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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110 views
How can Ohms law be used to calculate the resistor value for an LED when multiple voltage/current pairings give the same resistance?
Say I have a 9V supply, and I want to power an LED that requires 3V and 0.02A. From what I understand, I need to add a resistor that will drop 6V, and reduce the current to 0.02A, and I can calculate ...
7
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2answers
1k views
Estimate capacitor parameters
I am thinking of making a capacitor, just for fun/for studying purposes. And I thought of the following exercise.
In my local store, there exists rolls of polyethylene food film and aluminium foil. ...
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1answer
70 views
Average Power for “Infinite period of time” of a periodic signal
Last night in class we talked about the average power for any periodic function.
I'm just confused of why the one halves are in the bounds for this equation.
Since we are letting tau approach ...
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2answers
73 views
current speed/flow [closed]
Note
my questions are in form of explaining. its because I've scattered information (or assumptions) and it want to link them. that's probably why you can see me explaining to much?
Question part:
...
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votes
2answers
414 views
A question about electrons, charges and current
Let's talk about DC, a very simple circuit: a light bulb and a battery.
Some authors say that electrons move from negative to positive and current from positive from negative.
I always thought ...
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2answers
59 views
What are the initial conditions used to find the coefficients in the current equations?
Suppose a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged.
At t=0, the switch is closed and the battery (V1) feeds the circuit.
I ...
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1answer
69 views
How do I find the current equations for the RLC Series Circuit?
Let's talk about a RLC series circuit. R, L and C are in series with a battery and a switch. The switch is open. L and C are discharged.
At t=0, the switch is closed and the battery (V1) feeds the ...
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3answers
646 views
How to calculate the input and output capacitors of a common emitter amplifier using BJT?
Sorry if the question is stupid, but my head is still hard as a coconut and I am learning...
I am dealing with this circuit that I have calculated from scratch.
This circuit was designed to have
...
2
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1answer
48 views
What are the differences between Greinacher and Bridge voltage doublers?
I was reading a wiki article on Voltage doublers, and wondered - what are principal diffirences between two following schemes:
They all share same amount of components, but when and why should be one ...
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2answers
64 views
Help me understand what happens with the circuit when an AC signal is applied
Consider this circuit.
Transistor is 2N2222A. Ic is chosen to be 10 mA.
Hfe is 225 for that current.
Resistors are calculated to have Vbe = 0.7V and Vc = 4.5V.
I am trying to understand what happens ...
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3answers
2k views
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 ...
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2answers
53 views
Does a current source have a difference in potential?
I am doing a nodal analysis of this circuit.
I have found that \$ V_A = 10 V \$ and \$ V_B = -20 V \$ is it possible to have a situation like that? I mean a difference in potential between terminals ...
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2answers
66 views
How do I calculate I2 by nodal analysis only?
I am trying to do a nodal analysis of this circuit.
and I need to do this by nodal analysis only.
I need to find \$ i_1 \$, \$ i_2 \$ and \$ i_3 \$.
I have found that
\$ i_1 = \frac{V_B - V_A}{R_1}...
1
vote
1answer
66 views
How do I determine the unknowns for this equation?
Suppose a series RLC circuit in series with a 12 V battery and a switch initially opened. R = 100 Ω, L = 100mH and C = 10uF. L and C are initially discharged.
A t=0 the switch is closed.
I want to ...
0
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1answer
135 views
What is the meaning of current at infinite time for a series RLC circuit formula
I am reading this doc.
At one point, the author says the current equation form a critically damped series RLC circuit when a step function is applied is:
\$ I_L(t) = I_{\infty} + (B_1 + B_2t)e^{-\...
3
votes
1answer
185 views
Degenerate circuit concept and its theoretical and practical implications
I came across with the term "degenerate circuit" when I was studying solving linear differential equations with Laplace transform. I have learned that a system is called degenerate when the ...
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1answer
42 views
How do I calculate the unknowns of the current equation for a RLC series circuit?
Suppose I was dealing with the following voltage equation for the RLC series circuit:
\$ v(t) = Ae^{m_1t} + Be^{m_2t} + V_s \$
To know the values of A and B I would do the two initial conditions:
...
3
votes
6answers
555 views
What's the rationale behind these warnings about extension cords?
(Disclaimer: I've read the help center and I do understand that this is bordering on off-topic since it's about consumer devices. However I hope that I've managed to make enough on-topic by asking ...
0
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1answer
56 views
Trying to understand the transient current equation on a RLC circuit
I am reading this doc
I see this magic happening on the third line of equations...
How in the name of Math, does this
\$ Ae^{st} \$
appeared there?
Magic?
0
votes
1answer
88 views
MCU sinking current from a higher voltage source
In previous designs, I have used an MCU digital output to drive the lower side of a resistor ladder to the supply voltage, to prevent power consumption when the ladder is not being sampled:
Schematic ...
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1answer
50 views
Is this negative resistor model valid for any type of LC self oscillating circuit?
Is the following negative resistance model valid for any type of LC oscillator? If not, what are the exceptions?
Image Source is from here
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0answers
84 views
When deriving the instantaneous power equation for an AC power system, I get different answers depending on how I model the V & I signals. Why?
When I define \$v(t)\$ & \$i(t)\$ like this:
\$v(t)=V_m\cos(\omega t)\$
\$i(t)=I_m\cos(\omega t-b)\$
where \$V_m\$=Voltage Amplitude, \$I_m\$=Current Amplitude, \$\omega\$=rotational frequency,...
1
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1answer
344 views
Parallel RLC Resonance bandwidth
Good day ,I need help in understanding a practice problem that my professor gave us.
A parallel resonant circuit has Q = 20 and is resonant at ωO = 10,000 rad/s. If Zin = 5kΩ at ω = ωO
what is ...
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0answers
35 views
Understanding generator wear and rotor electrical measurements
I have a generator that I am attempting to fix, and I am getting readings that are out of spec on the rotor brushes. Per some instructional videos I found, I should be measuring 5V AC on the rotor ...
0
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1answer
75 views
Deriving resonance frequency of RLCC circuit
I am trying to determine the resonance frequency of an RLC resonator with added capacitor, as shown below:
simulate this circuit – Schematic created using CircuitLab
Two cases are easy to ...
2
votes
2answers
171 views
Does an LED’s free electrons ever run out?
I’m aware that LEDs are doped with impurities on each p-type and n-type material to increase the charge carriers of each semiconductor.
My curiosity now is, how does each side continue to have extra ...
1
vote
1answer
259 views
Basic Theory - finding voltage between two points
I'm a neophyte here trying to learn using "Practical Electronics for Inventors, 4th Edition" (which received almost a 5 star review with over 500 reviews on Amazon). The preface of the book states "...
2
votes
2answers
373 views
Should the error term of PID be normalized?
By "normalized", I mean +/-1 ~= the maximum error the system can reasonably be expected to experience, or divided by the setpoint.
Background: I am working on a PID controller for an SSR heater ...
2
votes
6answers
322 views
What is the voltage potential of ground during a short
During a short, is it possible for the voltage potential of the ground to change? Say for example, we short a 9V battery, how does the ground stay at 0V and not become 9V?
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1answer
158 views
Step Response of Ideal Inductor with Current Source
I'm taking an electronics course to get a physics minor (I'm an applied math major) and today, the professor shows a diagram of an ideal current source connected to an ideal inductor. Crazy stuff I ...
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2answers
94 views
resistance and current [closed]
I struggle to understand how if I increase the resistance in a circuit, it requires less current, based of ohms law.
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1answer
530 views
Intuitive and iterative approach to understanding of blinking LED circuit
I've used following schematics to build blinking LED circuit and it worked.
I tried to understand how it works qualitatively without solving differential equations. By this I mean understanding ...
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4answers
469 views
Is a hole in a conductor the same thing as a positive ion?
The flow of current in a (semi-)conductor is often described as holes and/or electrons moving between atoms. In this context:
Is an atom with a hole the same thing as a positive ion (cation), and
Is ...
1
vote
3answers
658 views
Doubling the voltage to a capacitor doubles the stored charge but does not make it charge slower. Why not?
This is a slightly theoretical question.
If you charge a capacitor from say a 3V battery you get Q charge in T seconds.
If you double the voltage to 6V you get 2Q charge also in T seconds.
My ...
1
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1answer
117 views
Output resistance with no lambda SPICE parameter
I have a simple current mirror and am trying to find the output resistance in OrCAD. Somewhere I saw: $$R_O=r_{ds}={1\over g_{ds}}$$ Using this formula and the SPICE bias file, I get a theoretical ...
3
votes
3answers
1k views
Moore vs mealy, why the output is delayed in the former?
I am not an engineer (software developer myself) but would like to understand why moore machine output is delayed.
I know that in Moore's machine, output depends only on the state, while in Mealy's ...
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5answers
242 views
Can I treat two identical capacitors with capacitance \$C\$ in parallel as one capacitor with capacitance \$2C\$?
Consider a circuit as shown with a battery,
$$ V_b $$
and two identical capacitors
$$ C_1, C_2 $$
(with C_2 being the one that's off to the side). Both have the same capacitance C. The resistor ...
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2answers
292 views
Should Kirchhoff's Law be changed to account for information removal? [closed]
If I have a simple DC circuit consisting only of an LED output, how does Kirchhoff recognize the fact that information has left the loop?
Since, in accordance with relativity(?), you can't have ...
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votes
2answers
55 views
What is the main carrier in a semiconductor with n-type material being electrons and p-type materials being holes?
Not even gonna lie this is for a crossword. it is a 15 letter word. I have searched online, in my textbooks and I cannot figure out what it is. Closest I've found is Extrinsic Semiconductor but it's ...
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2answers
628 views
Does electricity always flow in a closed loop and why does current flow to ground?
I have been taught that current flows in a closed loop back to the source. And with electrical distribution, current flows to ground because the whole grid is effectively grounded back to the source. ...
2
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0answers
45 views
What are (if there are any) the major applications/implications of relativistic electrodynamics in engineering? [closed]
I was wondering about the relativistic and covariant formulation of classical E&M and Maxwell's Equations. Does they have any major implication in engineering (not exclusively talking about ...
1
vote
4answers
328 views
Why earth ground connection does not leak current?
This seems like a question which has been asked multiple times on forums. I researched the problem but I still was unable to figure out the answer which I can at least intuitively understand. So in ...
0
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0answers
69 views
Connecting capacitor to the ground and potentials question
I am a newbie trying to enter the world of electronics and currently struggling with getting a good grasp of basic concepts of electricity. I understand that electrons which usually produce the ...
2
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2answers
731 views
How to calculate value of R2 in this circuit?
I'm reading a Floyd electronics book and working through some problems. This one has me stumped however. I already know the answer as it's given in the book (110k). However, I don't know how to ...
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1answer
276 views
What is behavior of this virtual ground circuit when sourcing/sinking current?
simulate this circuit – Schematic created using CircuitLab
This is the virtual ground circuit from a battery-powered headphone amplifier(direct link to schematic PDF). What is the behavior of ...
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2answers
91 views
Calculating Thevenin Resistance
I am having difficulty calculating the Thevenin resistance of this circuit
I know I need to replace the batteries with links but then I am confused about how to approach R1,2 & 3 in terms of ...
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1answer
115 views
Simplifying capacitor input network
For a design I am working with a capacitive feedback network. I can't show you the actual network, but I intend this to be a more general question as it should be applicable to any input network.
...
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3answers
73 views
Theory: Creating “LPS” transmitter for GPS receivers
As I understand it, GPS works by having transmitters with known locations send a timestamp, and calculating the time it took to receive it, so that you can triangulate your own position, (essentially ...
0
votes
1answer
112 views
Flow of current, isn't make potential difference?
I've learn some electronic knowledge at school and so confused by some questions.
Q1. IS it possible a flow of electricity without an electric field?
Q2. I've learn that moving of particle with ...
3
votes
2answers
402 views
BJT Voltage Divider Bias Circuit Theoretical/Ideal Model Help ..LTSPICE?
simulate this circuit – Schematic created using CircuitLab
I've been trying to study BJT Voltage Divider Bias Circuits. In particular, as they relate to their active region, amplification, and ...
