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

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How soon would electrons start flowing once I closed a switch on a circuit that was one light minute away from the battery

In a circuit, how do electrons "know" when the circuit is closed? To my understanding, they do not start flowing unless the circuit is closed. How soon would they start flowing once I closed a ...
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0answers
16 views

Hollow metallic waveguides versus optical waveguides versus cables

In almost every physics program, you learn about electricity, electromagnetism, photonics, ... Within the electricity course, you learn about transporting electric energy as electrons through cables. ...
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2answers
140 views

What happens in circuits where the propagation time of the electric field is significant?

Kirchhoff's current law assumes "that whenever current flows into one end of a conductor it immediately flows out the other end". I want to understand what happens when we cannot make this ...
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24 views

What happens to the electrons at junction?

In a Closed circuit at any wire junction, one end of a wire is bound to an end of another wire . Now the Circuit is closed. So the electrons are passing through the wire. Now at the junction there is ...
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67 views

Why does the characteristic curve (V vs I) for a light bulb backbend?

When teaching Ohm's Law, I have students do an exploration of a small, incandescent light bulb with a low frequency (1-2 Hz) sine wave. It's a simple series circuit of source and light bulb, ...
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73 views

Speed of electricity in cable [duplicate]

Movement speed of electricity in cable, is same as speed of light in space? In other words, electricity moves in usual electro cable aproximatelly 300 000 km/second ?
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66 views

Why does AC induction motor rotate the same way?

Suppose an aluminium disc is suspended where it can freely rotate. A magnet is placed above (not touching) the aluminium disc and made to spun. This obvious causes a changing magnetic field. By ...
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1answer
37 views

Why does not the electrons in a conducting the wire end?

What happens to the electrons in a conducting wire, Why does not the electrons in the wire end? I have read answers on the web but have not manage to understand, the free electrons from the ...
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1answer
32 views

Can we use a photon to use it as a changing field in an electric generator? [closed]

In an electric generator we use a changing magnetic field to create electricity. But what if we use a photon's oscillation of EM waves to generate electricity in a metal wire as we do in an electric ...
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23 views

Would it be possible to transform power using capacitors instead of coils?

Would it be possible to use capacitors to transform electrical tension (up or down), in the following way? Let's say you have a 10v battery, and you want to transform the tension up to 40 v. First, ...
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1answer
57 views

Why is the resistivity of a copper cable much higher than copper?

I was looking at the data sheet for a copper cable and noticed the conductor resistance to be specified at around 5 mOhm/m. This is magnitudes higher than pure copper, which has a resistance in the ...
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1answer
85 views

Does a Tesla coil work in space?

If I took a Tesla coil into space, and then turned it on near, but not touching metal objects- would charge jump to the metal objects? It's my understanding I wouldn't see a flash, since the lightning ...
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1answer
68 views

Will a small magnet affect an insulated computer wire?

I'm designing something that involves a small magnet, probably about 0.5m in diameter, which will rest next to a computer wire carrying data, video, audio, etc. If the wire is insulated (think USB or ...
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39 views

Capacitors as Energy Wasting?

I am reading a lot of articles about capacitors as the energy storage. Let's consider simple circuitry which contain the battery and capacitor in series. The energy flow from the battery will be ...
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19 views

Electrostatic concept using for dust attraction

Can I use a charged electrode to attract dust particles from any surface? If yes, then surface should be conductve or non coductive? Or any other ways to do this by electrostatic concept.
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0answers
23 views

Electrostatics effect on resistance values [closed]

Consider two parallel metallic plates separated by a silicon dioxide layer of thickness tox (like a capacitor). In this case I am applying a positive voltage to the top metallic plate. Now due to ...
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1answer
25 views

How to configure two infrared light to produce two different intensity

I have two infrared illuminators that have the same properties (same wavelength, same number of leds, same angles, same max voltage and amperage). suppose that these illuminators are attached at the ...
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2answers
47 views

How are superconducting magnets powered?

Since the resistance of a superconducting circuit is exactly 0, it would try to draw infinite current from a power source, since P=I^2*R. For a finite power source, I-> infinity as R->0. Correct? ...
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2answers
109 views

Does electricity have mass?

Given a superconducting magnetic coil, such as the ones at the LHC, is there a difference in the coil's mass when it is powered down versus when is powered up? Edit: This has been labelled a possible ...
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1answer
163 views

Is it possible to explain voltage and current using the wave nature of electrons?

Assume a battery and resistor are connected in a series. If we double the resistance, the current gets cut in half. This is a macroscopic effect. How do those electrons know that resistance has ...
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208 views

how does electricity travel?

I have always wondered how it travels. One thing I do know is magnets are used but I am not sure. The type of devices I mean are ultility poles that carry electricity from the powerplant to a house ...
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1answer
56 views

Finding the resistance of platinum wire [closed]

Im currently lost on solving this potentially simple electricty question and was wondering if anyone in this community could hint me or tell me which equations and why these equations would be ...
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17 views

Electrical conductor in a non-conservative electric field

Does electrostatic shielding hold for non-conservative electric fields? I don't think so, but I cannot explain why. Please help.
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20 views

How does a dynamic electric field change a semiconductors carrier mobility?

Can an electric field that is spatially and/or temporally dynamic affect the carrier mobility in or on a semiconductor and, if so, how and to what degree? I appreciate any help or thoughts you have ...
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34 views

Analytic solution for AC current density in a wire? (skin effect)

As I was reading about skin effect , I realized that the skin depth $\delta$ is defined assuming a plane wave incidence with a flat media and then the surface current is given by: ...
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4answers
68 views

What instrument should I use to vary the power given to a heating element? [closed]

I have a nickel-chrome wire as a heating element and I want to vary the power given to it to control the amount of heating the wire produces. Which instrument should I use? Please don't give ...
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2answers
73 views

Which expression to use for electrical power?

We know that electric power can be written as $P=VI$, or $P=\frac{V^2}{R}$, or $P=I^2R$. But when to use which one? Sometimes two different formulas give different results! Please explain with ...
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What's the conversion of ms^-2 to Watts? [closed]

I'm looking to find out how many Watts gravity would be if it were in Watts rather than ms^-2.
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19 views

The speed of an electrical signal through different mediums [closed]

This is sort of a bio physics question and it comes in two parts. The first is: what is the speed of an electrical signal through human nervous tissue? The second part is: what is the speed of an ...
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1answer
87 views

Why don't get I shocked in an electric shower if the resistance makes contact with water?

I've found this image that perfectly illustrates my shower. I've read somewhere that the resistance is insulated so even if it touches the water, it doesn't conduct. However, as you can see, the ...
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2answers
82 views

Is pure water electrically conductive? [closed]

I know that water with some ions dissolved is a good conductor. I wonder whether it is true for pure water?
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23 views

Could two electrolasers be used as a cutting tool for non-conductive materials like rock?

An electrolaser is an ionizing laser that turns the air molecules in its path to a conducting plasma. There have already been experiments with electrolasers as thunderpoles. You can also inject a ...
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2answers
40 views

Shorting a Superconducting Coil with A/C

When a superconducting coil carrying a direct current is shorted, it continues to carry the current without loss (approximately), assuming it stays cooled and superconducting. What would happen if ...
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2answers
147 views

Why does all the current flow through a short circuit if its voltage drop is considered zero?

Path of least resistance vs. short circuit I know the path of least reisistance has been clarified already However, to derive the equations you need to assume that the voltage of each parallel ...
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1answer
25 views

A conceptual question regarding suspended ring inside vertical inductor coil

Suppose a metal ring is suspended inside a vertical inductor (with an elastic string ) when the circuit is open. When the circuit is closed, does the metal ring tend to jump up or fall down? Why? I ...
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1answer
64 views

Nature Of Bulb Glowing In Parallel LR circuit with bulbs

In the given circuit the switch is initially closed and then opened after some considerable time.Then which bulb will stop glowing first? Which bulb will glow more brightly?Why ? .After opening ...
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35 views

Can volume affect capacitance?

I know the math doesn't support it, but will a solid sphere and a thin foil, both of the same surface area, measure exactly the same capacitance? Do electrons strictly gather on the surface ...
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7answers
9k views

Why does public mains power use 50-60 Hz and 100-240 V?

Is there a physical reason behind the frequency and voltage in the mains electricity? I do not want to know why exactly a certain value was chosen; I am rather interested to know why that range/order ...
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1answer
77 views

Question on Electromagnetic Induction

If a magnet is moving through a solenoid, why is there no electromotive force being induced while the magnet is at the centre of the solenoid? (Is it because emf is induced in both directions?) Can a ...
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41 views

Gauss law for a cylinder shielded by a grounded conductor?

So I am trying to solve the following problem: My approach: Applying Gauss's law on the two regions yields the following $$\mathbf{E}=\left\{\begin{matrix} \frac{\rho _0 \rho ...
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19 views

Could an electrical pulse with the right properties reach a person's head after striking their chest?

I am trying to figure out if it is possible to build an electrical gun that could instantly and reversibly render a person unconscious. The trouble is that the gun should work when aimed at the ...
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0answers
101 views

Why the coil on high tension wires

Today I saw some high tension wires of which some (the middle two) had some large coils wound on top of them as in the image, every 50 meters or so, over a few hundred meters. Does anyone know what ...
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1answer
119 views

Nuclear to Electricity Energy Conversion

Currently nuclear power generates heat, which heats water into steam that turns conventional turbines. The energy conversion is as follows: photonic->heat->kinetic->electric This would result in low ...
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1answer
64 views

Must a universal motor always rotate at the frequency of the AC current?

So here I have a picture of a motor (I think it is a universal motor but I am not sure). My question is if this motor is connected to an A.C. supply, does it have to rotate at the frequency of the ...
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2answers
44 views

Electrons after drop voltage

I know that the voltage between two terminals of a battery causes the electrons to move through the wire, and i also know that the voltage in a circuit is distributed among the number of resistors in ...
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2answers
72 views

Mechanical equivalent to electric circuits

Could one build a mechanical equivalent to electric circuits ? I'm considering mechanical waves (like shock waves) travelling through a medium here. I'm aware that due to the high loss and practical ...
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2answers
109 views

Do electrons always have a probability of being somewhere?

In the same way as when they surround a nucleus? How about when electrons go through wires or are ejected as beta particles? Do they still only have probabilities of being somewhere, or...?
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150 views

Heat generated in Nichrome Wire

I want to do some experiment but I thought I would go over this theoretically before trying out and now I have a doubt. Also, I dunno whether my question is appropriate for this site. I have a ...
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2answers
95 views

Why is an $LC$ oscillator lossless, but $C V^2 / 2$ energy is lost to a capacitor connected to an ideal voltage source?

It is mathematically proven that in an $LC$ oscillation that all the energy gets transferred from the inductor to the capacitor and vice versa. There is no energy loss as there is no load in the ...
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Is there a difference between a ground pin and voltage by an ungrounded plug and just a grouned plug?

I have a cortex dj mixer with an ungrounded plug but with a ground pin (that I don't use for now). But I get a lot of noise if a connect my speakers to this mixer, so maybe I need to ground this ...