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
249
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Transistor Analysis
Here is a problem I saw as an example of transistor analysis: (hFE is 50)
simulate this circuit – Schematic created using CircuitLab
The process is simple, the guy assumed that the transistor ...
0
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1answer
44 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 ...
3
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3answers
115 views
Why doesn't electricty flow to earth ground when I connect my oscilloscope ground clip to a floating circuit?
There are two concepts I keep reading about that seem to be conflicting each other. Firstly, whenever there's a potential difference between two points, and those points are connected, electric ...
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1answer
82 views
How can a resistor be given a positive and negative characteristic?
This question is not pertaining to a circuit, but to individual parts itself.
If for any reason, i want to make a resistor have a positive and negative charge on its either ends, what would be the ...
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2answers
74 views
How to classify power electronics components in 2 main groups?
I'm working on preparing a course about power electronics, and with my basic search conclusions. I thought that if it's possible or acceptable to classify the power electronics components in 2 main ...
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3answers
92 views
What happens to a computer as it is cooled towards absolute zero?
What happens to the behavior of a conventional circuit using conventional components as it is cooled towards absolute zero?
To make this question more relatable: What would happen as we cool a modern ...
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2answers
70 views
Bipolar Transistor Inverter Circuit Analysis
I have been trying to understand this question and I'm just not sure what equation to use for the collector current.
I'm not sure if I need to be using an output voltage function of time?
All I have ...
2
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5answers
154 views
How can I describe and explain SMPS on a very basic level without diving down in heavy maths / EE lingo?
I'm writing a book about repairing electronics. The audience level for the book is "very little knowledge about electronics" and it's mostly about the mindset and mindtools for finding problem sources ...
3
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3answers
191 views
Is space division multiplexing really multiplexing?
I don't know much about electronics, but happened upon the Wikipedia article for Multiplexing, which defined it as:
a method by which multiple analog or digital signals are combined into one signal ...
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4answers
85 views
No potential difference between the negative terminal of battery A and positive terminal of battery B?
I know that if you have two batteries, battery A and battery B, and connect the negative terminal of battery A to the positive terminal of battery B, there is no potential difference. If you consider ...
4
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1answer
422 views
Is there any relationship between frequency of signal and distance it travels?
I'm currently researching 5G technology. Many videos/articles on this topic claim that 5G is designed for communicating on lower distances (than 4G), because of higher (than 4G) frequency. So to build ...
0
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4answers
120 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 ...
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2answers
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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
100 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 ...
0
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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:
...
3
votes
2answers
429 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
77 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 ...
0
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1answer
138 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
1k 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
50 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
72 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
3k 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 ...
0
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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
70 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}...
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1answer
67 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 ...
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1answer
170 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
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1answer
229 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 ...
0
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1answer
44 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:
...
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6answers
762 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
59 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?
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1answer
112 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
57 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
121 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,...
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1answer
410 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
85 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
236 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
304 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
483 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
417 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?
1
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1answer
202 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
95 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.
2
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1answer
718 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 ...
0
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4answers
620 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
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3answers
859 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
137 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
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3answers
2k 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
247 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 ...
0
votes
2answers
294 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 ...
0
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2answers
57 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 ...
