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

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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
67 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
71 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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32 views

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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1answer
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
79 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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21 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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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
136 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
60 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
76 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
118 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
70 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
106 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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143 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
90 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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0answers
18 views

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 ...
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26 views

Does a variac vary the current as the voltage is varied?

I used a variable transformer in an experiment hoping to vary the current in the setup. I used Ohm's law to calculate the current at each voltage. I am thinking this is the correct approach, but i ...
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2answers
95 views

How does crystal lattice explain electrical conductance?

From http://education.jlab.org In a metal, the atoms are arranged in a crystal-like configuration. ... Now, in a metal, the valence band is relatively close to the conduction band - ...
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37 views

Energy conservation applied to a generator

If a turbine runs with a kinetic energy of some joules, the electricity produced must also have the same power given out, according to the energy conservation law. Now if the electric flux is ...
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3answers
1k views

Difference between live and neutral wires

In domestic electrical circuits, there are 3 wires - live, earth and neutral. What is the difference between the live and neutral wires? As there is AC supply, it means that there are no fixed ...
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57 views

Disk Free falling in magnetic field

A circular metal plate starts falling from rest in a region of uniform magnetic field "B". B is parallel to the plane of plate and to the surface of earth(refer to diagram).The plate has mass "M" ...
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2answers
436 views

What's the difference between a positive and a negative current?

Say I have a wire, and I connect a current source on its left end, and a ground to its right end. Then using my power supply I source a positive current, does this mean that electrons will move from ...
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41 views

Why does this electrometer works?

I was looking at this electrometer (measure of static field E). The principle is : E moves electrons between the 2 electrodes into the coil and there is a magnetometer inside the coil. This ...
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35 views

Flow of charges in two different materials

Consider two cylindrical conductor rods as Copper rod and aluminium rod. Their edges are in contact,that is their circular faces are in contact. Their other edges are connected to some DC voltage. And ...
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1answer
87 views

How to solve difficult resistance puzzles? [closed]

How does one solve really difficult resistance puzzles? These are presented in the form of a diagram with multiple resistances in various combinations. I have done some puzzles by reducing the puzzle ...
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29 views

How do you calculate the brightness of an electronic arc through a gas?

Quick question: I want to model the brightness of a xenon flash tube when a capacitor is discharged through it, but I can not find any equations related to this. It only has to be a rough model, just ...
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1answer
76 views

What does electrically charged mean?

So I was reading my physics textbook and it said that "Suppose we have two metal spheres, one highly charged and the other electrically neutral." What does it mean by highly charged? Does that mean ...
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1answer
29 views

Radioisotope beta decay generator

Why are there no electrical generators utilising the electron/s of beta decay from a radioisotope for generating a working current? For example, how much radioisotope would I need to generate 1A or ...
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3answers
74 views

Why is the total potential difference in a circuit the sum of the individual potential differences?

I am having difficulty in applying my understanding of electrical potential to circuits. Why is the total potential difference in a circuit the sum of the individual potential differences among ...
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2answers
75 views

Velocity of an Electron as it Passes through a Uniformly Charged Ring

I've been presented with a problem in which an electron is placed a certain distance x from the center of a positively charged ring and allowed to move freely. The ring has a known charge density λ. I ...
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1answer
59 views

Does magnetic induction produce potential across zero resistance wire?

If magnetic field is increased at a constant rate inside a zero resistance wire loop, then, according to Faraday's law , $$\varepsilon = \frac{dΦ}{dt} $$ Thus, a potential difference is produced. ...
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64 views

Magnetic ball Inside a rolling hollow copper sphere?

Just curious with regards to the production of electricity. What would happen if you put a magnetic ball inside a hollow copper sphere and rolled it down a hill? Where would current be generated ...
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3answers
3k views

What causes electrical boxes to hum?

Often times you pass by an electrical box on an electrical pole and you hear a distinct hum emanating from it. What causes that tone? Does the flow of electricity itself have a sound? Or does the flow ...
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1answer
42 views

Negative Electric Capacitance

I know electric capacitance is always positive (otherwise it doesn't make any physical sense). But the capacitance is related to the potential difference, which can be positive or negative, depends ...
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2answers
95 views

Is wearing metal armor during lightning safe?

I recently saw in a television show that wearing a metal armor during lightning is good because metal provides the path of least resistance for electricity to flow to the ground. Now my question is,is ...
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1answer
144 views

Why did LED lit up while soldering? [closed]

I was soldering an LED when accidentally the soldering wire touched the LED's other Pin while the soldering iron was touching the other and the LED lit up, not bright but bright enough to be seen. I ...
2
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1answer
113 views

A working “mechanical” model that explains current in a wire/circuit?

In class we learned about point charges, electrostatic force, voltage, current etc. and discussed circuits along the way. Now problems arise when I try to apply the learned concepts to explain how ...
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1answer
116 views

Electric field outside conductor with cavity

Recently I heard a lecturer claim that the electric field outside a solid conductor containing a cavity with a point charge $q$ at a point $\mathbf{r}$ is the same as the electric field due to the ...
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2answers
483 views

What makes Human a Conductor

Conductors, are those which have free electrons... and because of this have same electric potential all over. But considering our body, which has many electrical voltage, current signals passing by in ...