Questions tagged [electricity]

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

584 questions with no upvoted or accepted answers
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Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
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1answer
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Do a floor tile or dry sand conduct electricity?

If you touch an electric wire while standing on a ground made of soil or floor tile, you will get electrocuted. So, electricity passes through it. Right? Shall I conduct an experiment by passing ...
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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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1answer
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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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220 views

Lightning through helium gas

Assuming that some distant planet had an atmosphere of helium and(due to extremely cold temperatures) a "water cycle" of neon, what would happen if the theoretical neon clouds acted in a ...
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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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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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2answers
275 views

Spectrum of discharge of air

Where do the various colors in electrical discharge of air with a high voltage originate from? Are these transitions in ionized nitrogen gas or unionized gas? Are chemical reactions involved? I assume ...
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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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1answer
97 views

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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1answer
71 views

What is causing the acceleration of charges in an ideal TEM transmission line?

As I understand, in an ideal TEM transmission line we can set up the telegrapher equations and solve to show that the line propagates voltage and current waves. My confusion arises when we recognize ...
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Stability of a dipole magnet undergoing eddy current braking in a cylindrical tube

Consider a cylindrical dipole magnet with strength $B$ undergoing eddy current braking in a conductive cylindrical tube with the axis of the magnet aligned with the axis of the tube. The magnet ...
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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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What is Electric-flux?

I've searched the question in the forum, and found the following conclusion : - "In electromagnetism, electric flux is the rate of flow of the electric field through a given area. Electric flux is ...
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1answer
62 views

Meaning of potential in a discharging capacitor

I am dealing with this thing I cannot figure out. When a capacitor is discharging, the electric field inside it varies with time so we cannot perform the line integral to determine the potential ...
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266 views

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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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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3answers
170 views

How do we know that a non-rechargeable battery obeys the law of conservation of energy?

For a rechargeable battery, I can show that energy is conserved by Discharging the battery. Measuring the energy required to charge the battery. Measuring the energy I get out from a second ...
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1answer
840 views

How is static charge in insulated shoe soles transferred to a person?

Think of the typical static electricity scenario of touching a doorknob and there is a static discharge. We have an insulated floor, and insulated soles (a nylon carpet and rubber soled shoes). The ...
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194 views

At what distance is lightning dangerous for someone lying down?

My 8 yo child told me that they learned at school that they should lay down flat on the ground in case of lightning. I told him that the more correct position is crouching down with feet together, but ...
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998 views

Distribution of current of a rotating cone

If I have a hollow cone (surface with no bottom cover ) as the one in the picture. The cone has surface charged density $\sigma$. It rotates around the symmetry axis with an angular velocity $\omega$. ...
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How can current flow without voltage?

The following is an image from my school textbook How do electrons travel from E to F is voltage (or the J per C of charge) is zero? I think my issue is a deeper misunderstanding of the nature of ...
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Why did the defected bulb glow brighter when switched off?

Suddenly an LED bulb in my house stopped glowing (actually it was having very little brightness (can be noticed in the video)). But when I switched off the bulb , it first glows brighter and then ...
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Why do lightnings generated by a tesla coil also move upwards?

I was recently watching some videos of Tesla coils, and the behavior of the rays caught my attention. In the picture below, you can see how the coil is emitting lightnings, some of them towards the ...
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What is the cause of triboelectric effect?

When a glass rod is rubbed with a silk cloth, glass rod loses electrons and silk cloth gains electrons. So, glass rod becomes positively charged and silk cloth becomes negatively charged. But why does ...
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Is it possible to overload a thin conductive object with electrons?

A parallel-plate capacitor is a very simple device. To make one, you can take two metal plates, separate them with a dielectric material, and voilà! You have a capacitor. Given a dielectric ...
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Does a power station directly control the supplied power or voltage?

The electric grid's "job" is to provide to the end user a steady sinusoidal A/C voltage with an RMS value of 120 V and a frequency of 60 Hz. (That's in the United States - other countries ...
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Current through a junction of two metals

When a current flows through a junction or a contact between two metals of different conductivities a charge is accumulated in the vicinity of contact. The charge accumulated, I've read, is directly ...
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86 views

Equipotential surfaces for a knotted charge distribution

Suppose we have a compact submanifold $K$ of $\mathbb{R}^3$ with uniformly distributed charge. Neglecting multiplicative constants, the electric potential $\Phi(\vec{x}) = \int_{K} \frac{dK}{|x - k|}$...
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Does electrical sawtooth wave actually produce sinusoidal oscillations at harmonic frequencies?

According to Fourier's theorem, we know that a sawtooth wave can be represented as a sum of sine waves. These sine waves we know as harmonics (in the context of sound). My understanding is that it is ...
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3answers
142 views

What is the significance of direction of current density?

I studied about the direction of current density but nowhere it is mentioned that what is the significance of direction of current density Also I want to know why we used dot product instead of cross ...
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1answer
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Is this hollywood electrocution scenario plausible?

As this question is a serious spoiler, I've written the film title below the photos In the film, a character is sitting on a guardrail in the freezing rain. A high voltage line from a downed telephone ...
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Potential between a metal sphere and spherical shell which are not quite concentric

I have been struggling with this problem for some time by now. An insulated metal sphere of radius $a$ with total charge $q$ is placed inside a hollow grounded metal sphere of radius $b$. The centre ...
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Why are solar panels still efficient with cloudy weather?

Recently I did an experiment in college involving solar panels. I noticed that the weather suddenly changed from sunny to cloudy, however the output of the solar panels dropped only very little. My ...
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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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462 views

Minimum Voltage to Sustain an Arc

I've read that after a plasma channel is created in air, the resistance decreases significantly and the arc can be sustained with a much lower voltage, as long as the heat dissipated by the plasma is ...
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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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1answer
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What is the equation for the electrical arc length of an arc that has been struck?

I have been experimenting with voltages at 2,320 volts AC. I am curious and haven’t found any equation to calculate the electrical arc distance that is drawn after striking an arc by touching the two ...
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234 views

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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1answer
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How to measure a static electric field?

I looked up google but didn't find any design for measuring electric field that doesn't vary with time. My own idea is to use two parallel plates (like a capacitor but without the dielectric). In an ...
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1answer
192 views

Maximum practically possible current value for high frequency alternating current in metal conductor

Is it practically possible to reach 1 A current AC in the metal conductor with frequency 2 GHz? Or in other words, if I have plain metal wire, or maybe a thin tube/foil to reduce skin effect, what is ...
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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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1answer
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Why Mobility Of Thin Film Changes With Deposition Temperature

A metal oxide thin film is a p-type semiconductor (say copper oxide Cu2O) due to metal vacancies in the film. This thin film can be deposited using some form of vacuum/vapor deposition. I know that ...

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