# 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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### Can an induction motor be used to generate power?

Induction motors do not have magnets in them, instead the magnetic field the outer coils generate creates electricity, and subsequently magnetic field, in the inner coil. This means those motors need ...
1k views

### Why are circuit results different from theorised?

From the following circuit: I got the following results in comparison to my theorized calculations: Why were my result different to my calculations? Here is my calculations: Equipment used: ...
113 views

### Why is RMS used for P=VI (where there are no squares)?

I understand why RMS values are used for $$P = {\bar{v^2} \over R}$$ because $\bar{v^2}$ would be the "MS" so to speak, and then by square rooting we get the "RMS" ($\sqrt{\bar{v^2}}$), which ...
84 views

### 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 ...
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 ...
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### 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 ...
85 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 ...
92 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 ...
99 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 ...
85 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 ...
159 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 ...
198 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 ...
109 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 ...
431 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 ...
132 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 ...
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. ...
107 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 ...
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: ...
431 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 ...
91 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 ...
148 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 ...
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 ...
51 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 ...
73 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 ...
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 ...
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 ...
73 views

251 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 ...
45 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: ...
813 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 ...
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?
121 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 ...
62 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
437 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 ...
36 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 ...
101 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 ...
267 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 ...
316 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 "...
525 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 ...
469 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?
219 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 ...
96 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.
814 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 ...
721 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 ...
979 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 ...
186 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 ...
### 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 ...