Impedance Definition and 507 Threads

In electrical engineering, electrical impedance is the measure of the opposition that a circuit presents to a current when a voltage is applied.
Quantitatively, the impedance of a two-terminal circuit element is the ratio of the complex representation of the sinusoidal voltage between its terminals, to the complex representation of the current flowing through it. In general, it depends upon the frequency of the sinusoidal voltage.
Impedance extends the concept of resistance to alternating current (AC) circuits, and possesses both magnitude and phase, unlike resistance, which has only magnitude.
Impedance is a complex number, with the same units as resistance, for which the SI unit is the ohm (Ω).
Its symbol is usually Z, and it may be represented by writing its magnitude and phase in the polar form |Z|∠θ. However, cartesian complex number representation is often more powerful for circuit analysis purposes.
The notion of impedance is useful for performing AC analysis of electrical networks, because it allows relating sinusoidal voltages and currents by a simple linear law.
In multiple port networks, the two-terminal definition of impedance is inadequate, but the complex voltages at the ports and the currents flowing through them are still linearly related by the impedance matrix.The reciprocal of impedance is admittance, whose SI unit is the siemens, formerly called mho.
Instruments used to measure the electrical impedance are called impedance analyzers.

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  1. electrogeek

    Interpreting electrochemical impedance spectroscopy (EIS) circuits

    Hi all, I'm fairly new to electrochemical impedance spectroscopy (EIS). On some slides I was given, I have been provided with two circuits which would produce the same nyquist plot. I was wondering what real-world scenario these circuits would relate to. I know that the left-most resistor in...
  2. Tesla In Person

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    For a parallel RLC circuit, I have found the complex impedance to be 1/ (1/R -j(1/wL +wC)) . I need to find the phase difference between the voltage and current in the circuit. I know it's given by tan^-1(im(z)/re(z)) but how do I do it here as the expression is a fraction?
  3. Olha

    A From Nyquist plot to real conductivity spectra (sigma)

    Hi, I have data of impedance but due to limitation of software after measurement I do not receive numerical values for admittance and real conductivity vs frequency. How mathematically I can convert Nyquist plot into plot real conductivity vs frequency?
  4. DIYEngine235

    Amplifier Circuit help, impedance matching

    I've been working on a personal project to connect my old H10 series david-clark headset to my UV-5R radio. Up to this point, I've been using the headset purely as a set of headphones to listen in, but I want to be able to transmit with it as well. The problem I'm running into is that the...
  5. S

    800 ohm transmission line from Ethernet cable?

    If the 8 pairs in a CAT-5 LAN cable are wired as shown so that their impedances add up, will it work well as an 800 ohm line up to around 30 MHz? .... Or, would I have to slit the plastic sheath and put some separation between the pairs?
  6. AlexB23

    I Planck's Impedance: Exploring the Mystery of a Fictional Measurement System

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  7. P

    Integrate or divide the input impedance for transmission lines in series?

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  8. gasgas

    Ring Impedance & String Connection: Is It Valid?

    If we consider the coefficient b as the rings impedance, we can consider the effective impedance on the right to be b+Z2 where Z2 is the impedance of the second string. Then because there is no reflection it follows that Z1=b+Z2 or b=Z1-Z2. Is this a valid solution? My professor went through a...
  9. N

    Calculating Input/Output Impedance w/ Parallel Resistors

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  10. S

    Power Amplifier and Exciter, Impedance / Power

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  11. X

    Impedance of a half-wave dipole antenna

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  12. N

    Finding theoretical impedance of acoustic transducer

    Hi all If we have an acoustic transducer and values of its two parameters are known, i.e conductance and capacitance, is it possible to calculate impedance using these two parameters? Thanks
  13. N

    Impedance mismatch issue in receivers

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  14. A

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  15. Joshy

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  16. iochoa2016

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  17. mechorigin

    Engineering Having issues series resistive and reactive impedance matching

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  18. A

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  19. T

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  20. D

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  21. R

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  22. T

    Impedance Matching when the Transmitter, Line and Load impedances are different

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  23. brainbaby

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  24. P

    Engineering Finding out the input impedance in a negative feedback op-amp

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  25. P

    Engineering Analyzing the output impedance and open loop gain of a IC-741 Op-Amp

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  26. T

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  27. J

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  28. Andrei0408

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  29. R

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  30. J

    Calculate the impedance in this RC circuit

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  31. duchuy

    Magnetic permeability and optical impedance

    Hi, It's given that an electromagnetic wave (5.10^14 Hz) traveling in an environment with the index n = 1,33, where the magnetic permeability (μ) is equal to the magnetic permeability in a vacuum (μ0). The optical impedance (Z) is given by the formula : Z = μ . c/n. I tried to turn μ into μ0 to...
  32. C

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  33. J

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  34. Maverickans

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  35. B

    Engineering RLC Series Network: Impedance, Current, Power Factor, Phasor Diagram

    Hello. I have completed the following question. My answer: i) Circuit Impedance Reactance = XL = 2 x pi x F x L = 2 x pi x 50 x 0.15 = 47.12 Ohms Reactance of Capacitor = XC = 1/2 x pi x F x C...
  36. I

    Impedance of Circuit (Complex Numbers Question)

    Question is from Boas Ch. 2 Q.41 (I've the first edition) or Q 16.8 in the 3rd edition. Find the impedance of the circuit shown (R and L in series, then C in parallel with them). Circuit is essentially this (it is a closed circuit which I can't easily draw). -----R------L--- -------C---------...
  37. putrinh

    How to solve this to calculate the input impedance?

    How did you find PF?: Google search I got a problem, how to calculate this formula from euler to imajiner? or how calculate this case?
  38. tanaygupta2000

    What is the effect of feedback on input and output impedances?

    I know that when the feedback is connected, the voltage gain changes by the above formula. But I don't know how to find final values of input and output impedances.
  39. AA6EG

    Feedline impedance matching for the WSM 50 Kilowatt AM station in Nashville TN

    The WSM 50 Kilowatt AM station in Nashville TN, has been transmitting using the same ~950ft 5/8 wave Blaw Knox Diamond antenna, since 1929. The 5/8 wave vertical had some horizon gain over a 1/4 wave vertical so theoretically will serve distant listeners better. It was found though that...
  40. brainbaby

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    Hello friends, I am studying an article on impedance matching which states about matching a resistance of 52 ohms with 2k ohm. It is accomplished by adding an inductance of XL= 318 ohms in series with the 52 ohm resistor yielding a parallel equivalent of 328ohm as reactance and 2k ohm as my...
  41. paulmdrdo

    Finding the output impedance of Current Controlled Current Source

    Summary:: I was trying to derive the equation for the output impedance of the ICIS circuit. Here's what I've tried so far. What I have derived does not agree with the one provided in my book. Since it is a current source the negative feedback must increase the output impedance. The one I...
  42. E

    Help with Homework Equation: Input Impedance

    Homework Equation: I do not think I am getting the correct answer for this problem when I do it out by hand. Do I plug the necessary values into the equation shown above or do I say that because it is an infinite line that the characteristic impedance is equal to the input impedance? If the...
  43. E

    Characteristic Impedance of a coaxial cable

    Image 1: Image 2: I am attempting to learn about transmission lines and am having problems with this homework problem. For part a, I have derived an equation for the maximum electric field within the dielectric. I came up with: with r being the radius and the electric field decreasing with...
  44. R

    Best way to match impedance between an amplifier and transducers

    I am trying to figure out the best way to match impedance values between an amplifier (50 Ohm) which powers a number of transducers (initially 50 Ohm but could change). For one transducer I have previously used a step up transformer (SUT) device between the amplifier and transducer. Now I have...
  45. brainbaby

    How does the tapped capacitor network increase the impedance?

    Please help me comprehend the text below... The discussion begins with the current flowing through the inductor for both the cases (case a and b) stays same.The input voltage is Vi. When two tapped cap is used with the current that is flowing in the inductor is divided among the two capacitor...
  46. brainbaby

    Determine the output impedance of the circuit

    Hi friends, I have taken three sine AC sources and have joined them in series. I want to find the output impedance of this circuit. Formula that I am using is...Output impedance = (Open circuit voltage - Output voltage with load R1) / Output current with load (R1) Load resistance = 1 k ohm...
  47. J

    Engineering Input and Output Impedance of an Opamp Circuit

    I know for ideal opamp the input Z is infinite, and output Z is 0, but not sure about this opamp.
  48. M

    Calculate the zero-sequence line impedance

    Hi. I want to calculate sequence line impedance of transmission line. But i can't find any parameter of Z1 and Z0 of transmission line in simulink. It's only have parameter about number of phase, frequency, R1/R0, L1/L0, C1/C0 and line length. Can i calculate sequence line impedance from these...
  49. DamunaTaliffato

    What are the mistakes in determining output impedance using h-parameter model?

    I have this curcuit. I want to discover the output impedance. Using h-parameter model I get the second circuit. I know that Zout= V(open circuit)/I(short circuit) and ie = C ib, where C is an appropriate proportionality factor. Vol = V1 Re/(Rb+Re) = (Rb ib + Re ie) Re/(Rb+Re) Isc = ie = C ib...
  50. Pierson5

    Complex impedance and phase angle of a circuit

    I've attached my work below. The numbers seem odd to me though. Are my equations correct? Is the phase angle really (0/12)? If so, what are the implications of that?
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