Questions tagged [electricity]

The study of the presence and flow of electric charge. Charges, currents, fields, potentials.

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Drift velocity question

I'm studying about Drude's model. Given that τ is the average time between the electrons' collisions with the ions and the applied electric field is E, we have: $$a=\frac{eE}{m_e}$$ where e is the ...
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Strong force equivalent of electricity?

Could colour charges be manipulated into something analogous to the flow of electricity, and if so, would there be any situation in which circuits of this kind would be useful? For example, given a ...
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How can the effects of temperature be accounted for in-situ electrical resistance corrosion monitoring?

In reading the Berkeley Lab's article Rust Never Sleeps, where research is underway investigating the use of iron oxide rust as a photovoltaic, they state: Rust – iron oxide – is a poor conductor ...
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Can the melting temperature of metals be altered by modifying the local electric charge?

I'm researching a project in which metal needs to be melted. It would be very helpful to be able to reduce the melting temperature to improve the feasibility of the project. I've been looking into ...
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Geometric frustration in power transmission networks

I read this article concerning the detection of Braess Paradox on power transmission networks: http://phys.org/news/2012-10-power-grid-blackouts-braess-paradox.html Here is a quote from the article: ...
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Lightning sprites

Lightning usually occurs due to an electrostatic discharge between an electrically-charged cloud and the Earth's surface, or between clouds. There are also sprites, electrical discharges that occur ...
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If you toss a handful of confetti onto a comb, why does some of it stick and some of it fly away?

My guess is some paper pieces happen to be charged with the opposite charge compared to the comb, so they are attracted, but once they touch the comb, their charge is neutralized. But the comb is ...
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How does a plasma globe work?

I am trying to simulate a plasma globe using computer. But I do not know how to model the motion of its filaments. My first guess is to construct a potential field. And the filaments are the paths ...
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What mechanisms require the use of different polarities in DC welding?

In gas metal arc welding, an electric arc forms between the work piece and a consumable wire, heating the work piece and also melting the tip of this consumable wire, which is continually fed into the ...
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Lightning in space, would it be a perfectly straight line?

I have read this question: Can lightning happen in a vacuum? I do understand that here on Earth lightning consists of electrons moving in space and some of these electrons are tracing path, and ...
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Can you generate 3-phase AC power from linear motion?

If you have reciprocating linear motion (such as a piston moving up and down in a cylinder), is it possible to generate three-phase AC power from it without converting it into rotary motion first? I ...
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Question about action-reaction pair of two wires carrying current in the same direction

Imagine two wires lined up so that they are parallel, and that they both have a current running through them in the same direction. The magnetic field produced by the current of one of the wires (say,...
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Charge and its relationship to Voltage

I was working on a model to describe the voltage between two metal plates (like in a battery) and came up with this model. I wanted to see if my physics and math were right. So I started out assuming ...
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What is all the known information contained in thermal noise?

I've read up a little bit on thermal noise, which is an unavoidable noise in materials when $T>0K$. Thanks to this noise, by measuring the voltage across a material, it is possible to extract the ...
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What is the difference between source current and current induced due to electric field?

I have seen in some places the following expression for current in an electric conductor (for example Peter Monk's Finite Element Methods for Maxwell's Equations, equation (1.8)):- \begin{equation} \...
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What is the physics behind the vibrating feeling you get when you touched an inducted metal surface?

When I was last working on the highway, I stopped to help a motorist parked under high tension power lines. I'm driving a large Ford Transit van, fairly box shaped. My van was parked 90 degrees (...
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Why do ceramic magnets work on touch screens?

I know how our touch screens work by sensing changes in voltage with capacitors, and then pinpointing our fingers location. But recently I was playing with a ceramic magnet on my phone. As I took ...
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Tap water conductivity differences between AC and DC

Direct current is often used in electrolysis and because of the alternating nature of AC, it's not great for electrolysis. Tap water, however, conducts AC really well. But why is that? Why does ...
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Why does an alternator slow down when the 3 phases are shorted?

I'm designing a small wind turbine and noticed that when i short the three wires coming out of the alternator, the alternator is breaking and the blade RPM is dropping. What is the explanation for ...
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Why the changing magnetic flux horizontal component does not induce electricity?

Textbooks just seem to utter that change in the magnetic flux that is 'piercing' the plane contributes to electricity induction. They don't explain why. Is there any intuitive explanation?
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Van der pauw method for an isolated hole

Van der pauw method is a way to measure the resistivity of a material with arbitrary shape while it meets some specifications ( being homogeneous and ...). One of the conditions is that the sample ...
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Circumference measurement using a capacitive sensor

I have a question which I hope someone in here can help me answer. Background: I’m building a device where I intend to use a stretchable capacitive sensor to define the radius change of an object. ...
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Alternative solar panels

I was doing a bit of thinking recently, when I stumbled on an interesting idea. In a simplified sense, solar cells function by absorbing light and converting it into electrical energy. Since visible ...
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Drift velocity of electrons in a superconducting loop

Do electrons travel at the Fermi velocity in a superconducting loop? For metals the Fermi velocity seems to be around $10^6$ m/s. So would electrons (in a Cooper pair) travel around the loop at this ...
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Why Transmission of electrical energy without wires was not practical even after Tesla's proposal

Why we couldn't transmit Electricity wirelessly even after so many proposals available proposed by Tesla ? Tesla tried to generate more interest in Wardenclyffe by revealing its ability to ...
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Calculating Electric Field from a Potential Difference w/o Charge

So here is my homework question: Two long cylindrical shells of metal (radii $r_1$ and $r_2$, $r_2 > r_1$) are arranged coaxially. The plates are maintained at the potential difference $\Delta\...
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Current between supeconducting rings

How to calculate the current between two superconducting rings with radius r separated by a distance d? Please note that being unfamiliar to the concept of superconducting rings, I can't approach ...
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Schottky and shot noise

I am looking for a little history on shot noise: when was it first predicted and first measured? In particular, what was the role of Schottky? His 1918 paper "Über spontane Stromschwankungen in ...
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Joule's heating effect

Can we derive joule heating effect or heating of current using energy conservation for electrons when current is varying with time ?Like using concept of drift velocity,potential diffrence across ...
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Experiment interpretation. Dielectric polarization/triboelectricity/other?

My aim was to create a relatively strong electrostatic field to experiment with biological systems. So, I built a kind of "sandwich" made of a plate of aluminium surrounded by two 4mm plates of ...
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Measuring electrical conductivity on a liquid

I would like to measure electrical conductivity on water with minerals on it, I understand I should be placing two electrodes on the water with a given current and distance between them, how can I ...
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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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Introductory Electricity and Magnetism Textbook for Biology and Biophysics

My research advisor will be teaching a new course at my university on Electricity and Magnetism for Biophysics and Biology students. This is the first course the students would be taking in E&M. ...
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Speed of electron and proton in electric field

Speed of electron and proton in electric field. In a uniform electric field E, the acceleration of an electron in vacuum is 1836 times that of a proton (proton/electron mass ratio is 1836). I'll like ...
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Why is the charge of this surface specified?

I am working on a problem where I have a conducting disk and a point charge above it and I must describe the charge density throughout the disc. What confuses me is that my result seems to specify ...
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During a lightening storm is it significantly more dangerous to be in a body of water than on land?

Most people think that if you're in a body of water and lightening strikes the water anywhere near you, you instantly die. Is this true? (I'm almost certain it is not true.) So in general, I'm in a ...
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How much electricity does it take to create hydrogen from water depending on the water's pressure?

Imagine creating bubbles of hydrogen and oxygen underwater at a particular depth using electricity. Then reusing the energy of the bubbles going upward to the surface ( buoyancy ). How is the energy ...
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Electrical resistivity calculation of a cylindrical material

I have a copper rod, its diameter is 13mm, and its height is 13mm. I want to check its electrical resistivity. I have tools to give this copper a constant current by two points (the two black dots in ...
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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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Understanding the collisions of electrons and ion cores in the Drude model

In the free electron gas model, we assume that the conduction electrons are assumed to move freely throughout the conducting material which collide with the ion cores of the lattice. Image taken from ...
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can we use electrical discharge to remove dust on ceiling fans?

I heard that dust accumulates on ceiling fans because of static electricity. Can we "Un-cling" the dust particles, so that it is easier to clean?
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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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EMF developed in a varying magnetic field

Let's say there's a cylindrical varying magnetic field (varying at a constant rate) and I have a conducting body, let's say a rod placed in a plane perpendicular to magnetic field. I am having a ...
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Fringing fields for capacitor with dielectric

I have read the report Fringing Field Effect in Electrostatic Actuator by Vitaly Leus and David Elata. In this report, they present analytic methods to calculate the capacity of a mems device ...
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Explaining Lenz's law?

This example given bellow intrigued me, since it is really simple but I still can't find it coherent with experimental results. Description : We have a static magnetic field pointing in the $\hat{x}$ ...
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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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We know that the earth has charge of -500,000 C experimentally or by equations?

I don't understand how we get this value and what it means, does it mean that this charge distributed over earth surface so charge density is small? Or it distributed over the volume?
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Conductivity and free/bound charge for conductors, insulators/dielectrics and semiconductors

I am slightly confused about the distinction between these three types of material in terms of a) conductivity b) the idea of free and bound charge If we consider the distinction between these in ...
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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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Quartz piezoelectric battery

I'm designing a battery that uses quartz crystals to hold/produce a current for a long time using piezoelectricity. My question is: Would it be more efficient to have multiple small quartz crystals ...