Find RLC Values in RLC Series Circuit

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SUMMARY

The discussion focuses on determining the resistance (R), inductance (L), and capacitance (C) values in an RLC series circuit using the given current function i(t) = (125/24) * exp(-700t) * Sin(2400t) mA. The Laplace transformation of the current is identified as I(s) = 12500/[(s+700)^2 + 2400^2]. Participants highlight the discrepancy between this transformation and the one derived from Kirchhoff's Law, which results in I(s) = 1/[s*(LC*s^2 + RC*s + 1)], noting the difference in polynomial degrees in the denominators. The conversation emphasizes the need for clarity in applying Laplace transformations and solving differential equations to find the circuit parameters.

PREREQUISITES
  • Understanding of RLC circuits and their behavior.
  • Familiarity with Laplace transformations and their applications in circuit analysis.
  • Knowledge of Kirchhoff's Laws for electrical circuits.
  • Ability to solve differential equations related to electrical circuits.
NEXT STEPS
  • Study the application of Laplace transformations in RLC circuit analysis.
  • Learn how to derive and solve differential equations for RLC circuits.
  • Explore the relationship between current and voltage in RLC circuits using Kirchhoff's Laws.
  • Investigate the implications of polynomial degree differences in Laplace-transformed equations.
USEFUL FOR

Electrical engineers, circuit designers, and students studying circuit theory who need to analyze RLC circuits and apply Laplace transformations for circuit parameter determination.

danilorj
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Guys,
Let's suppose we have RLC series circuit feeded by tension source initially with no energy stored. When we apply an unitary step of tension at t=0 at the terminals of the circuit, we observe a current of i(t)=(125/24) * exp(-700t)* Sin(2400t) mA that goes around the circuit for t>0s.
I want to find the values of R, L, C.
I was trying to match the laplace transformation of the current above to the laplace transformation of the circuit for the current but no success.
 
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danilorj said:
Guys,
Let's suppose we have RLC series circuit feeded by tension source initially with no energy stored. When we apply an unitary step of tension at t=0 at the terminals of the circuit, we observe a current of i(t)=(125/24) * exp(-700t)* Sin(2400t) mA that goes around the circuit for t>0s.
I want to find the values of R, L, C.
I was trying to match the laplace transformation of the current above to the laplace transformation of the circuit for the current but no success.

Can you just write the differential equation for the current and voltage of the circuit, solve the DE and apply your initial conditions? That should get you the answer as well. Or are you required to use transforms?
 
Let me explain it better
The Laplace transformation of the given current is I(s)=12500/[(s+700)^2+2400^2]
And if I apply the Kirchhoff Law Tension around the RLC series circuit I get
I(s)=1/[s*(LC*s^2+RC*s+1)]. But I don't know what to do with this. They seem to be different, one has degree 3 and the other has degree 2 in the denominator.
 
And I think the best way of doing this is using the Laplace transformation, cause solving the differential equation would take a very hard work, and I don't think it's going to work as well.
 
danilorj said:
Let me explain it better
The Laplace transformation of the given current is I(s)=12500/[(s+700)^2+2400^2]
And if I apply the Kirchhoff Law Tension around the RLC series circuit I get
I(s)=1/[s*(LC*s^2+RC*s+1)].
Show us how you got this. I don't think it's correct, which is why it's not matching up with the I(s) you were given.
But I don't know what to do with this. They seem to be different, one has degree 3 and the other has degree 2 in the denominator.
 

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