Questions tagged [reactance]

The opposition of a circuit element to a change of electric current or voltage, as happens in capacitors and inductors.

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What is the most efficient way to detect if AC mains is live for interfacing with a microcontroller?

I want to implement an electrical mains level detector to interface with a microcontroller the simplest and most efficient way possible as this circuit would always be on. I’m trying to detect when a ...
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Transformer derivation - reactance [closed]

I'm struggling to understand a detail in the derivation of the transformer: N1/N2 = V1/V2. The start of this derivation is to state that the input voltage Vi is equal to the voltage drop on the ...
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Potential problems with disconnecting resistive load from transformer

Lets say I have a setup where an AC transformer is outputting 50 Amps at 240 volts from the secondary for some other process and I add an additional purely resistive load that pulls 100 amps at 240 ...
realm god's user avatar
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When the depth of a conductor is sufficiently large, is the reactance equal to the resistance? [closed]

Is the reactance in a conductor approximately equal to the resistance in a conductor when the depth is very large? If so, why? I'm struggling to understand the concepts behind this. I believe it has ...
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Immo coil - Resistance, Reactance and Impedance - Differences needed

Since I work in an automobile lock manufacturing company, I was measuring the DC resistance of an Immo coil using a multimeter (used in automobiles for security purposes) and found out the value was ...
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Does a permanent magnet AC motor use reactant power?

I'm learning about reactant power in school, I one thing I was told is reactant power is used to create the magnetic field and induction motor needs. Does this mean that a permanent magnet AC motor ...
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Where does the power go that would have been dissipated once an impedance matching network is in place between say a source and antenna?

If a load (say antenna) was to be physically difference in impedance to the load, so you decided to place a sort of matching network to match the impedances, where does that now unreflected power go, ...
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Line resistance >> line reactance or the other way around?

Grainger and Steven write in Power Systems Analysis that "in a well-designed and properly operated power transmission system... the line susceptances Bij are many times larger than the line ...
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What is reactive power for a circuit at its resonance frequency?

Many sources I've read state that reactive power is important because it helps maintain voltage and magnetic fields in inductors, but in a circuit at its resonance frequency, the inductive and ...
Praveen Perera's user avatar
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Algorithm for impedance calculation from known I and V sinusoids, L and C unknown

I am trying to extract the impedance from a sampled signal. Specifically, I have only noisy samples of a sinusoid, of a single period, of current and voltage at a given known frequency. I am trying to ...
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Why is the energy stored in the capacitor equal to 0J at the instant the inductor is storing its peak energy when they're in a series combination?

Question is the title. An extra point would be, what would be different if now the capacitor and inductor were placed in parallel. Would it still be 0?
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Can series capacitors reduce guitar cable capacitance without signal loss?

Recently, I was reading about a so-called zero capacitance guitar cable pitched to eliminate resonant frequency shifts when using higher impedance passive guitar pickups. The company claims their ...
doktar rico's user avatar
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Electron flow in LC circuit in resonance - why capacitive reactance reduces inductive reactance to zero (by intuition)

I understand why capacitive reactance reduces inductive reactance mathematically, having a result of zero at resonant frequency. But how to physically explain the flow of electrons in series LC ...
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How do I derive capacitive reactance formula from Cdv/dt?

I know that capacitors block DC and low-frequency AC, and their reactance decreases as the frequency of the AC circuit increases. As such they are useful as high-pass filters and so forth. I had ...
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Given S-Parameters (or Y,Z,T,ABCD), how can you calculate \$Q_C\$ and \$Q_L\$ (or, how do you calculate ESR)?

Background I'm writing a .s2p/Touchstone library for Perl and I'm trying to get the Q value of a component given an S-parameter matrix. The Goal In this case I'm trying to get Q for a 10nF muRata ...
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Switching an active inductor controller with a high-side MOSFET [closed]

I need help switching an active inductor controller using inductive reactance to control the current of two feeds. The circuit I have built uses make-before-break switching just like a rotating brush ...
Marathonman's user avatar
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Can admittance (Y) be used to calculate reactance when L and C values are calculated from the Y12 and Y11 parameters like normal as X=XL-XC?

My original question sought to understand the relationship between S-parameters and reactance. In the process of trying to figure that out, this second question arose. The actual question is at the ...
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How are S-Parameters and Reactance related, can one be calculated from the other?

I know that, for example, \$X_L=2\pi f L\$ will calculate reactance of an ideal inductor, but can this be calculated for a real component model? Given the S-Parameter values at some frequency from an ...
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Should I include the resistance of capacitors and inductors (reactance) in my schematic?

I generated a DC/DC PS circuit from Maxim Integrated, and got this output: You'll notice that both the inductors and the capacitors have their respective resistances marked (in milliohms). Are these ...
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Why does this method of measuring inductance work? [closed]

I recently watched this video from EEVblog showing a method of measuring inductance. I'm probably missing something obvious, but why does this work? Mathematical proof would be great. Thanks. https://...
solenoids are cool's user avatar
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How to measure the output of a ceiling fan controller?

Background: I have an older home automation system that I'd like to use for controlling my gas fireplace (flame and fan separately). Due to the automation system's age (and unknown manufacturing ...
Arsinio's user avatar
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Determining the impedance of an unknown component

If I have an antenna and I wish to measure its impedance. I have two impedance values, Z=125.52-j207.36Ohms and Z=8.14-j39.6Ohms, and I do not know which one is correct/ which one applies to this ...
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Variable capacitive dropper power supply by means of capacitor switching with TRIAC?

Is it possible to increase the reactance and thus the current of a capacitive power supply by switching an additional capacitor in parallel using a TRIAC (e.g. zero-crossing SSR)? simulate this ...
handle's user avatar
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Will DC with a frequency have reactance?

I am getting mixed answers for the question. Quora says: There is no reactance! Xc = 1/(2 x pi x f x C), and since f=0, Xc = 0. The frequency is non-zero (for second and third picture,) though. Then ...
ExtroMechanic's user avatar
11 votes
6 answers
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What is the difference between impedance and reactance?

I mean how are they physically different? What does it mean to have imaginary numbers in the reactance?
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About power dissipation of capacitors and inductors & I-V phase difference

For instance, The Art of Electronics (by Horowitz & Hill) states that ideal capacitors cannot dissipate power, even though current can flow through them, because the voltage and current are 90° ...
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How to relate resistance/reactance to parallel/series equivalent circuits?

Problem 7A of The Electronics of Radio asks the reader to find the relationships between resistance and reactance values in any arbitrary series/parallel circuit and their counterparts in a parallel/...
Architect's user avatar
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What is the capacitive reactance in this case?

Capacitive reactance in ohms is defined as: $$X_C(\omega) = \frac{1}{2\pi f C}$$ where the unit of C is farad. Focusing on the frequency \$f\$ in the equation: If the input signal to the capacitor is ...
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How can you do "impedance matching" on USB or other serial communication lines?

I was told that that impedance matching is important when going to high speeds on USB. I assume that the "impedance" matching in practice means "reactance" matching. But, how can ...
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Why reactance is imaginary? [duplicate]

In AC circuit, cartesian impedance formula is Z = R + jX (Z = impedance, R = resistance, X = reactance). Why is reactance imaginary (for capacitors and inductors)? I cannot find a good explanation ...
Alex Chalyy's user avatar
3 votes
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479 views

Proof of capacitive reactance equation

I have a doubt about the ratio of potential difference and current of capacitor $$X_c = \frac{v}{i} = \frac{1}{\omega C}$$ If I have a sinusoidal potential difference $$v = V_Msin(\omega t)$$ and the ...
Simone's user avatar
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Why is an infinite reactance an open circuit?

I'm writing up a summary about classic impedances (resistors \$Z_R=R\$, capacitors \$Z_C=1/j\omega C\$ and inductors \$Z_L = j\omega L\$) for students starting out with AC networks. I was about to ...
Mew's user avatar
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Are impedance calculations only specific to sinusoidal inputs?

All impedance formulae we've derived in my course and calculations e.g. combined impedances in series have all assumed sinusoidal steady state. My question is, does the notion of "impedance" ...
Gary Allen's user avatar
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292 views

Building intuition on the behavior of inductors and capacitors with both voltage and current

I understand that an inductor cannot change current instantaneously, however I am not sure how that relates to the voltage. In a high pass RL circuit, for example, I know that the inductor presents a ...
Shubhankar Sharma's user avatar
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2 answers
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Current limiting rectifier with capacitive reactance (isolated)

[UPDATE] I have answered my own question with links to experimental data and theory. Please expand on that answer if you can for the reference of future readers. Thanks for replies so far and ongoing....
SavingEnergy's user avatar
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Reactance to varying DC

Input signal (a) is AC. Input signal (b) is varying DC. As (b) has a frequency but does not change direction, does the capacitor's reactance have a different effect than input signal (a)?
PaddyMak's user avatar
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382 views

Keeping a cheap, DIY transformer safe

I want to design a cheap but safe, low-wattage, always-on heater to keep a small space above freezing. (A small underground tunnel that the water pipe for an automatic horse waterer goes through.) I'...
SvdSinner's user avatar
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Effect of a capacitive or inductive divider on noise

I am used to thinking about the effect of an attenuator on a system's noise in the following way: there is some system noise (and signal) at the attenuator's input, coming from the preceding part of ...
janizer's user avatar
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What unit is expressing the effect of this capacitor in a common emitter amplifier?

I'm working through this handout I3.PDF in my attempt to understand negative feedback in amplifiers. The following formula appears, in which the author is substituting \$v_{out}\$ and \$v_{in}\$ to ...
nuggethead's user avatar
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Why does impedance decrease in an MLCC as frequency increases?

I understand that the impedance of any capacitor decreases as frequency reaches the resonance frequency, following the formula Xc = 1 / ( 2 pi f C ), but why does the impedance of an MLCC such a ...
icantalktosneks's user avatar
3 votes
6 answers
2k views

Why does wire not have large capacitive reactance?

For capacitive reactance, I am presented this formula: $$X_C = -\frac{1}{2\pi fC} $$ Where clearly, the capacitive reactance is inversely proportional to the capacitance. This confuses me. We usually ...
LeonTheProfessional's user avatar
2 votes
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How do you calculate phase shift induced by a shunt capacitor?

Given a simple loaded-line shunt-capacitor phase shifter, how can I calculate the phase shift and insertion loss at S21 caused by the shunt capacitor (varicap in my case, but for any cap) assuming I ...
KJ7LNW's user avatar
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10 votes
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What is Negative Inductance?

I am experimenting with a stripline square spiral inductor in Sonnet and the graph is showing both a positive and negative inductance. What does it mean to have a negative inductance? Why does it ...
KJ7LNW's user avatar
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1 vote
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Capacitive reactance related to frequency

Why does capacitive reactance decrease with the increase of the frequency of the applied signal? It is easy to prove why capacitive reactance decreases with increased capacitance. The more we increase ...
McCarter's user avatar
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In a RCL circuit; where V_C > V_L is the phasor angle leading or lagging?

Is this example correct in stating that the phasor angle is leading by 38.323deg?
Brandon Pillay 's user avatar
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2 answers
63 views

Why can't i calculate the Inductive reactance in this way?

Question: \$V_1=40sin(1000t)\$,what is the value of Inductive reactance? Solution : \$Z=\frac{V_1}{I}=\frac{40}{8}=5\$,so \$5=\sqrt{R^2+X^2_L}=\sqrt{4^2+X^2_L}\$,so \$X_L=3\$ But i want to ask ...
shineele's user avatar
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What is the reactance when the frequency is 80 kHz?

I recently had a test with the following question: What is the reactance of a 6.8µF capacitor at 80 kHz I found the reactance to be: \$X_c=\frac{1}{j \cdot 2\pi \cdot f\cdot C}=\frac{1}{j \cdot 2\...
Carl's user avatar
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Thevenin resistance in a fault current

In the reactance diagram, why is j0.20 (as circled in the picture) in series with j0.20 + j0.10 + j0.17. Why isn't j0.20 (circled) in parallel with j0.20 + j0.10 + j0.17 and j0.20 + j0.1333 + j0.24.
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Series Resistance-Capacitance Circuit

I have an optocoupler and I connect it to 230V, the datasheet tell me the optocoupler has a forward voltage: IF = ± 5 mA VF - 1.5 V, so, for limiting the current I need an resistor of 4.7K - 11wats, ...
Vesa95's user avatar
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Current when switching on with inductance. Role of Reactance?

When switching on the current through a coil it can be described as: \$ I(t) = \frac{U}{R} \cdot (1 - e^{(-x\cdot R/L)}) \$ For a sinusiodal current the complex resistance for a circuit with ...
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