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Questions tagged [electric-circuits]

An electronic system, with closed loop current flow, and relative electrical potentials present across electrical components.

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+50

Free Electron-Bond Electron Interactions

I am reading an introductory textbook on electronics: Practical Electronics for Inventors by Paul Scherz and Simon Monk. In a section discussing the motion of electrons in circuits, the textbook ...
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125 views

Can the Hall effect drive a current?

In the Hall Effect current is passed through a wide strip of metal in a perpendicular magnetic field. Since (some of) the negative charges in the metal move but the positive ones stay put, the ...
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Is high frequency alternating current capable of rotating induction motor?

I have 100khz AC power that can light up a bulb, can I use this to run small induction motor? I want the Lorentz force to push rotor coil, I know that motor would not rotate at 100000hz rate but it ...
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Why are(n’t) rechargeable batteries damaged by partial charging?

Originally asked in ElectricalEngineering.SE, but I was told Physics.SE might be a better place to ask. Over the years, I've come across websites and people with different opinions on the "correct" ...
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Photovoltaic Device and Photon Absorption

When dealing with a photodiode photons with lower energy (such as red light) penetrate deeper then a photon with higher energy (such as blue light). The responsivity of the photodiode has a lower ...
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71 views

In series RLC circuit, does decreasing the capacitance value really make the circuit more capacitive circuit?

This seems very counter intuitive to me. How can decreasing the capacitance value make the circuit more capacitive ? The math tells me so : If $C$ decreases then $X_c = \dfrac{1}{\omega C}$ ...
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193 views

What is Capacitance for a Spherical Shell pair?

Consider three Scenarios : 1) In this case , we are Calculating $$\frac{d(Q_b)}{d( \triangle Vab)} $$ 2) In this case , we are Calculating $$\frac{d(Q_a)}{d( \triangle Vab)}$$ 3) In this ...
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267 views

Approximating the equivalent resistance of a large resistor network

Per the elegant solution of this Phys.SE question we can find the equivalent resistance between nodes $k$ and $l$ of a resistor network like this: $$R_{kl} = {{\rm det}A^{(kl)} \over {\rm det} A^{(l)}...
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What if in potentiometer, the loops are not balanced to cancel the potential and current flows?

As described in the book (image) that loops should be balanced with equal potential with help of the galvanometer. What if the we do not balance it to zero and have some current flowing? Can we still ...
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What is the most critical aspect of a CDU's output in order to obtain load discharge?

I am trying to better understand the exact circuitry and physics that go into a functioning CDU. Currently, I understand that CDU’s, also known as Electronic Detonator Units (EDU’s) consist of ...
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86 views

Electrical circuit analogue of a nonlinear pendulum

Is it possible to make an electrical circuit analogue of a nonlinear pendulum? To model the equation $$y'' = -\sin(y)$$ They did this on analog computers in the past, but how? How to model the ...
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Why is the current measured through a thin film increasing with time? (experimental question)

I'm doing an experiment: I'm thermally evaporating a metal in a vacuum onto a quartz (very insulating) substrate, between two gold contacts that I use to measure the current through the (growing) film....
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Concepts in Gabriel Kron's later papers

Gabriel Kron was an important research electrical engineer known for applying differential geometry and algebraic topology to the study of electrical system. Towards the end of his career he published ...
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261 views

The origin of contact noise?

I was trying to measure the noise of a device with metal probes. I was not sure whether I should trust the results because I was told contact noise might contribute to some degree. I am a little ...
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27 views

RMS values and phasor diagrams

In RL circuits (AC source) we use vectors to calculate the total voltage, I understand that we cannot add them algebraically because they do not exist at the same time as we are using rms values for ...
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Human vs. machine energy expenditures

I've read that a typical human-powered bicycle power generator generates around 100W. For the same amount of effort, the bike travels probably around 20k/h on a road. Does that mean it requires 100Wh ...
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Why is the maximum voltage applied to the coil different when disconnected from the battery?

In this RL circuit, the time to reach the point V=0 (after the switch was turned to (a)) was about the same as the time after switched to (b). But my teacher says, (in the experiment) peak voltage ...
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Could the tether of a space elevator be used as a single-wire transmission line?

If you're unfamiliar with single-wire transmission lines: https://en.wikipedia.org/wiki/Single-wire_transmission_line It seems that a material with high conductivity (eg: certain configurations of ...
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23 views

How to calculate the total emf and current in a secondary winding composed of multiple materials

In transformers, flux swings in the primary winding induce an emf in the secondary. Typically the secondary is taken to be a single material, but if it is instead taken to consist of multiple ...
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28 views

Toroidal shaped Tesla Coil

Since toroidal shaped transformers perform better than conventional E core transformers. Would a Tesla Coil that is shaped in a toroidal shape perform better than Tesla coils that is shaped ...
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61 views

What is steady state current?

I am currently trying to understand the following paper: On the nonlinear electromagnetic coupling between a coil and an oscillating magnet http://iopscience....
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Designing capacitor or resistor systems where capacitor or resistor can bear limited voltage

A capacitance of $2\ \mu F$ is required in an electrical circuit across a potential difference of $1.0\ kV$. A large number of $1\ \mu F$ capacitors are available which can withstand a potential ...
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60 views

Current obtained using half wave rectifier

In a transformer the voltage in the secondary coil is 180 degrees out of phase with the voltage in primary coil. So the current should also be out of phase. However in all the graphs I have come ...
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Can a static magnetic field passes through an electric charged surface?

I have two questions the first (look at Fig1) : I have a static magnetic field perpendicular to a charge surface, where the charges are moving in (let's say) the y-direction and the magnetic field in ...
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105 views

LC circuit problem

I am currently working on a LC circuit problem where there were given this question that I couldn't understand which is : theoretically justify the shape of the curve (the spring curve) by ...
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184 views

Infinite square grid of two different resistors

We have always heard about infinite square grid of identical resistors, in which the equivalent resistance is easly derived by simmetry consideration. However, how would we compute (or at least upper ...
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268 views

How is a Potential Difference Created in Photo Voltaic Cells?

In order for photo cells to produce current, N and P type material are joined to create a depletion zone. I understand how incoming photons can dislodge electrons from their atoms in the N type ...
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176 views

Multiple infinite ladders of resistances

I'm a bit stuck with this problem. I'll post the exact statement below: Consider the circuit given. Calculate the voltage across the 100Ω Resistor. The configuration of $I^{th}$ sub-circuit is given ...
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Is this Thevinin equivalent of a voltage divider, correct?

Found the PDF version of The Art of Electronics (Horowitz and Hill) recently, and, having nothing better to do... I thought I'd give it a read. It wasn't long before I hit a wall (courtesy: my inept ...
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540 views

A simple potentiometer problem

The question is given in the pic attached. Why should there be a change in the balancing length when the keys are closed for resistances $R$ and $X$ one by one? Shouldn't the potential between $A$ ...
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47 views

Maximize resistance in a 3 ring symmetrical circuit

I came up with this question as I tried to extend the problem of maximizing the resistance in a circle by selecting two points where to connect the electrodes. The solution for this problem is obvious ...
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60 views

Ohm's law and resistor networks

Consider N electrodes embedded in a nonuniform resistive material. We have a map from the voltages of the electrodes V_i, to the currents through electrodes I_i. What properties must this map satisfy? ...
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115 views

External quality factor $Q_e$ of RLC circuit capacitively coupled to feedline

I am interested in series RLC circuits coupled to transmission lines. Coupling can be done either inductively or capacitively. The external quality factor $Q_e$ is defined by coupling. I have found ...
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What happens when a metal piece is inserted into a live inductor connected in series with a resistance and DC voltage?

Suppose after the metal piece is inserted, effective inductance becomes n times the initial value. It is meant to have been pushed in abruptly, what is the current through the circuit just after the ...
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343 views

Sensitivity of Wheatstone bridge

I was going through my textbook and it told me that the sensitivity of a metre bridge is maximum when the resistances in its arms are equal (at balanced conditions) and for a potentiometer if the ...
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78 views

Is this equation for current in a superconductor correct?

Assuming we have kept a constant source of voltage, is the current gained through an ideal conductor given by $I=\frac{2Vq^2t}{m}$ where $q$ is the charge per volume of the carrier and $m$ is the mass ...
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frequency passage inside AC ciruit

I've been checking YouTube about AC circuit lesson and been hearing about inductor passing low frequency and capacitor passing high frequency from alternating current and what does that mean by ...
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Minus sign in analyzing RC with changing emf circuit?

I'm learning electromagnetism from Purcell's book. He say that if we have the following circuit: $$-\frac QC + RI = \mathcal E_0\cos\omega t~,\quad I = -\frac{\mathrm dQ}{\mathrm dt} $$ The ...
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55 views

Determine potential function given initial conditions?

Assuming a radially symmetric circular disk (let's say r=1). Given two simple initial conditions: Potential at the centre is 4 V Potential at the edges is 0 V How would I determine the potential ...
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456 views

Finding Inductance in an AC RLC Circuit?

In the laboratory you find an inductor of unknown inductance $L$ and unknown internal resistance $R$. Using a dc ohmmeter, an ac voltmeter of high impedance, a 1 microfarad capacitor, and a 1000 Hz ...
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341 views

Logarithm of the voltage of the inductor in RL circuit experiment is nonlinear with time

I performed an experiment about the RL circuit, with following circuit: (I used the PASCO RLC circuit lab.) By Kirchhoff's voltage law, (denoting the emf of the signal generator $\mathscr E$, ...
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Are diodes (or FETs) electrets?

The explanations I see of diodes and FETs seem to involve various depletion regions, migration of electrons and holes, and the such. My (perhaps naive) interpretation of these explanations implies ...
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65 views

How to apply kirchoff's laws to motors in DC and AC settings

DC case: is it ok to treat a motor as a variable resistor, with resistance depending on the load? AC case: suppose I have a motor that runs at 120V AC and is rated to X watts, how can I determine how ...
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62 views

What are the first couple terms of the Taylor series for the evolution of this network of capacitors and resistors?

note: This is a computational problem, and I only need approximate accuracy, so the overall goal is, for a given accuracy and $\Delta t$ to compute the state of the system at $t+\Delta t$ to within ...
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96 views

Internal resistance of a battery

It is my understanding that internal resistance of the battery is mainly due to resistance of its electrodes and electrolytes. During the charge or discharge of the battery, there's a potential drop $\...
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337 views

Coupling of LC circuits

I am reading an old article in a physics journal in which the author explains that the frequency between two identical, but capacitively coupled oscillators becomes $\omega_\pm=\omega_0\sqrt{1\pm\...
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72 views

How can the response at the terminal end of an infinite ladder network be solved?

In a recent post: How can the transfer function of an infinite ladder network be used to solve real world problems? I reference how one can solve the transfer function (impedance) of an infinite ...
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If a heater was turned on its' own wire, would heating of the wire cause the resistance to increase, thus the current into the heater to decrease?

I'm thinking not, because; A) It wouldn't make much sense in the real world because you'd need to avoid ever turning a heater towards its own wire, and you'd have to regulate the temperatures of any ...
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112 views

energy conservation in an electric circuit

Define a reactive (lossless) and reciprocal two-port by its impedance matrix $[Z]$, so that $[Z]+[\bar Z] = [0]$ and let the source impedance and open circuit source voltage be $Z_s$ and $V_s$ at ...
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115 views

On resonance of an RLC circuit

How do I prove that the width of resonance in an RLC circuit is the inverse of the proper time of the circuit? I know that the amplitude of charge in the condensator is $$Q(\omega)=\frac{V_\text{max}/...