# Questions tagged [electric-circuits]

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

579 questions with no upvoted or accepted answers
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### Express Laplace transform of voltage across a capacitor in terms of charge

In Charge Tunneling Rates in Ultrasmall Junctions section 2.1, the authors consider the problem of charge relaxation in a simple circuit shown in Figure A. The implicitly use an assumption made about ...
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### How uniquely determined is the impedance of an infinite-chain circuit?

A recent question asked how to find the impedance of an infinite chain of series-plus-parallel circuits. The standard trick is to split the chain after the first link, and treat the tail of the ...
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### 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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### Temperature distribution in a current carrying conductor

A rod of uniform cross section and composition is connected across a battery. Let the middle part of the rod(when divided into three equal parts) is heated uniformly. A book says that the temperature ...
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### Formulate the equations that describe this transmission-line circuit (Veritasium's circuit)

My question Consider the following circuit. Two non-resistive long transmission lines ($R' = G' = 0 \text{ } \Omega$) , each of the same length $L$ and same inductance per unit length $L'$ and same ...
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### What does the term 'high voltage' really mean?

This might be a dumb question but i am not so familiar with the word voltage: What does the textbooks really mean when they say high voltage?. Does that mean: There are more charges so more voltage, ...
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### 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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### What is capacitance, in general?

In circuit analysis software capacitance can be measured between any two nodes of a circuit or of a multiterminal device. In practical terms we take $C_{ij}$, the capacitance between $i$ and $j$ as ...
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### Salt and electricity

Recently, I did an experiment with salt and electric current. I set up an open electric current in a used battery holder where the missing part of the circuit is two metal plates. I then fill this ...
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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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### 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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### 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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### 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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### Tangential Current of plates in charging capacitor (Function of x)

Suppose we have a capacitor which is charging with applied voltage $(V(t)).$ I want to know what the surface current is which is shown in figure. I know the continuity equation says the current of ...
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### 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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### 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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### With the help of a given charge is it possible to obtain a charge many times greater in magnitude

Consider a spherically conducting sphere. If a charge(say positive) is placed near the sphere, then it will lead to separation of charges inside the sphere.My question is, can we create charges more ...
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### What happens to the resistance, voltage and current when DC passes through saltwater?

I have a circuit of a battery(1.5V or 9V) connected to a multimeter, a connected to 2 metal pieces in water(distilled)(see picture, in place of the LED is a multimeter). With the addition of salt 1. ...
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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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### Current in a diode circuit without a external voltage source

Will there be any current in the given circuit? If current exists then why do they exist and what will be the forward and reverse current and voltage(across the diode)?
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### Capacitance of a thin conducting ring

I am following an exercise in which the capacitance of a thin ring is computed. The ring has radius $b$ and thickness $2a$ where $a<<b$. In this exercise they compute the potential due to a ...
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### Does a higher voltage always mean a higher electric field strength?

In a step-up transformer, the output voltage is higher than the input voltage, while the output current is lower than the input current. Basically, since P = VI is conserved, the current has to ...
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What is meant by "Electrons lose potential Energy" when going through a resistor. In a case of falling from a height you would be at a lower altitude and therefore lower potential but how is ...
I asked this question on QC.stackexchange before, but received no answers and only the advise to post ist here. Thus: In the Cooper Pair box, the conjugate momentum $\hat{n}$ of the reduced ...