Questions tagged [theory]

Theory is a contemplative and rational type of abstract or generalizing thinking, or the results of such thinking. Depending on the context

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In adaptive signal processing, what does it mean for an arrow to go through a block?

For example, in this case the FIR digital filter has an arrow going through it. This is common in the signal processing comunity but very unintuitive from a control perspective i.e. where is the arrow ...
Fraïssé's user avatar
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AC Analysis Mindset [closed]

I'm just trying to solidify my foundational knowledge of ac analysis. So when approached with a basic circuit, lets say a RLC circuit, should my first instinct be to convert each group of components ...
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Help understanding the function of my circuit. (Bug swatter)

The important thing is the image below. I want to know how it works. Here's what I understand so far. First I'll identify the pieces: -The blue "packet" is a capacitor. Its a \$ 0.030 \mu F\$ with ...
DLV's user avatar
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Op amp has a biased output

I'm designing an op amp circuit to amplify 20mV, 18kHz square wave up to measurable levels (~2-3V). Why is the output signal: Biased at ~400mV Triangular (high output capacitance? is that a thing?) ? ...
andrey's user avatar
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Why do microcontrollers have so little RAM?

Maybe this is more of a perceptional problem, but it seems like microcontrollers have advanced by leaps and bounds in the last 20 years, in almost all regards, higher clock speed, more peripherals, ...
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Magnet that needs power to turn off? Inverse coil?

I have never heard of such thing. But it would really suit my needs. I'm inventing a device and during it's operation, it should be able to catch an iron object any time (with a permanent magnet). ...
Tomáš Zato's user avatar
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What would happen if an ideal voltage source was connected to an ideal wire?

I've seen it mentioned in discussion that an ideal wire doesn't exist (all wires have resistance), but even if it did, an ideal voltage source doesn't exist (all batteries have internal resistance); ...
BlueBomber's user avatar
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What is the difference between the substitution principle and Thevenin theorem?

The substitution principle (as seen in this book; in italian, sorry) Let A and B be any two part of an electrical network with voltage and current sources and only resistances, connected by ...
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Why don't infinitely many sinusoidals exist in an oscillator circuit?

A sinusoidal oscillator, takes the ambient thermal noise or any imbalance in the circuit as input and gives out an oscillation. This kind of oscillators are called to be linear. By the nature of a ...
hkBattousai's user avatar
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When is it theoretically possible to fit PCB circuit on x Layers (emphasis: x =1)

When is it theoretically possible to fit a given circuit on a certain number of layers? (Presumably PCB layers.) What is/are the name of the mathematics/algorithms that might determine this, or ...
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Theory question about "j" imaginary unit (AC circuit analysis)

I have just started to learn about AC network analysis and have some questions about "j" (or "i" on my calculator), the imaginary unit. My book doesn't go into a great deal about this, and jumps ...
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Why do op-amps keep amplifying?

I was reading an old copy of Horowitz and Hill's The Art of Electronics and I am trying to wrap my head around operational amplifiers in negative feedback circuits. As the book explains, as the op-...
Randall Cook's user avatar
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Would it be practical to build a chip that can do this math?

I was theorizing a new kind of 64-bit number for use in data storage, but then started wondering if it could become practical if created in hardware. (I believe it would be too slow if only software ...
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Why doesn't linear resistance scale proportionally with the square of length?

I have an in depth question about basic proportionality of resistance. Why doesn't it scale with the square of length? I ask this because what is causing the potential difference on two leads is ...
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Absolute and relative permitivitty

Principles of Electronic Materials and Devices - Hasap, pg: 585, he says: $$\epsilon_r = \frac{Q}{Q_0} = \frac{C}{C_0} = \text{relative permittivitty}$$ Then he says: It is important to remember ...
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Induced dipole moment and 'electronic polarization'

Principles of Electronic Materials and Devices - Hasap, pg: 586, he says: The induced dipole moment depends on the electric field causing it. We define a quantity called the polarizability a to ...
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Is there a maximum possible voltage?

This question got me to wondering if there is a maximum theoretical voltage. It seems to me there's a limit to how much positive or negative charge you could have--say, a container full of electrons ...
Loren Pechtel's user avatar
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Design vs reality and what to do when they differ

I've been trying to focus a bit more on Analog circuits lately and found that my design and actual results often don't match up exactly. An example is a Pierce oscillator I built a while back, the ...
s3c's user avatar
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How can the SI unit of resistivity [Ωm] be interpreted?

The way I interpret the resistance \$R\$ of a resistor, which has dimensions \$ [\frac{\mathrm{V}}{\mathrm{A}}] \$ is: how many volts must be applied across the resistor to achieve 1 ampere of current?...
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Voltage and Current along a Wire

In this question I am referring to this article. At first I was looking for a physical explanation of the fact that energy or the signal, respectively, travels much faster through a wire than the ...
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Am I doing this right? (LED's to music)

simulate this circuit – Schematic created using CircuitLab I have been charged with designing and making a circuit that makes LEDs brighten or dim to an audio source. At the time I thought I ...
Electrified Hare's user avatar
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Resistivity and resistance. Permittivity and?

We know that resistance is dependent on both the materials resistivity and the geometry of the material. For a cylindrical or rectangular material the resistance is: $$R=\rho*\frac{l}{A}$$ where l ...
uniquenamehere's user avatar
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At what resistance do I not see a voltage drop across a resistor?

If I have a circuit like this and measure the voltage drop across the resistor I get a value, regardless of what resistor I use: However, if I stick a piece of wood in there instead of the resistor I ...
Nate's user avatar
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Is it possible to have a continuous quantized signal or a discrete infinite precision signal?

When converting an analog signal to the digital domain I understand that one does two things. An analog signal is continuous and must be sampled in to discrete time segments (Discretization) The ...
secretformula's user avatar
29 votes
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Where does U for voltage come from?

I believe in Europe the letter U is commonly used for voltage in (eg.) Ohm's law \$U = I × R \$. I think I understand where the letter V came from, commonly used in North America. But what's the story ...
jippie's user avatar
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Biological 'Black Box' - how to test for underlying logic?

Firstly, I am a neuroscientist - so bear with me! I have a collection of connected brain cells (network) and a means of recording the electrical output, as well as manipulating the input to the ...
Peter's user avatar
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What are the technical challenges to store electricity from lightning strikes? [duplicate]

I ask myself that question every time I watch a Tesla documentary. So, let's get some answers down so the smart ones can think about it and we can clean-up our environment. There is free electricity ...
AlJo's user avatar
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36 votes
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When people talk about a device "drawing" current, what do they mean? Why do devices under load "draw" more current?

In my (extremely rudimentary) understanding, the amount of current flowing in a circuit is determined by a) its resistance, and b) the voltage of the power source (voltage from beginning to end), ...
Chris Cooper's user avatar
1 vote
1 answer
205 views

Radios and Power [closed]

RF newbie here. Lately I've been experimenting with RF. I built some simple oscillators, managing to get a tank circuit working as well as buffering the 1 megahertz output of a tin can oscillator. ...
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Series/Parallel DC circuit analysis training issue

I'm blocked in this exercise. I don't get how I can compute R1/R2/R3 voltage. Here's the schema : simulate this circuit – Schematic created using CircuitLab So I was able to calculate some ...
Emmanuel Istace's user avatar
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Current divider rule calculation issue

I'm doing the exercises from Wisc-Online. This one I think they are really great to learn and practice and have already done a bunch of their practical trainings. But here I'm starting to be crazy. I ...
Emmanuel Istace's user avatar
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3 answers
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What does common mode voltage stand for in an instrumentation amplifier?

I was reading a text about instrumentation amplifiers. I couldn't find any easy explanation what really common mode voltage means and its importance.
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How does a domestic appliance "know" how much current to draw?

I have a small wall plug which takes 240V 50Hz AC from the mains, and can give me 500mA 5V DC. I suspect there is a transformer stepping the voltage down and a bridge rectifier converting the AC to DC....
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How would i go about finding Rl when rl is r3

How would i go about finding Rl :/ I'm so lost iv looked for examples and all they have done is confuse me
user32785's user avatar
6 votes
4 answers
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Another question concerning transistors

I know it's been asked 1,000,000 times how/what/why transistors work and I feel like I've read every answer but I still struggle with the basics. The struggle for me is the difference between ...
G Thompson's user avatar
2 votes
4 answers
3k views

Resistors and the water analogy

The the most prevalent analogy for understanding electricity is the water hose one. I personally like this because it's very understandable but I have a question about how this works with resistors. ...
G Thompson's user avatar
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6 answers
2k views

Do electrical devices "take what they need"

One concept of electronics I have a hard time understanding is if things like motors, actuators, solenoids etc. use as much power as they need or what you give them. If a motor needs 12 volts and ...
G Thompson's user avatar
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2 answers
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Differential equation into circuit and back - good book

I have had some electronics, but we only built our circuits and then measured the input / output signals with oscilloscopes... Today I found an interesting question on physics stackexchange where ...
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How does control theory apply to my real-world processor-controlled boost converter?

I have a limited understanding of control theory. I dealt with poles and zeroes and transfer functions in school. I've implemented several microprocessor-based control schemes for DC/DC converters. ...
Stephen Collings's user avatar
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2 answers
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What if you put a capacitor betwen the plates of another capacitor?

Based on: Is there a dual of the transformer? The picture of the capacitor inside another capacitor seems viable to me. If a transformer is two inductors with a common magnetic field, its dual would ...
Stephen Collings's user avatar
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How and why is "floating input" a valid state for RF/IR encoder IC's?

RF/IF encoder/decoder IC's such as this one, will accept the address-pin in one of 3 states: Floating High Low As per this excellent answer, I believe "Floating" input can assume either High or Low ...
bdutta74's user avatar
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1 vote
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Calculate current in branch using Thévenin's theorem

E1 = 20 V E2 = 5 V R1 = 10 Ω R2 = 20 Ω R3 = 10 Ω R4 = 10 Ω R5 = 5 Ω Calculate Ix. It's obvious that the Thévenin's theorem should have been used, but the implementation is a bit confusing ...
0x6B6F77616C74's user avatar
14 votes
10 answers
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Are E and B fields in phase in electromagnetic radiation?

I recently wrote this answer, in which I said: Radio waves are electromagnetic radiation. Electromagnetic radiation contains of two components, one electrical and one magnetic. These components ...
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What idea/field in electronics is revolutionary nowadays [closed]

i realize that back then in the 30's-40's Von Neumann architecture was revolutionary, parallel at MIT, information and communication theory, and vacuum tubes were revolutionary fields, in the 70's ...
Sebastian Valencia's user avatar
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2 answers
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Basic circuit analysis - diferential equation

This is the circuit I got from an example in a book "Practical Electronics for Inventors", on page 48: How can one understand that \$0=R\frac{dI}{dt}+\frac{1}{C}I\$ implies \$I=I_0e^{\frac{-t}{RC}}\$?...
Dr Deo's user avatar
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What course of study is important for someone wanting to make analog audio equipment? [closed]

I do not have a background in electrical engineering. I do have experience building audio equipment from kits and I can build circuits from schematics diagrams. What I would like to do is to be able ...
user916775's user avatar
1 vote
4 answers
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How to light a fluorescent lamp?

There are a lot of circuits on the internet for lighting fluorescent lamps. But they don't reveal the working mechanism of the lamp itself. I'm more concerned about the theory rather than the ...
hkBattousai's user avatar
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4 votes
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Early Effect, Ebers-Moll, Common Emitter Resistance, reverse alpha/beta and saturation current

Ive been reading Sedra/Smith's Micro Electronic Circuits book, and it has a lot of info which I like, however I dont know how much of it is actually practial and useful, for instance it talks about ...
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What sort of applications does the normal distribution have in electrical engineering? [closed]

Need to know just two. Sorry for posting this here (arduino). Seems there isn't a soft-questions tag. Thank you for your help.
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How to calculate a current being drawn by a full wave rectifier diode bridge?

I've been studying power supplies and diodes, all books I've read discuss a great deal of things, but there's something I haven't found, and that is how to calculate how much current a bridge ...
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