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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3answers
170 views

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 ...
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7answers
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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 ...
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167 views

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 ...
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1answer
862 views

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 ...
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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), ...
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1answer
194 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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4answers
813 views

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 ...
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4answers
1k views

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 ...
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3answers
60k views

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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4answers
9k views

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
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4answers
505 views

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 ...
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4answers
2k 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. ...
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6answers
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 ...
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2answers
871 views

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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3answers
2k views

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. ...
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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 ...
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2answers
276 views

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 ...
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1answer
308 views

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 ...
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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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2answers
160 views

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 ...
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2answers
824 views

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}}\$?...
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0answers
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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 ...
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3answers
2k views

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 ...
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4answers
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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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4answers
15k views

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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1answer
854 views

Z-parameters. Is Z12*Z21 always greater or equal zero if a circuit has only resistors? [duplicate]

Possible Duplicate: Is equivalent resistance always lower if we add a resistor to a passive electronic circuit? Since my last question was probably badly formed and misunderstood this is a new ...
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2answers
237 views

LC circuit poor man theory

Ok, let's suppose we want to explain the resonant frequency of an LC circuit. By kirchoff laws is not so difficult ending to the equation: By using the Wolfram alpha engine I end up with the ...
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2answers
3k views

Which books should I read to gather practical and useful electronic design skills?

I need some guideance from the experienced users here, I need to know where to focus my studies: Ive been reading several electronic books, and they are quite different, I decided I want to re-learn ...
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2answers
339 views

Voltage divider ambiguity

considering the following circuit : ...
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3answers
4k views

AC Voltage source terminal polarity and grounding

Ill try to make it as clear as possible. This may seem like a simple question, but it is something that I havent quite figured out. It has to do with polarity on the leads of an AC source. Every book ...
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2answers
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Discharging a capacitor through a resistor and an LED in series

Suppose you have a capacitor of capacity \$C\$ and initial voltage \$U_0\$, a resistor \$R\$ and a LED with threshold voltage \$U_S\$ (\$U_0 > U_S\$) in series. Now I want to calculate duration \...
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1answer
461 views

Why does a transformer's ratio change?

I've connected various transformers to a circuit (one at a time) in reverse (power supplied to secondary) and I measured the voltages at both windings and found ratios very different from the ones ...
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5answers
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RC differentiator circuit explaination

This is the circuit of a basic RC differentiator, with the input/output voltage waveforms. First of all, I don't understand why there is decrease in the output voltage (discharging of charge from ...
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3answers
597 views

Is electronics driven by scientific papers?

Is electronics driven by scientific publication, similar to other academic fields? Two famous publications I came across, Gordon Moore's seminal paper, and Leon Chua's discussion of the memristor, did ...
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What is a mutator?

I'm reading this paper by Chua on the memristor. He claims that Using a mutator, a memristor with any prescribed phi-q curve ...
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2answers
680 views

Why is flux-linkage a fundamental circuit variable?

In his paper Memristor - The Missing Circuit Element, Chua theoritizes the memristor based on observations relating to what he calls the four fundamental circuit variables, namely, the current <...
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2answers
127 views

Amplifier theoretical analysis problem

I have this problem in a book and I've did good through the entire problem until I had to calculate current gain. I've been stuck for the past 30 minutes. The formula I get is different from the one ...
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2answers
1k views

I/Q (quadrature) carrier recovery

I was looking into I/Q demodulation, and when looking into the equations, I realized that the phase/frequency difference between the carrier and the LO in the receiver had an unwanted effect. The ...
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3answers
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Noise and what does V/√Hz actually mean?

Noise figures in (op amp) datasheets are expressed in V/√Hz, but Where does this unit come from? Why the square root? How should I pronounce it? How should I interpret it? I know lower is better, ...
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2answers
680 views

Is it possible to specify an equivalent RLC network for a loudspeaker?

Can an RLC network be defined that would behave in the same way as a theoretical loudspeaker? Since their behavior is frequency-dependent, would the values of R, L, and C also be frequency-dependent?
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How is phase angle calculated in an RLC circuit?

If I have a source with a phase angle, like this how may I count the phase angle of the voltages and currents across all the components, as well as the returning current? What is the angle between ...
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2answers
15k views

How is quasi peak calculated

As said in the headline, how is quasi-peak calculated? I was not lucky on google this time, so I will ask here. I'm just looking for the formulas behind the calculation, since I want to make some ...
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4answers
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Physical properties of transformers

In class, we were given equations for the transformer in terms of number of turns primary/secondary and coupling coefficient K, however effect of distance between coils, presence/absence of core, and ...
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2answers
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RC/RL circuits and frequency selection

We have a lab that wants us to simulate an RC and RL circuit, and then a CR and LR circuit (series). From reading it is my understanding that reversing order of components results in reversing the ...
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2answers
430 views

Computing rlc circuit in parallel

So, if a resistor, inductor and capacitor in series sum algebraically, how do they work in parallel? Is it \$\dfrac{1}{\dfrac{1}{R}+\dfrac{1}{\dfrac{1}{L}+\dfrac{1}{C}}}\$ ? Many thanks in advance ...
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1answer
342 views

How can I describe the behavior of an inductor without reference to a magnet?

In class we have been given an exercise to simulate capacitance, inductance, and resistance without reference to - well, without refernece to much of anything. The resistor is straightforward, ...
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How Does FM Get Around the Gabor Limit?

The Gabor Limit states that it's impossible to simultaneously localize a signal in both frequency and time. FM communication modulates the instantaneous frequency of the carrier in step with changes ...
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3answers
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What does E mean in this instance?

On all about circuits I keep seeing E in tables like this: In the table I and R make sense with the units. But the E doesn't. So where does it come from? I was looking at this article on ...