# Questions tagged [reactance]

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

82 questions
Filter by
Sorted by
Tagged with
23 views

### 4 Conductor System Impedance

I have a +25kV 0v -25kV conductor system, involving 4 conductors located within a 30m^2 cross sectional plane, for which I need to calculate the individual conductor impedance's per meter and need ...
79 views

### Heating vacuum tube filament via capacitor

As I understand vacuum tubes (like triode / pentode) usually are designed to be heated with certain current through the filament. And usually it is about low-voltage and comparatively high-current. E....
53 views

### Electrical RL circuit problem

So I am given u(t)=325sin(314t+90°)V i(t)=14.14sin(314t+30°)A I have to find the impedance Z∠θ, value for the resistor and inductor, inductive reactance Urms∠θ = 325/sqrt2 ∠90° Irms∠θ = 14.14/...
32 views

### How to calculate reactance from an impedance analyzer circuit?

Background I have an impedance analyzer that uses the below circuit: Source One can measure impedance of the device under test (DUT) by using the following formulas: ...
56 views

### Foster's Reactance Theorem - Reactance Increasing with Frequency?

I'm currently reading a text on analog filters (Zverev) that discusses Foster's Reactance Theorem in relation to passive circuits and I was thrown a little by the text that says: "Physically, this ...
33 views

### Total phase inductance of three phase reactor

Consider a three phase reactor (inductor) using E-I or E-E laminations with phase winding on each limbs. Now inductance of R phase is given by: Lr=Lrr+Mry+Mrb Lrr: Self inductance of R-phase Mry: ...
66 views

### The resistance and magnetising reactance of the core

I did an experiment where I varied the test voltage and determine the values of the resistance and magnetising reactance of the core. What I noticed is that their values actually vary (not constant). ...
63 views

### Under open-circuit conditions, does a transformer behave more like a resistor, capacitor, or inductor?

I have the below schematic showing the equivalent circuit of a transformer under open-circuit conditions. Will the transformer behave like a resistor, inductor, or capacitor? And will this behaviour ...
103 views

### Crockcroft-Walton Voltage Multiplier Large Voltage Loss

I have a CW voltage multiplier that uses 30kV, 1nF capacitors and doubled 20kV, 5mA, 100ns diodes (for a total of 40kV). My ac source is a sine wave (viewed on the primary side of the transformer ...
32 views

### Finding equivalent circuit parameters for a single-phase AC transformer

Question: It is desired to find the equivalent circuit parameters for a single-phase 110V AC transformer. In the short-circuit condition, the transformer can be modelled by a series resistance and ...
102 views

### Are my calculations wrong for the capacitance?

In an earlier post i discussed about the effects of voltage derating on a capacitor. From here i measured the output with DC and AC applied to a highpass filter and found the cutoff frequency with the ...
44 views

### How to calculate the reactance of a capacitor with an input signal that is 2 sin waves of difference frequencies added together?

I am trying to calculate the reactance of a capacitor with an input signal that is not a single frequency. For example, x = sin(4t)+sin(5t), or a capacitor that is used in an audio circuit like the ...
102 views

### what does low reactance mean physically

What does "lower" reactance (higher susceptance) mean for a physical system, and when is it "good"? I see that it has less opposition to a change in voltage or current, but what does that mean? Lower ...
183 views

### Peak Current vs RMS Current when calculating Reactance

I am having a hard time getting a grip on AC circuit analysis. I have been taking my peak voltage/current and converting it to RMS current and RMS voltage so I can use ohms law and things like that to ...
95 views

### Voltage in RC circuit with unknown frequency

We were given the task of finding the voltage drop across R1 of the circuit below with the following alternatives: 5.8V 4.8V 4.0V 10.0V All given information is contained within the image, i.e. no ...
143 views

### Capacitor Reactance/Impedance Confusion

I always thought that capacitors (when used in phasor analysis) just had an impedance of $$1/jwc$$. I understand that impedance $$Z=R+jX$$where R is resistance and X is reactance. Now, in one book I ...
75 views

### Nonzero current at voltage zero-crossing when consuming reactive power

In a circuit that consumes some reactive power, the current waveform indicates current flow even when the supply voltage is at the zero crossing. This seems paradoxical since there cannot be current ...
329 views

### Does reactance increase noise?

Impedance is made of resistance and reactance which is capacitance and inductance. I read that increasing resistance increases noise, but what if capacitance or inductance is increased, does the noise ...
75 views

### Trying to analyze the audio attenuation.. Is this analysis correct?

I am learning about impedance. So sorry any stupid question here... Consider this circuit: I have an audio input, from 20 to 20 kHz. I want to know how the AC voltage over AB will behave as the ...
96 views

### For an ideal Capacitor, when is the current leading and when is the voltage leading by 90?

Say I have a purely restive load as a reference in parrallel with an ideal capacitive load. I know that the current through the capacitor is said to be leading by 90 degrees. Specifically though, what ...
104 views

### Rectangular Waveguide H-Plane Step Discontinuity - Equivalent Reactance for Change in Height

I have been reading Pozar's Microwave Engineering, and in Section 4.6, he goes through the analysis to determine the reactance of a discontinuity between two coupled waveguides. In that chapter, he ...
535 views

### What's the relationship between susceptance and reactance?

I was trying to find the relationship between these two online, but I found out two completely opposite answers, and I'm wondering which one is the right one. Is B = -1/X or is B = 1/X ?
243 views

### Why inductive reactance has two formulas

We know inductive reactance XL will have two formulas. One is XL = 2piFL and other is XL = V/I (Ohm's law). Why we have 2 formulas for inductive reactance. Is the solution ( inductive reactance value)...
2k views

### What is the difference between Instantaneous current (i) and current (I) in a purely inductive circuit?

I was reading about AC inductor circuits on All About Circuits: Link: https://www.allaboutcircuits.com/textbook/alternating-current/chpt-3/ac-inductor-circuits/ Consider this circuit of a purely ...
2k views

### Why induction motor draws more current when load is increased?

Please forgive me if I'm asking something already answered but I couldn't find specific information on this one. I am aware that a coil has inductive reactance when powered by AC besides the ...
425 views

### Does leakage reactance of transformer depend on quantum of load?

In a single phase transformer, considering copper losses and core losses, I want to find whether the leakage reactance is affected by change in load on the secondary? I was unable to find an answer ...
1k views

### Is the formula for inductive reactance the same when considering rectified AC?

Is the formula X$_L$ = 2$\pi$fL still true for rectified (but unfiltered) AC (in which case the frequency f, and therefore the reactance, would be doubled in the case of full-wave rectification)? ...
179 views

### What frequency is Ferrite Bead reactance usually given at?

I've noticed on schematics at work, when I was at uni, and on datasheets that Ferrite Beads usually (90% of the time) are only given with their designator (FB? or L?), then the reactance (XOhms) and ...
2k views

### Voltage across capacitor/inductor in RLC circuit

It is said that voltage across capacitor/inductor is higher than the applied AC voltage. How?
199 views

### capacitive reactance in a stranded wire

Can a stranded wire exhibit a capacitive reactance? I measured the real and imaginary part of a piece stranded wire using an old LRC meter( HP 4284a). Applied an open loop and a closed loop ...
283 views

### Understanding loudspeaker impedance

If I am correct, a typical loudspeaker's impedance will change depending on frequency. The impedance will be comprised of the resistance and the reactance of the voice coil. As frequency increases, so ...
167 views

### Properties of an Ideal Transformer and the reasons behind them

Why should the magnetising reactance of an ideal transformer be very large i.e. approach infinity? What practicality does this imply?
94 views

### At what frequency will the reactance of a 200mH inductor will be 5kΩ? [closed]

I'm doing practice exam questions, I have no idea what formula applies to this question. I know Xl = 2πf*L, but the question is asking for the frequency, how can I complete this when the formula for ...
359 views

### Gain factor in real Resistance and Reactance (AD5933)

I'm trying to develop a system for bioimpedance measurement with the IC AD5933. The AD5933 is a high precision impedance converter system that combines a frequency generator with a 12-bit, 1 MSPS, ...
266 views

### Is current calculation in copper wire for AC simple or not?

I'm trying to learn electronics by myself, and I'm starting with simple current calculations. Let's assume we have a straight wire of length L connecting a source and a sink. I know the voltage (V), ...
831 views

### Why inductive and capacitive reactances have opposite signs and why they cancel out eachother?

For example in a series RLC circuit with ac source why total reactance is inductive reactance minus capacitive reactances ? I dont need any mathematical proof. Can anyone provide me a a logical ...
331 views

### Complex reactance formula explanation

Can someone explain the math behind the following relationships between the equalities in a capacitor's reactance? $$X_C = \frac{1}{2\pi f C} = \frac{-j}{\omega C} = \frac{1}{j \omega C}$$ For ...
101 views

### Finding total impedance

I have a circuit as shown below simulate this circuit – Schematic created using CircuitLab Where R1, R2 are resistors. jX1 and jX3 are reactants, and jB2 is admittance. That being said, I'm ...
155 views

### How can AC current be limited with reactance?

Since resistor dissipate electrical energy by converting it to heat, while capacitors and inductors store electrical energy I believe using reactance will waste less energy. My source is 225 V, 50 Hz....
47 views

### How do I use series and parallel combinations of inductors and resistors to achieve a certain resistance+inductance?

I'm building a current driver for a load of characteristics 20mH and 5ohms. I don't have the load with me so I'm trying to create it using inductors + resistors so I can test my driver ckt. I have ...
50 views

### Induction Motor - Reactances and Leakages

In the induction motor equivalent circuit (either Thevenin or otherwise), the rotor, and stator leakages and reactances are necessary for any useful calculations. How does one estimate leakages and ...
98 views

### Calculation of the input impedance of reactance modulator

The figure 1.36 is a circuit of reactance modulator which is equivalent to a tunable inductance. I know the input impedance expression is Zin = (Z1 + Z2)/(1 + gm*Z2), but how to derive this expression?...
2k views

### What effect does Permanent Magnet have on an air-core coil?

Given an air-core coil of known inductance and a given frequency of applied voltage, you can predict the coil reactance, the current, and the voltage/current phase relationship. What effect, if any, ...
5k views

### How to Derive Capacitive- and Inductive Reactance Formula

I've been searching around the internet to find out how to derive the reactance formula for capacitors and inductors. But I couldn't really find anything, so I thought why not make a post about it. ...
37k views

### How do I find C & L from XC and XL?

Calculating Capacitance and Inductance from Capacitive Reactance and Inductive Reactance I'm trying to find the inductor (L) and capacitor (C) values using the inductive reactance (XL) and capacitive ...
431 views

### Phasor and Vector in AC circuit

Phasor is used to represent an AC quantity but for fixed frequency resistance and reactance of the circuit are not alternating but still they are represented by phasors. So is it right to call them ...
777 views

### Current through heating element lower than resistance suggests

The fuser lamp (the heating element) in my laser printer broke from one of the ends. I measured the resistance of the, almost full length, wire which was 6 ohms. I tried to fix it by connecting the ...
168 views

### Is reactance in AC circuit is also alternating?

Usually the capacitive reactance in a a circuit is represent in phasor form as X(c)= |X(c)|$\angle 90$. If we convert this phasor expression to sinusoidal expression we get. X(c)= |X(c)|sin(wt-90). ...
I want to analyze a very simple circuit subject to a not-so-simple driving AC voltage waveform. In particular, my circuit consists simply of a single capacitor with capacitance $C$ and an AC voltage ...