# 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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### 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....
1answer
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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)?
4answers
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### 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'...
1answer
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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 ...
0answers
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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 ...
3answers
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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 ...
6answers
862 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 ...
0answers
94 views

### 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 ...
2answers
3k views

### 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 ...
1answer
294 views

### 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 ...
1answer
25 views

### 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?
2answers
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### 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 ...
2answers
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1answer
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### 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 ...
2answers
4k views

### Voltage across capacitor/inductor in RLC circuit

It is said that voltage across capacitor/inductor is higher than the applied AC voltage. How?
3answers
298 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 ...
4answers
572 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 ...
3answers
296 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?
1answer
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### 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 ...
2answers
483 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, ...
4answers
311 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), ...
1answer
2k 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 ...