Questions tagged [electricity]

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

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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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3answers
540 views

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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122 views

Why do clothes produce sounds after being in front of a computer for a long time?

Quite often, after sitting in front of the computer not moving a whole lot for a long time my upper body clothes (usually sweaters) make soft crackling sounds when moving or specially when taking them ...
4
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1answer
596 views

My fingers are sparking large source of electricity when I touch plastic boards covered with polythene

Still I don't understand why am getting such voltage & it's the same feel that I touched 250 voltage of current. Also when I put two fingers on opposite direction (when I am removing polythene ...
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0answers
809 views

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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0answers
67 views

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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0answers
78 views

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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1answer
220 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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183 views

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 ...
4
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1answer
90 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
85 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 similar way ...
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0answers
78 views

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 ...
3
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1answer
100 views

Are Electrons in a Circuit Subject to Newton's Third Law?

Consider a simple electrical circuit made up of a battery, an incandescent bulb, and wire. The battery and bulb are equal in mass and are on opposite sides of a circle made up by the wire. Lastly, the ...
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0answers
93 views

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 ...
3
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2answers
290 views

Can induction coils heat air?

I understand that induction coils can heat up conductive materials such as metals, but I'm wondering if they can heat up normal air. And if they cannot, can ionizing the air beforehand allow it to be ...
3
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0answers
80 views

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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118 views

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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0answers
1k views

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 ...
3
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1answer
61 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 ...
3
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0answers
225 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 ...
3
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0answers
121 views

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 ...
3
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1answer
613 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 ...
3
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1answer
804 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 $\omega$. ...
2
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1answer
56 views

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 ...
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0answers
31 views

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 ...
2
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0answers
32 views

How do I check to see if a nonrechargeable 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 discharge....
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59 views

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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0answers
77 views

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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0answers
25 views

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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68 views

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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0answers
178 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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36 views

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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2answers
55 views

Is the potential difference mathematically based on average?

Consider two electrodes with non-uniform compositions. Therefore, the distribution of the electric potential is not uniform across each electrode. Is the potential difference between ...
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0answers
67 views

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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685 views

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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1answer
638 views

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 ...
2
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1answer
95 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 2GHz? Or in other words, if I have plain metal wire, or maybe thin tube/foil to reduce skin effect what is the ...
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0answers
107 views

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
96 views

Does there exist a rigorous general mathematical proof for $M <\sqrt{L_1L_2}$?

Does there exist a rigorous general mathematical proof for $M <\sqrt{L_1L_2}$? Here $M$ is the mutual inductance between two conductors and $L_1$ and $L_2$ are their respective self-inductances. (...
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0answers
708 views

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 ...
2
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1answer
170 views

How much is an incandescent lamp's filament stressed by an on/off cycle?

The coiled tungsten alloy filaments of incandescent heat up greatly in use. Eventually, they fatigue and fail. Lightbulbs are rated by an number of hours of use, but along with the lit hours and any ...
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0answers
54 views

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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0answers
57 views

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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1answer
33 views

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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1answer
325 views

Why is lightning going from the Earth to the clouds while the electrons are going from the clouds to the Earth?

The lightning is often a discharge in advance. The (negative) charge slide occasionally a little further on in the conductive channel, wherein said channel is highlighted each time something. The ...
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129 views

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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1answer
155 views

Difficulty understanding the energy transformations during resistance in a circuit

I am currently having problems understanding the energy transformations that occur when resistance in a solid conducting wire restricts current flow. From my understanding, resistance in a solid ...
2
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1answer
99 views

Electron Flow Notion

I would like to ask something that bothers me. A lot of us know of the electron flow notion, which it is the technical representation of how the electron charge really flows, starting from the ...
2
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1answer
130 views

Doppler-shift of AC-electricity

A tram is powered by overhead wire, the wire has alternating voltage of 1000 V RMS, the frequency of the alternating voltage is 50 Hz. The rails are the other wire. The tram is moving at speed 100 m/...
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0answers
418 views

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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