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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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98 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 ...
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0answers
39 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 ...
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55 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 ...
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55 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 ...
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90 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 ...
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1answer
81 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 ...
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64 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 ...
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4answers
224 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 ...
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74 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 ...
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3answers
71 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 ...
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1answer
69 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 ...
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316 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 ?
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180 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)...
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962 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 ...
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2answers
1k 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 ...
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1answer
317 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 ...
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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)? ...
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156 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 ...
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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?
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3answers
171 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 ...
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217 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 ...
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104 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?
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91 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 ...
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2answers
299 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, ...
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4answers
256 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), ...
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1answer
661 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 ...
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126 views

Find the equivalent reactance X(ω)

I need to find equvalent reastance of this circiut. After performin analysis i PSpice i found out it should be 28.91 Ohms, but it is not a correct answer. Can u tell me what am i doing wrong ? I add ...
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1answer
235 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 ...
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1answer
84 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 ...
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124 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....
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1answer
43 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 ...
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1answer
223 views

Question about per unit system

I have a set of impedance values for a motor referred to the stator given in per unit where: Vbase_s = Stator line to Line Voltage Pbase_s = Motor rated power Zbase_s = Vbase^2/Pbase Now I want to ...
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48 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 ...
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1answer
86 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?...
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4answers
1k 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, ...
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2answers
4k 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. ...
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28k 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 ...
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403 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 ...
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719 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 ...
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1answer
161 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). ...
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3answers
624 views

Does the inductance change in an LC filter based on frequency? [closed]

I sort of understand the formulas for inductive reactance. Do they apply to a LC filter? I have this, inductor at 700nH and caps at 120pF for a 20MHz cutoff emi filter: simulate this circuit –...
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2answers
103 views

Equivalent “capacitative reactance” for calculating rms current under mixed-frequency AC voltage waveform

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 ...
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2answers
790 views

High frequency rf resistors

I need non reactive resistors for use at LF thru HF (100KHz thru 30MHz) for use with radio receiving antennas as terminations. Carbon comp and carbon film work but have their shortcomings in stability ...
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4answers
1k views

How do reactive currents cause power transfer?

I read in 'The Art of Electronics': Power factor is a serious matter in large-scale electrical power distribution, because reactive currents don't result in useful power being delivered to the load,...
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2answers
133 views

Power calculation and Ohm's Law for Reactance

Hi I have the following question: V = 120V, I = 10 A, I lags V by 60degrees simulate this circuit – Schematic created using CircuitLab The load consists of a resistor and an inductor in ...
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1answer
689 views

How can a parallel capacitor improve the power factor of an inductive load?

In phasor or vector diagram, a capacitor that is parallel to the supply can improve power factor. I know this is practically true but I don't understand the mathematical equation: The total impedance ...
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1answer
42 views

AC analysis: finding L and R

EDIT: there should be arg[I2] instead of arg[I3] I've tried to replace V1, C1, R1 with Thevenin equivalent, but I've lost in my calculations. Is there any better approach?
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4answers
547 views

Excessive temperature on cheap soldering iron - will series capacitor fix it?

Soldering iron came in a $14 USD kit off eBay. Lots of neat stuff, but the iron became so hot as to badly damage a DIY Kit. After a 2nd chance w/ the same results, it was hacked, Heating element of ...
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4answers
1k views

Inductive reactance: frequency vs current. Why current goes to zero as frequency increases?

Suppose I have the circuit below with the frequency of the voltage source as a free parameter. Assuming the inductance is constant, the current flowing through the circuit shoud equal $$I(f) = \frac{...
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2answers
2k views

How many turns do I need for the primary coil of a transformer?

I need to know the number of turns that should be connected to 220 volts AC. I can measure resistance only, I don't have a device that measures inductance. If I need the primary coil to be 220V / 1A (...