Find impedance of a 2nd ODE circuit (PSPICE)

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Discussion Overview

The discussion revolves around calculating the impedance of a second-order differential equation (ODE) circuit using both PSPICE simulations and hand calculations. Participants explore the necessary equations and methods for determining impedance in the context of a lab report, while also addressing discrepancies in results obtained from different sources.

Discussion Character

  • Technical explanation
  • Homework-related
  • Debate/contested

Main Points Raised

  • One participant describes the circuit setup, including a sinusoidal AC voltage source and the need to calculate impedance using the formula Z = V/I, while expressing uncertainty about hand calculations.
  • Another participant provides the formulas for the impedances of inductors and capacitors, suggesting that these should be summed for a series circuit.
  • The original poster highlights discrepancies between their calculated results and those provided by lab instructors, indicating confusion over the calculations.
  • There is a suggestion to ensure that the exponents in calculations are expressed in radians rather than degrees, which may affect the results.

Areas of Agreement / Disagreement

Participants express differing views on the accuracy of their calculations and the results from the lab instructors. There is no consensus on the correct approach to resolve the discrepancies, and the discussion remains unresolved regarding the specific calculations.

Contextual Notes

Participants note potential issues with the accuracy of their results and the importance of using correct units in calculations. There is also mention of different results in lab notes compared to personal calculations, indicating a lack of clarity in the expected outcomes.

Evales
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See the circuit diagram attached.
The voltage source is a sinusoidal AC source with amplitude = 240, Frequency = 50, Phase = 90.

Essentially I have a lab report and I was wondering what sort of equations are required to find the impedance of the circuit. We're not really told if we're actually able to calculate this by hand (We've only just started 2nd ODE circuits)
The whole report is trying to prove that PSPICE produces correct answers.
See the probe diagram attached.

What our pspice instructions are, is to go the to second peak from the right of the probe and get the peak of the voltage over A [V(A)] and and go the the peak of the current over R1 [I(R1)], then using the values from those points and the phase difference substitute the values into:
Z = \frac{V}{I} to find the impedance.
So for my diagram I have:
Z = 239.931ej0/15.455e35.33j

I understand that these values are inaccurate (our lab sheet tells us this as well) however is there any way to do comparable hand calculations (not using the graph) that would give similar results?

I tried using S2+\frac{10}{300mH}S+\frac{1}{300mHx30uH}=0
To find the voltage at time t however when I used that value to get a current for the circuit I got a non complex number.

Any recommendations are much appreciated.

ALSO
Just realized that the lab notes (which have different results to mine, also known and okay) state that:
240e0xj/15.44e34.4xj= 12.9 - 8.8j
I'm totally not getting that when I plug it into my calculator.
I get: -15.35-2.44j

Anyone got any ideas?
 

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The impedances of inductors and capacitors are, respectively, ##j\omega L##, ##\frac{1}{j\omega C}##. Add up your impedances for a series circuit.
 
Thanks but you didn't respond regarding the discrepancy that I found in my lab instructors results. Please just tell me, I handed it in yesterday anyway.
 
Evales said:
Thanks but you didn't respond regarding the discrepancy that I found in my lab instructors results. Please just tell me, I handed it in yesterday anyway.

Make sure that the exponents of e in your calculations are expressed in radians, not degrees.
 

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