Questions tagged [circuit-theory]
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127 questions
44
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8
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Am I insane to question that only with a closed path can electrons move?
First of all let me just state that I do not feel confident enough to tell anyone anything about how electric circuits work or anything about the physics behind them because I simply do not know or ...
- 561
16
votes
7
answers
8k
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What's wrong with parallel conductors?
Regarding AC systems (like for homes and such), a circular path is called a parallel conductor. It's illegal (according to the NEC section 310) except under certain circumstances. But I have noticed ...
- 263
16
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3
answers
8k
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Can a thyristor be built from two transistors?
Supposedly, an SCR/thyristor is just a simple, four layer PNPN semiconductor.
If that's the case..
When a circuit calls for a SCR/thyristor, and there isn't one available, can it be substituted by (...
- 1,089
8
votes
4
answers
3k
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Does a resistor between two pairs of series resistors affect the equivalent resistance?
For the below DC circuit, does the 1Ω resistor in the middle have an effect on the equivalent resistance?
If it does, how would you calculate the equivalent resistance? The rules for series and ...
- 191
8
votes
1
answer
11k
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Meaning of Sigma in Laplace transform
I found the question below in a forum and I also have same problem. Unfortunately, there is no answer at all so I will post it here hope someone could make it clear.
A gain relation in a circuit of ...
- 1,661
7
votes
3
answers
3k
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How do I really calculate these resistors?
I am learning about it.
I would like to focus on this circuit
I am trying to calculate R10 and R11.
I want Ic = 10 mA. Transistor is 2N2222A.
This is an amplifier. If I understood how amplifiers ...
- 847
6
votes
1
answer
1k
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What is the maximum current of an electronic load?
Here is the specification of an electronic load:
If the load is set in current mode, the current is limited to 25 A.
Nevertheless, if the current is set in resistor mode, I could think that it is ...
- 2,610
6
votes
3
answers
624
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Is reactive power periodic in nature? What is the exact difference between active power, average power, and real power?
Consider an RC circuit which is supplied by a sine source
$$v(t)=V_m\cdot \sin(\omega t)$$
The current through the circuit will be
$$i(t)=I_m\cdot \sin(\omega t+\phi) \\
\phi=\arctan \left(\dfrac{1}{\...
4
votes
7
answers
1k
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LEDs seem to automatically self-regulate to achieve ideal voltage across terminals
Note: the key question is now in bold at the bottom, for the people who have had trouble figuring out what I'm trying to ask. Sorry about the meandering explanation.
I've been experimenting with ...
- 133
4
votes
2
answers
5k
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Is voltage and current sources linear or nonlinear?
From the circuit theory it is known that an element whose response is linear is called linear element such as resistor, capacitor. For example, in case of resistor the slope between V and I is a ...
- 163
4
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1
answer
156
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Linear Circuit and System Interpetation
My question is about interpreting a given circuit as being itself a linear system. We know that a linear system needs to satisfy the superposition principle: if \$f(ax_1+bx_2)=af(x_1)+bf(x_2)\$. This ...
- 705
3
votes
1
answer
224
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Clarifying an article on switch debouncing - something about leakage current causing trouble
I recently read this article on switch debouncing: A Guide to Debouncing - Part 2, or, How to Debounce a Contact in Two Easy Pages, by Jack Ganssle.
The article is on choosing the correct resistor and ...
- 45
3
votes
3
answers
2k
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How to find the value of alpha in this curcuit?
I have tried to solve this way but i am not sure how to proceed from here:
[![tried solution][2]][2]
- 171
3
votes
1
answer
647
views
Why is this two-inductor circuit first order?
I have the following circuit with two inductors. Apparently this is a first order circuit (judging from my solutions for \$ i_1, i_2\$; and circuit simulations) but it's not intuitively clear to me ...
- 705
3
votes
1
answer
175
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Resistive network with two voltage sources
Update: (I updated the description/Question for clarity)
I am currently stuck trying to solve a seemingly simple resistive network. The voltages U1 and U2, aswell as Rr are known. The unknown ...
2
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2
answers
3k
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Do higher voltages cause heating?
I'm trying to wrap my head around energy consumption in general.
For some background info, I'm an engineering student and am familiar with the usual electrical engineering formulae
Here is what caused ...
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2
votes
2
answers
121
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Why losslessness requires voltage and current must be both zero?
In the textbook (pg. 260 Linear Circuit Analysis, by Artice Davis), losslessness is defined in such way:
Losslessness: If w(\$\infty\$) = 0 for any v(t) and i(t) waveforms supported by the
element ...
- 1,448
2
votes
4
answers
288
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Relation between transmission line and circuit impedance
What is the relation between the impedance of lumped components and the characteristic impedance of transmission lines?
I have noticed that in some cases transmission lines are loaded with lumped ...
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2
votes
1
answer
204
views
How do you prove that a certain circuit is impossible to construct with a certain amount of switches?
I wanted to make a subcircuit, which, if viewed as a black-box, is a two-terminal device, which can behave as
a closed circuit (0 Ω)
25 Ω
50 Ω
an open circuit (∞ Ω)
(sans non-idealities of course; i....
- 5,497
2
votes
3
answers
924
views
Is it possible to constrain a circuit's voltage supply to a specific voltage range?
I have a circuit which requires exactly 12v to work properly, with a maximum tolerance of ±0.5V. The circuit is arbitrary and one can think of it as a theoretical question, but let's say that it ...
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2
votes
1
answer
185
views
How to analytically find node voltages in a voltage doubler?
Given a voltage doubler circuit:
simulate this circuit – Schematic created using CircuitLab
You can figure out what should happen in stead state if \$R_L=\infty\$ and \$R_s=0\$. In that case, \$...
- 2,116
2
votes
1
answer
283
views
Isolated circuits: can their reference voltages (GNDs) be at the same potential?
Suppose there are two independent circuits isolated from each other. If they are isolated, the impedance is very high between them (ideally infinite) and there is no current flowing from one to the ...
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2
answers
9k
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First order circuit with t=0+ , t=0-?
Yesterday I tried to solve a question in a second order circuit , but I couldn't ! because I have problem understanding the concept of 0+ , 0- !
So let me try it in a first order circuit , it ...
- 41
2
votes
2
answers
122
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Good way to obtain voltages along (non-uniform) \$RC\$ line
I have a long RC line, e.g.:
simulate this circuit – Schematic created using CircuitLab
Is there a good way to obtain the voltages on nodes V1, ..., Vn (possibly approximated) at a specific ...
- 1,332
2
votes
2
answers
237
views
Transient solution of current in circuit with two coupled inductors, with resistances
Circuit in question is given below. I want to find why I can not get the
same current waveform as PSpice gives me.
Basically I want to calculate formula for i1(t) by hand and get something as close ...
- 41
2
votes
1
answer
93
views
Maximum error of nominal resistor combinations
Suppose you have resistors which have nominal values of \$R_0\$ or \$2R_0\$ but can vary to be anywhere between \$(1 ± .03)R_0\$ or \$(2 ± .06)R_0\$, respectively, so each can have about 3% error.
...
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2
votes
1
answer
2k
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Why the opposite of the passive sign convention is not the active sign convention?
Studying the fundamentals of circuit theory, I was reading the Wikipedia article on the Passive Sign Convention and found out about the Active Sign Convention (ASC). After searching many introductory ...
- 439
2
votes
1
answer
614
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Finding some variables in a second-order circuit?
Can any one please help me solving these questions .. I always get a wrong answers :/
The first order circuit is much easier than this one !!
This is my answer :
for the first time i thought it ...
- 41
2
votes
2
answers
104
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Complex Power Conservation or "Boucherot's Theorem" - a proof without Nodal Analysis
Brief Question
I'm trying to figure out a proof for the Complex Power Conservation Theorem, which does not use Nodal Analysis.
Theory I know
In my university this theorem has ben taught with the name &...
- 21
2
votes
0
answers
147
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Why is any general cutset equation a linear combination of fundamental cutsets?
I have currently started studying circuit theory and my professor introduced graphs to form kvl and kcl equations. When we form the cutset matrix using fundamental cutsets it is easy to understand ...
- 121
2
votes
1
answer
160
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What hypothesis are needed to support the following argument on a three phase system?
Given the following three-phase system:
simulate this circuit – Schematic created using CircuitLab
Suppose to set 2 wattmeters as follows:
\$P_{21}\$ which measures current \$I_2\$ and ...
- 1,090
2
votes
2
answers
1k
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What happens to Filtered High Frequency Noise?
How to filter out high frequency noise from power supplies has been covered ad nauseum, but no one ever discusses what actually happens to the noise itself. Surely it doesn't just disappear? My ...
- 23
1
vote
2
answers
267
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How to write the equation for the input side of a JFET?
I have been reading about the voltage gain of JFET, but I am unable to understand how to write the equation for the input side. Can somebody explain the method to write the equation for the input ...
- 147
1
vote
6
answers
3k
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Time delayed deactivation of a circuit
In a simple electronic circuit with a momentary switched LED (or bulb, tube etc.); what can be done to trigger the LED for several seconds before proceeding to break the circuit?
In other words; I ...
- 1,089
1
vote
4
answers
767
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Synthesizing an impedance given by transfer function (poles/zeros) using a passive network
I would like to synthesize an arbitrary passive network based on a given transfer function (poles/zeros).
The origin is the output impedance of a voltage regulator for which I want to find an ...
- 1,332
1
vote
2
answers
131
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Transient circuit analysis with additional source
The circuit in the image below is what I get when I open the switch of a larger circuit which I have already analysed. Therefore, I know the initial condition.
simulate this circuit – Schematic ...
- 147
1
vote
3
answers
132
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What is the current - voltage relation in a wire?
This is a question from a TV game show. Fill the blank with appropriate words.
Current flowing through a wire is ... to the voltage drop across the
wire.
The answer in the dots is "proportional"....
- 1,661
1
vote
4
answers
159
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Energy Transport in Circuits
I've been reading about how energy is actually transported in circuits (I first read about it here: http://amasci.com/miscon/ener1.html). The description in this article of why electrons don't move ...
- 705
1
vote
1
answer
291
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How to simplify this complex DC circuit?
I find it very hard to simplify this circuit. Currently practicing for my removal exam and this was one of the problems I failed on one of my previous exams.
Especially the middle part makes me so ...
1
vote
2
answers
2k
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dependent current source polarity
In this question, I apply the current cycle law,
I find the current i1 to 25uA. I find the voltage on the dependent current source -2 volts. When I go through the formulas, there is no problem here.
...
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1
vote
3
answers
1k
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How to find current in this circuit passing through 4ohm resistor
Below I have added my solution after the question so please let me know how I can solve it after the last step:
These steps to follow to solve the question from where i left in my post ,
FYI :As ...
- 171
1
vote
1
answer
90
views
Does KVL guarantee identical voltages/currents in similar circuits?
I have a question that is a bit abstract. Assuming I have two proper linear circuits, A and B, which have:
The same ideal components (for example, voltage source, inductor, capacitor, resistor)
The ...
- 270
1
vote
1
answer
104
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Transient Charge Density in Conductor
Veritasium's (Derek Muller's) video How Electricity Actually Works makes the claim at
4:44 that:
The truth is, if you average over a few atoms, you find the charge density everywhere inside a ...
- 27.8k
1
vote
1
answer
153
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capacitive proximity sensor - how does it work
I know 3d printers such as the i3 use a Capacitive proximity sensor to try compensate for the uneven surface of the print bed. for example this one seems to be popular
https://www.amazon.co.uk/gp/...
- 3,373
1
vote
1
answer
129
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Disambiguation of AC Analysis and Small Signal Analysis
I am trying to understand Small Signal Analysis (SSA) for Diodes and BJT transistors through different textbooks but I have some issues.
Is AC Analysis the same as SSA? I have seen hints that imply ...
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1
vote
1
answer
358
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Meaning of the determinant of an ABCD transmission matrix
In a thesis, [1] I found the following statement:
To determine [characteristic impedance and] dispersion relationships for
an arbitrary reciprocal network having the transmission matrix
$$ \begin{...
- 1,332
1
vote
1
answer
612
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How to deal with a negative resistor in Z parameters of a passive network?
This question is so basic but for some reason I am not seeing it: Assume an arbitrary passive 2-port network having only isotropic materials. This implies S21=S21 and Z12=Z21 (see https://www....
- 1,332
1
vote
1
answer
221
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Complex impedances of capacitors/inductors in the phasor domain
I'm trying to verify the complex impedances of passive components in the phasor domain (not s-domain). Take for example the inductor, whose element law is \$ v = L \frac{di}{dt} \$. Assuming a complex ...
- 705
1
vote
1
answer
588
views
Norton Equivalent and current convention
Consider that we are trying to find the Norton equivalent of a certain circuit . According to my understanding , while finding the short circuit current or the Norton current , we should point it ...
- 37
1
vote
1
answer
73
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Finding the unknowns of a current equation leads to non-sense
Suppose a series RLC circuit that is critically damped.
Circuit is RLC in series with a DC voltage source \$ V_S \$ and a switch initially open. Capacitor and inductor are both discharged.
at t=0 ...
- 847