# Questions tagged [inductor]

An inductor is a 2 terminal passive device that stores energy in a magnetic field.

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### How can there be a current without a voltage?

Recently while trying to understand inductive AC circuits better, I got very confused with a question. Let's suppose we have a purely inductive AC circuit with ideal wires and a switch. Let's also ...
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### Energy stored and Lagging of Current In a Inductive Circuit

In a purely Inductive AC Circuit, the voltage/emf Leads the current in phase by 90. The graph between Voltage and Current is given below: Now can anyone here please tell me in a more intuitive way ...
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### Stability of input filter in SMPS - Theoretical explanation

I read the Application note Wurth Electronics ANP008c about negative resistance of a SMPS input and how to avoid oscillation when using an input LC filter. I'm asking for a theorethical clarification ...
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### How to choose a inductor for a buck regulator circuit?

I am designing a buck-regulator circuit, with possibly the MAX16974 as the regulator. I have never done such a thing before, and actually not too much analog electronics at all. I got stuck at the ...
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### Simulating a variable mutual inductance model

Can we simulate a time varying mutual inductance in Matlab Simulink (or any other simulation tool). Matlab Simulink has a variable inductor, but I could not find not mutual inductor.
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What is a ferrite bead? How is it different from an inductor? How is it rated? What are its important parameters? What allows me to chose between an inductor or ferrite bead to filter out frequencies ...
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### How to model an inductor using a behavioural voltage source in LTspice (to get time-dependent inductors)?

I am trying to make a time-dependent inductor in LTspice, but it is not as easy as for resistors which allow values directly depending on 'time'. I tried using the characteristic equation of an ...
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### Transient analysis of inductor circuit and back EMF

In a lecture exercise from a circuit course, I encountered the following circuit with only an inductor and a voltage source. The $v$ vs $t$ and $i$ vs $t$ graph is as follows: -The KVL ...
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### How do you choose an inductor for connecting separate ground planes?

On a board with separate analog and digital ground planes connected at one place, the connection is often made with an inductor. How is this inductor chosen? Obviously it has to be able to handle ...
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### What is the difference between a transformer and a coupled inductor?

Transformers and coupled inductors seem very similar. Is there a difference in construction? Or only in use? This question asks something similar, but the answers don't address my question: Coupled ...
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### Why is flyback air gap needed for energy storage?

Why do so many sources say something along the lines "since a flyback transformer stores energy, an air gap is needed"? I have seen this reasoning in textbooks and app notes. I thought air gaps ...
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### The sign in the formula for the voltage across the inductor

This question is about voltage induced in a inductance. I know the rate of change of current induces EMF in the inductor. The direction of the induced EMF will be opposite to the change that is ...
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### Do I need a Schottky diode as a flyback diode with PWM @ 30khz?

I use a regular diode (1N4007) as a flyback diode for a 250ma 5v fan. My transistor is a <...
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### Application of Complex Numbers [closed]

I was just wondering how complex numbers can be applied in electrical engineering and why we use complex numbers over regular, real numbers for this application (e.g what capabilities does the complex ...
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### "A zener with series diode"?

So I'm still reading The Art of Electronics Third Edition. On P.39, when dealing with inductive "kick", I found this sentence: For the fastest decay with a given maximum voltage, a zener with ...
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### Inductor vs a capacitor

I'm a Trainee electrician and pc hardware enthusiast. I was just wondering why a mixture of inductors and capacitors are used on motherboards? Why not just use capacitor? I thought the inductor stores ...
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### What are the behaviors of capacitors and inductors at time t=0?

Do capacitors act as an open circuits or closed circuits at time t=0? Why? What about inductors? I tried it out, and what I got was this: Initially when I opened the switch, the capacitor acted like ...
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### How does an inductor store energy?

I know that the capacitors store energy by accumulating charges at their plates, similarly people say that an inductor stores energy in its magnetic field. I cannot understand this statement. I can't ...
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### How does a transformer transmit power from the primary to the secondary?

I'm trying to get my head wrapped around transformer operation and in the process regretting the times I snoozed in my Electromagnetics class as a EE student back when I was a lad :) I'm looking for ...
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### What might be the cause of high pitch sound coming from a switching regulator circuit?

We designed a switching regulator circuit using a 1.5MHz, internal-switch, switching regulator (semtech.com/images/datasheet/sc185.pdf). Vin is 5V, Vout is 3V3. We have an input capacitor (47uf), an ...
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### Ferrite or iron powder? How do I tell what an unknown core is made of?

Most times when I need a small inductor, I try to find the necessary core in my junk box. Depending on what I'm trying to build (RF, power, ...), a ferrite core or an iron powder core might be the ...
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### Measuring ferrite core parameters

I have large amounts of inductors and transformers from power supplies or other undocumented sources. They are of course completely unmarked and I have no idea what kind of ferrite material they are ...
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### What do phase dots on an inductor mean?

I have a SEPIC supply with coupled inductors. The inductors have phase dots. What do these "phase dots" mean? Is it important to have the phase dot in the same place?
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### Why is inductance (L) proportional with turns-square (N²)?

We start from the Maxwell's Equation $$\mathbf{\nabla} \times \mathbf{B} = \mu \mathbf{J} + \overbrace{\mu \epsilon \dfrac{\partial \mathbf{E}}{\partial t}}^0.$$ We take surface integration of ...
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### Understanding the slayer exciter circuit base voltage

I am quite new to electronics and I have a bit of trouble understanding part of the slayer exciter circuit. If we take this schematic from electroboom here: I don't understand how the secondary ...
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### Smoothing a High Current PWM

I am using a MOSFET to control the average voltage to a device by varying the duty cycle to the base as shown in the diagram below. My question is what is the best circuit to use in the "filter box" ...
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### What is the largest inductance value ever attained (in Henries)?

For example, are there inductors with values in terms of kH or even MH? 1 H inductors are not all that easy to find.
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### Variable-Gap Capacitors in LTSpice

I have seen several blog posts that discuss the concept of a nonlinear capacitor (or inductor) here, here, and here. Thanks to a concerned citizen for the references. I'm still struggling with the ...
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### Current waveform in an inductor with AC source

If we connect an AC source with a pure inductor when AC source is going through 0 volts we get the following graph of the voltage and current. There are few things in the graph about which i am ...
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### About misunderstanding of Lenz law

What I understand from Faraday and Lenz laws is that(I might be wrong): a voltage appears across an inductor when the current through it changes. And the polarity of that voltage is such that it ...
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### Why do buck (step-down) switching regulators require an inductor and diode?

So, I understand, at least at a basic level, the method of operation of switching converters, both buck and boost. What puzzles me, though, is why buck converters in particular aren't simpler. Why ...
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### Are Common Mode Choke Coils needed on USB?

I was looking over the schematic for the GumStix Palo 43 and noticed they used a common mode choke coil on the data lines coming in from USB. I understand how this design can help remove noise coming ...
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### Reduction of DC motor noise

I am designing a circuit with a DC motor 12V DC Reversible Gearhead Motors - 70RPM and some other stuff including a MCU and a LASER, all driven from a single 12V source and am concerned about big HF ...
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### Why do we want gap in the core material while designing inductor?

In some cases it is necessary that core of inductor should have a gap, unlike with transformer core. I understand the reason with the voltage transformer core; there is nothing to worry about core ...
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### Why does an inductor behave as a capacitor at high frequencies?

In truth, I've only been told this anecdotally by an instructor, but can someone explain the physics at play? I have been told that if an inductor is driven at a high enough frequency, it will begin ...
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### What operation could cause the inductor or the capacitor to explode?

In really early days of electronic school, the teacher used to say something about not unplug power too quickly at an inductor or capacitor and we were used to slowly turn the voltage generator from a ...
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### Calculating the saturation current of an inductor?

How can I calculate saturation current of a Toroid inductor, with a core? What effect does the current have on the inductivity after crossing the saturation current?
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### How to visually tell the difference between axial inductors and common resistors?

Is there a simple way to tell axial inductors and resistors apart in through-hole type PCBs? I do find the color code on both very confusing. Is there an obvious difference that I am missing? As a ...
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### Adding a gap to a core for an inductor

I'm in the process of designing an inductor for a boost converter, and I'm having a hard time finding exactly what I need for this project. I have found a core size/shape that appears to work except I ...
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### Does this experiment show that Kirchhoff's Law hold when there's a changing magnetic field involved in a circuit?

In this video, the electrical engineer and youtuber Mehdi Sadaghdar (ElectroBOOM) disagrees with another video from professor Walter Lewin. Basically, professor Lewin shows in an experiment that if ...
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### Can inductor voltage and capacitor current change abruptly?

I understand that inductor current and capacitor voltage cannot change abruptly, but can inductor voltage and capacitor current change abruptly? I have a feeling the answer is no but I cannot explain ...
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### Why are the transformer windings in series with line and load in this circuit?

I came across this switching power supply circuit and I noticed the transformer is connected in a way I had never seen before. What is the benefit of connecting it like that? And why does the circuit ...
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### Understanding when to use basic Components

So I understand AVR assembly for the most part, and generally understand the overview of microcontrollers. but when it comes to specific components (besides the obvious stuff like resistors/batterys) ...
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### How do I use a transformer as an inductor?

Lp: Self inductance of the primary winding. Ls: Self inductance of the secondary winding. Lm: Mutual inductance between the primary and secondary windings. Assume that I need an iron core inductor ...
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### Is parallelling inductors a viable solution?

I am doing a space constrained board layout, in terms of surface area. So I found an inductor which is $15\mbox{ }\mu H$, $2.3\mbox{ }A_{RMS}$. I need about $3.5\mbox{ }A_{RMS}$, so I was ...
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### Diy inductor saturation current

I have a boost converter that will convert 12V and 11A to around 20V and 6A. Since I didn't find any inductors (in my local stores) capable of such currents and frequencies and the correct inductance ...
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### How do skin-effect and proximity-effect behave for flat-conductor power inductors?

Here is a Digikey search showing flat-conductor power inductors. And here is a picture of three power inductors found there: In this answer, by Rohat Kılıç, towards the end of his answer he explains ...
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### Using LC filter instead of RC filter in mains powered circuits

Above is a dimmer circuit. In some of these circuits I see a toroid inductor together with a capacitor forming a low pass LC filter which is called choke filter. My questions are: Why is RL used ...
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