (t<0) the switch is "horizontal" then at t=0 it is moved to the lower point.
 
Yeah I got the same answer.
 
ok great, thanks!
 

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