Impedances of R, L, C, RL, RC, LC and RLC circuits

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SUMMARY

The discussion focuses on calculating the impedance (Z) of various electrical circuits involving resistors (R), inductors (L), and capacitors (C). The key equations derived include Z = R for resistors, Z = R + i(ωL - (ωC)⁻¹) for series circuits, and Z = (Z1⁻¹ + Z2⁻¹ + ...)⁻¹ for parallel circuits. The importance of complex numbers in these calculations is emphasized, particularly the relationship j² = -1. Participants are encouraged to derive specific impedance values for given configurations.

PREREQUISITES
  • Understanding of basic electrical circuit theory
  • Familiarity with complex numbers and their operations
  • Knowledge of series and parallel circuit configurations
  • Basic principles of AC circuit analysis
NEXT STEPS
  • Study the derivation of impedance in RLC circuits
  • Learn about phasor representation in AC circuit analysis
  • Explore the use of MATLAB for simulating RLC circuits
  • Investigate the impact of frequency on impedance in RL and RC circuits
USEFUL FOR

Electrical engineering students, circuit designers, and anyone involved in analyzing or designing RLC circuits will benefit from this discussion.

Bruno Tolentino
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Homework Statement


In first place, ignore the source in each circuit, ignore if make sense or not. I placed one sorce in each circuit just for the circuit be more visible.

In second place, ignore the numerical values of the sources, resistors, capacitors and inductors. Think R, L and C in place of numerical values.

So, my doubt is the following: given all these circuits, what is the equation of the impedeance (Z) in function of R, L and C?

01.png


02.png


03.png


Homework Equations

The Attempt at a Solution



1.1) Z = R
1.2)
1.3)

2.1)
2.2)
2.3)
2.4)
2.5)
2.6)

3.1) Z = R + i(ωL - (ωC)⁻¹)
3.2) Z = R⁻¹ + i(ωC - (ωL)⁻¹)
3.3)
3.4)
3.5)
3.6)
3.7)
3.8)
 
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ZR = R
ZL = jωL
ZC = 1 / jωC = j / (j*j*ωC) = -j / ωC

In series you just add the impedances.
In parallel use: Z = ( Z1-1 + Z2-1 + . . . )-1

You must be able to calculate with complex numbers. Just remember that j2 = -1.

Try to calculate 3.1) and 3.2) yourself ( think you have read the answer somewhere ).
 
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