Impedance Definition and 507 Threads

  1. J

    How do I calculate impedance for different components at a specific frequency?

    Calculating Impedance Help! Homework Statement calcuate the impedance at the frequency 10Hz of a: -4.7 kil0 ohm resistor -1microFarad capacitor -25mH inductor Homework Equations w=2*Pi*f The Attempt at a Solution for the capacitor impedance= 1/20*Pi*1*10^-6 for the...
  2. Z

    How to measure the output impedance of this cct

    hi i want to find the output impedance of the following cct so i can perform pi matching on it but i don't know how to find it using lt spice please help! added schematic
  3. B

    Calculate the total impedance of the circuit

    Homework Statement Consider a circuit, composed of a resistance R and an inductance L in series with an AC generator providing a voltage V(t)=V(subscript 0) cos (omega*t) calculate the total impedance of the circuit, and the phase difference between its resistive and inductive components...
  4. L

    Antenna and Freespace Impedance

    Why isn't the antenna impedance (usually 50 ohms) matched with free space impedance (377 ohms)? Won't the mismatch result in some loss.
  5. P

    Constraint on Thevenin impedance

    Let's say we have a circuit composed of simple linear circuit elements (resistors, inductors and capacitors). Now we calculate the Thevenin equivalent circuit for some load within this circuit, and we determine the Thevenin impedance, Z_t. My question is this: Is it generally the case that...
  6. joema

    Polar coordinates of complex impedance

    The question is: "In polar coordinates, what is the impedance of a circuit that has an admittance of 7.09 millisiemens at 45 degrees?" The official answer is: "141 ohms at an angle of -45 degrees". I don't understand this. 7.09 millisiemens is 141 ohms, and the positive phase angle...
  7. P

    Finding Input/Output Impedance of a CE Amplifier: Practical Methods

    how can i find input and output impedance of a ce amplifier- (voltage divider )..suggest practical methods?
  8. N

    Determine Reflection Coefficient & Load Impedance: Slotted Line 150ohms

    A slotted line used on a 150ohm lossless transmission line connected to an unknown load impedance, ZL. The voltage standing wave ration is found to be equal to 3. The distance of the first voltage maximum from the load is found to be 9 cm, and the first voltage minimum is located at 3 cm from...
  9. D

    Impedance matching for audio amp

    Will an audio amp burn up if the speaker connected to it has a lower impedance than the amp's output impedance?
  10. A

    Getting time domain current from impedance and voltage measurement?

    I'm working on a high power multi-phase DC/DC converter where the load current has some fast transients. We can easily measure the output voltage in the time domain, and also measure the power distribution network impedance in the frequency domain. So, I think I would try converting the...
  11. F

    6 part 2 loop RLC circuit complex impedance

    Homework Statement I'm trying to determine this insane circuit's |Z| so I can use an AC voltage to find the current as a function of time. This is my circuit (the switch is closed, and ignore the values): http://i.imgur.com/mA55I.png Homework Equations Impedances for each of the RLC...
  12. B

    What is the Impedance of a Plane Wave Passing Through a Metal?

    Homework Statement A plane wave is passing through a metal. Show that the impedance Z can be given by Z = \sqrt{ \frac{2 \omega \epsilon _0} {\sigma} } \frac{Z_0}{1-i} where Zo is the impedance of free space and sigma is the conductivity. You may assume that E is polarised in the x...
  13. PainterGuy

    Input Impedance Explained: Example 1-5 Analysis

    Hi, :smile: Please have a see Example 1-5 on the given link: http://img854.imageshack.us/img854/8376/inputimpedance.jpg The example mentions input impedance. What is it in simple words? The book says: Because this input impedance is across the measured terminals , a small current flows...
  14. D

    Whats all this impedance stuff anyhow?

    Okay, so my short experience in radio has taught me that the input and output of every RF system is designed around some certain impedance. Typically 50 ohms or 75 or 300... So you take a transmitter and hook it to a tuned antenna with some sort of feedline like coax. The coax is the same...
  15. I

    Understanding Parallel Impedance

    Hi everyone, I seem to be having a little trouble with parallel impedance. I have the equations, but I don't understand why, I am not asking for a super proof, just an explanation. So basically we have a circuit of: ac source, then a capacitor and resistor in parallel. the formula...
  16. W

    Impedance in an electric Circuit

    Homework Statement Homework Equations V=IR ? The Attempt at a Solution My main problem with this question is that impedance seems to apply only when inductors and capacitors are involved, but this circuit includes only resistors, so it seems to me like I could just treat it as resistance...
  17. L

    Calculating Impedance in an RLC circuit

    Homework Statement Calculate the impedance Zab across ab. w=0.75 Hz wo=1 Hz. L=1 H R=1 Ohm C=1 F Inductor and Capacitor are in series, and together are in parallel with the resistor. circuit looks like a capital A, but square on top, and rotated 90 degrees clockwise.. if that...
  18. D

    Engineering Finding total impedance of the circuit

    Homework Statement here is the circuit I am trying to figure out Homework Equations I have to find the total impedance for the circuit. The Attempt at a Solution I know how to find the total impedance in a series circuit and in a parallel circuit when I have just the Resistor...
  19. C

    Equivalent Impedance: Find Z=84.907-j20.12 ohms

    Homework Statement Find the input impedance Z. (i.e. Find Z equivalent.) Answer in the back of the book: Z=84.907-j20.12 ohms [PLAIN]http://img834.imageshack.us/img834/8508/circuit.png Homework Equations n/a ** j=sqrt(-1) The Attempt at a Solution I combined the 60-ohm, 50-ohm, and...
  20. F

    How to Calculate Inductance Using a General Impedance Converter?

    http://img146.imageshack.us/img146/9356/capturexh.jpg Attempt at Solution: Well I put R1 and C1 in my RCL circuit, and then used the GIC rules to calculate the "L" inductance for the remainder of the circuit using R2,R3,R4,R5, and C2. So I did X = (Z1*Z3*Z5)/(Z2*Z4) where Z1=R2, Z2...
  21. D

    Output impedance of a Pass Transistor

    Homework Statement Calculate the output impedance of the emitter-follower circuit called a pass transistor. Assume that beta=200 **See attached diagram** Homework Equations The Attempt at a Solution Not really sure how this works, I thought it would just be 1k cause that is the...
  22. Simfish

    Is there a way to test the total impedance of my body?

    I'm just really curious about where I'd fit in this chart: http://en.wikipedia.org/wiki/Electric_shock#Pathophysiology
  23. P

    Mechanical impedance at ends of bar

    Assuming very small losses, find a condition relating the mechanical impedances of the supports at the ends of a bar of length L and longitudinal wave speed c if the bar is to have an integral number of wavelengths between its ends when it is vibrating longitudinally. mechanical impedance...
  24. 1

    Transmission zeros of driving point impedance functions

    Hello all, This question might be at the same time both general and very specific. Admittedly, it has been over 10 years since I really thought about circuit analysis, but I hope I might get some help here! So, thanks in advance! I will ask a few questions here to make the presentation...
  25. Z

    How Does Capacitance Affect Current Amplitude in a Shunted RLC Circuit?

    Homework Statement An emf Vosinwt is applied to a circuit which consists of a self inductance L of negligible resistance in series with a variable capacitor C. The capacitor is shunted by a variable resistance R. Find the value of C for which the amplitude of the current independent of R...
  26. M

    Why Do We Treat Input and Output Impedances Differently in FET Amplifiers?

    Hi guys, can anyone tell me the reason why we set Vi=0 (short circuit the input side) when we want to find the output impedance Zo but we don't do the same by setting Vo=0 when we find the input impedance Zi? and why do we let Io=0 (open circuit the output side) to find the gain Av? thank you
  27. T

    Specific Acoustic Impedance of Standing Wave

    Homework Statement Find the specific acoustic impedance for a standing wave p=Psin(kx)exp(jwt) where p is a complex variable.Homework Equations z = p/u (all variables are complex) u = (A/rho_sub_0*c)*exp^(wt-kx)The Attempt at a Solution Approaching this problem it seems that I have all of the...
  28. M

    Calculating Impedance and Drawing a Basic Phasor Diagram

    Homework Statement I have attached the problem and all my work. If someone can check my work for part a, that would be great. As far as part b, I need the most help here. Finally for part c, I think my work so far is correct, but I need help to graph it. Thank you in advance. Homework...
  29. Simfish

    Impedance across AC voltage source

    Homework Statement An impedance 1000(1 + i) Ω (and note it contains an imaginary part) is connected across an AC voltage source of amplitude 10 V and frequency 60 Hz. Whatʼs the power dissipated during one cycle within the impedance? Homework Equations P = Re(V*I), where V* is complex...
  30. A

    Calculating L to Make Net Impedance Resistive at a Certian Freq.

    Homework Statement The circuit is a resistor (200 ohms) and a capacitor (200 nF) in series, and that is in parallel with an inductor. Homework Equations [tex]$Z=j \omega L$[\tex] [Gah, how do I make the latex render?] The Attempt at a Solution I'm not really sure where to start with this...
  31. K

    What is the conjugate impedance of 30+j40?

    Urgent! About Impedance the total ohm of this impedance ( 30+j40 ) is 50ohm. but wat is the conjugate impedance ?? 30-j40? total ohm is wat? 30+j40 is 50ohm solution is square root of (302+402)
  32. ?

    Solving Complex Impedance Homework Q2

    Homework Statement Question 2 on this paper: http://www.eng.cam.ac.uk/teaching/past_papers/examples_student/examples_IA/P3_LCD_Q/1ap3lcdq003 Homework Equations Z = V/I V=L di/dt The Attempt at a Solution for part a of the question: I began with V = Vo cos(wt) And I = Io cos (wt + k) I...
  33. E

    Complex impedance and negative reactance

    Homework Statement consider a circuit expressed by v(t)= 100cos \omega t and i(t)=2cos(\omega t+\pi / 3) . Find the reactance.Homework Equations Z=\frac{V}{I} = R+jXThe Attempt at a Solution Z=\frac{100}{2\angle \pi /3} = 50\angle -\pi /3 = 46 - j19 Does the negative imaginary part mean...
  34. E

    Engineering Total Impedance of RL Circuit in Parallel with Resistor

    Homework Statement find total impedance of a circuit with R1 and L in parallel with R2. circuit looks like this (but with R2 instead of C): http://wpcontent.answcdn.com/wikipedia/en/thumb/7/75/RL_series_C_parallel.svg/160px-RL_series_C_parallel.svg.png Homework Equations formula for two...
  35. E

    Engineering Complex impedance of parallel RC circuit

    In my book (Storey), there's an exercise with a parallel RC circuit, where R = 80 Ohm and C = 30 uF. The answer for the complex impedance is supposed to be 40-j40, however I can't seem to get there! I've showed my working under. Am I doing something wrong, or is the book's answer wrong? (freq...
  36. H

    OP Amp Input Impedance Explained

    Hello Am reading about amplifiers, and the articles i read suggests that for a successfull amplification the op amp should have an input impedance and zero output impedance. I want some explanation about this information, why the input and output impedance are important factors?
  37. R

    Modeling Input Impedance of MESFET Using Series RLC Circuit

    Hi, I'm trying to model the input impedance of a MESFET by using a series RLC circuit. For example I have the following reflection coefficients: .575 angle(-138) at 6 GHz .617 angle(170) at 8 GHz .610 angle(128) at 10 GHz As you can see, as the frequency changes so too does the angle. Does...
  38. R

    RLC Series/Parallel Impedance Near Resonance

    Hey, The impedance of the series and parallel RLC circuit both tend to R near the resonant frequency (one is a min/ one is a max) so if I expand the frequency around this point I should be able to show they are the same for \delta \omega small right? For some reason I can't get it to work. Any...
  39. J

    Impedance of a parallel RC circuit?

    Hi there, I have a circuit in which consists of a resistance (rs) in series with parallel combination of capacitor and resistance(rc). I want to calculate value of rs. So i did this by calculating total impedance Ztotal which is V/I and then substracting impedance of parallel rc circuit...
  40. S

    Physics underpinning Impedance Plethysmography

    I'm looking for references or some place where i can find the calculations that impedance plethysmography is based on.
  41. S

    Impedance matching vs max power transfer criterion

    Hello, I wonder if there's any difference between the "impedance matching" and "maximum power transfer" criterion? I assume in both cases, one impedance should be designed to be the complex conjugate of the other. Thanks.
  42. M

    Why is output impedance of op amp zero?

    Homework Statement Hi. Just like the title says, why is the output impedance of an op-amp so small? (as in physically, I understand why a low output impedance is a desirable characteristic)
  43. V

    Designing a Microstrip Impedance Matching Circuit for 50Ω-j500Ω @900MHz

    I need to make an impedance matching circuit using microstrip lines. Zin --> MATCHING CIRCUIT --> ZL The input impedance (Zin) is 50Ω. The impedance at the load is 50 - j 500Ω. Design frequency of 900MHz. The board I am required to use is the Taconic RF-35. It has a thickness of d = 1.524mm...
  44. T

    Quick question about impedance paradox

    Homework Statement Hi! We have a parallel circuit on 230V, 60Hz voltage. One of the parallel's has a 0.0768H coil, the other has a 50 Ohm resistance on it. The question is: What is the effective I in the main current? Homework Equations Z = Lw The Attempt at a Solution OK, so I...
  45. K

    Magnitude of voltage across impedance

    Homework Statement The following three impedances are connected in series across a 100-V, 20-kHz supply: (1) a 12-Ω resistor, (2) a coil of 100 μH inductance and 5-Ω resistance and (3) a 390-nF capacitor in series with a 15 Ω resistor. Sketch the circuit diagram, impedance diagram and the...
  46. L

    How to determine the output impedance of cmos gates?

    How do you determine the output impedance of cmos gates?
  47. Shackleford

    Electrical analog and impedance

    I'm a bit lost on this one. Also, what formula do I use for impedance? http://i111.photobucket.com/albums/n149/camarolt4z28/2010-09-19202315.jpg?t=1284947003 http://i111.photobucket.com/albums/n149/camarolt4z28/2010-09-19202817.jpg?t=1284947014
  48. D

    The collector is a high impedance when compared to the emitter.

    Good Morning can anyone help explain what this statement really means, when referring to a npn transistor in common mode, as an amplifier. "The collector is a high impedance when compared to the emitter" what's the pratical implication of this statement thanks David
  49. W

    Input resistance (Input impedance)

    Homework Statement A digital voltmeter is used to measure the resistance and voltage of a circuit. The resistance and voltage measured is used to calculate current flowing. What errors does the input resistance of the voltmeter introduce into the determination of current?Homework Equations I...
  50. Z

    Complex Impedance: Solve Homework Problem

    Homework Statement In a circuit consisting of a capacitor (Voltage across is 3.2V) and a 47\Omegaresistor (Voltage across is 4.65V), with a current of 0.0989A and a phase difference between the two voltages being 90', what is the complex impedance for the circuit? Unsure of how to work this...
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