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

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Balloon rubbing; where do the electrons go?

If you rubbed a balloon with a towel, where would the electrons go: the balloon or the towel? Why? I'm guessing the electrons would go to the object with a larger mass, but it's just a guess. :)
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266 views

What causes the electrical reaction between two carbon rods touching?

I recently watched this video in which carbon rods from a 6V lantern battery are removed and then touched together to create a makeshift arc reactor furnace. This produces electrified plasma which can ...
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276 views

Why does my shirt make a crackling noise when it is static?

I thought that when clothing becomes "static" (used as a colloquial adjective for that state when clothing fresh out of the drier sticks to everything) it's because of a build up of electrons. That's ...
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Why does an electric motor burn up when you physically stop it?

As an electric motor spins, the energy from the electricity is 'conducted' to the rotor by the magnetic fields. However, when the motor is stopped, the energy becomes heat and burns up to motor. ...
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438 views

Batteries and voltage?

The voltage of a battery gives you the difference in potential energy 1C of charge would have at the positive terminal vs the negative terminal. If I connect a wire to both terminals, the battery ...
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172 views

Applicability of the concept of voltage in electrodynamic circuits

In electrostatics, we have $$\nabla \times \vec{E} = 0$$. Hence, we can define a scalar potential $V$, where $$\vec{E} = -\nabla V$$. We know from Faraday's law that $$\nabla \times \vec{E} = ...
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1k views

Speakers and Static from Hands

Why is it that when you touch the a bare male end of a speaker feed that the speaker makes hissing noises? Is it just (eddy?) currents running through you?
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6k views

Using Electrostatic Force to Repel Dust From an Object [closed]

I have two 4,000V, 2.5mA, DC power supplies and am attempting to use them in such a way to cause a 6x4x1-inch ABS plastic object to repel dust from the ambient air and prevent this dust from settling ...
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1k views

Does light induce an electric current in a conductor?

I know that electromagnetic waves induce electric currents in conductors and that's the basis for radio, wi-fi etc. I also know that light is also an electromagnetic wave. So, can light induce a ...
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224 views

maximum positive electric charge of solid body

What are the limiting factors on the positive charge of a solid body? If I assume a 'perfect insulator' environment that would not exchange charge with my solid body, I would guess that I can remove ...
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590 views

Algorithm of Lightning Strikes? [duplicate]

Given an array of charge for a given area (2D or 3D), what algorithm would describe the path that lightning takes? An example algorithm would be from the highest charge of the cloud, find the lowest ...
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174 views

Why an inductor parallel with a light bulb makes it flash as a key closes the circuit?

The title is a simplified form of my question. To be precise, I'm talking about the following circuit: The inductor has a resistanse equal to the resistor in the circuit. So, the question is that, ...
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Why is there no current flow when i connect two opposite terminals of two separate batteries

I don't understand this..maybe there is something wrong with my understanding of battery or electricity. I am learning about electricity more deeply this time. So please spare with me... So lets ...
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135 views

Thermal conductivity affected by electrical current

Does anyone know of any materials whereby the thermal conductivity can be changed by passing an electrical current through the material?
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236 views

Graph of Electrical Resistivity of Air vs Air Pressure

I've search many place ( Google, forums etc ) but can't seem to find anything that explains the Relationship between: Electrical Resistivity of Air vs Air Pressure Constant Variable: ...
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342 views

If atoms have specific energy levels, why do opaque solids absorb all visible light, not just some? [duplicate]

Here's my question: if atoms have well defined energy levels and those differences correspond to the frequencies of light that can be absorbed, how is it that opaque objects absorb all or most visible ...
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177 views

What exactly is ''electric energy''?

If the two fundamental types of energy are kinetic and potential energy, is electric energy simply the kinetic energy of charge carriers? Also, is the statement "A cell converts chemical potential ...
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671 views

If the current is increased, is there more charge flowing or is it moving quicker?

Problem Current is the amount of charge that is flowing through a component per unit of time. For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must ...
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211 views

Question on static electricity & electron transfer

Static electricity is caused by the transfer of electrons between substances right? For example, take a balloon and your hair. Both are stable and electrically neutral. So why would electrons jump ...
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623 views

What determines how much electrical charge an object can hold?

What determines how much electrical charge an object can hold? Does increase voltage force more electrical charge to be store in an object (Van de Graaff generator), since electric field increase as ...
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99 views

How to get a function for the voltage across a capacitor connected to an AC voltage source? [closed]

I am looking for the way of obtaining a solution for $V_{c}$ ,as a function of $t$ depending of $\omega$, of the following differential equation related to an electrical circuit involving a low-pass ...
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22k views

Why is stainless steel a poor conductor of electricity?

I recently had a metal plate put in my shoulder and was wondering why stainless steel isn't a good conductor (At least I hope it isn't). Does the alloy just lack free electrons? Why is that?
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234 views

What happens to this potential energy?

Let's say I turn on a Van de Graaff which creates a large positive charge. Now let's say I have an object with a positive charge in my hand and I start walking toward the Van de Graaff from $x$ meters ...
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897 views

Neon lamp: minimal breakdown voltage

I am looking at this formula from wiki for breakdown voltage in gas discharge lamps, and I see its linear by length (d) (oops, I see it's divided by $ln$) $$\frac{Bpd}{\mathrm{ln}\ Apd-\mathrm{ln}\ ...
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110 views

Superconductors and electrical fields

I have been looking around to figure out how superconductors are made. What ways are there to create a superconductor that don't involve a coolant like liquid nitrogen? Is it possible to cause a ...
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What is the source of high-frequency squeal in faulty CRT monitors and TV, and what is physics of generating this sound?

Sometimes old faulty CRT monitors generate nasty high-frequency squeal sound. What element might be responsible for generating such sound? I have heard that it might be dry electrolytic capacitor; ...
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Potential difference (PD) and electromotive force (EMF) in terms of electrons?

I am trying to understand potential difference and electromotive force in terms of electrons. In the above 3 circuit diagrams the red shows (what I think to be) the distribution of electrons ...
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220 views

Why can't an excess of electrons or holes by themselves cause current flow?

I am a beginner in electrical engineering. Often times (most cases actually), the underlying physics aren't really explained to us and we are just left to assume that it works "because it works." This ...
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334 views

DC current in ideal conductor and skin effect?

I know that the skin depth derived for AC current goes as $$\delta \propto \sqrt{\frac{1}{\omega \sigma}}$$ where $\omega$ is the angular frequency of the field and $\sigma$ is the conductivty. Now: ...
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225 views

Electric arc due to static discharge in a T-Shirt possible?

Yesterday, when I came home, I went to the bathroom (lights off) and i took off my T-Shirt (100% cotton) which I wore under a Shirt (50% cotton, 50% polyester). I believe to have seen a small but well ...
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595 views

(Why) would unmaintained water heater use more electrical energy?

I'm specifically thinking about lime/sedimentation at the bottom of water heater, and calcification of heating elements (and not possible thermal insulation deterioration). It is very often claimed ...
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149 views

How do test lights (mains tester) work?

I was wondering how one-contact test lights work. Obviously there is a small current running from an energized pole through the human body somewhere that is still large enough to produce a visible ...
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210 views

Why do power lines buzz more when it is low-humidity outside?

I have observed that the power lines buzz louder when there is less moisture in the air. Why is this? If it will help the lines are located on the foot hills of a nearby mountain.
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488 views

Why does hair stand up when standing under power lines?

My initial guess would be the immense electric field around the lines, that causes hair to get charged and due to each hair having the same charge they start to repel each other. So what is exactly ...
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lifetime of a PN junction in a diode

diodes are made of silicon, which have been enriched in phosphorus and boron to create the PN junction. Since the electrons are always going in the same direction, from N to P in the junction, I was ...
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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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574 views

What happens when you pass a current through a coil made of a ferromagnetic substance?

I know when you pass a current through a length of copper coil or a solenoid, there is the induction of a magnetic flux. But what of the coil made of the ferromagnetic material, the permanent type ...
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Why are downed power lines dangerous?

A friend of mine was telling me about a storm that knocked down a power line over at their place, and it got me to thinking. Why are downed power lines dangerous? I don't see any good reason for it. ...
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598 views

number of electrons my laptop uses in a second

in order to confirm whether I understand the relation ship between amps, columbs and electrons I decided to try out the following. my laptop adapter's label reads 3.34 amps. I assume that: amps are ...
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Does a capacitor ever get fully charged?

The time $t$ taken by a capacitor of capacitance $C$ in a charging circuit with a resistance $R$ in series with it to accumulate charge $q$ is given by the equation $$t = \tau ...
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Why don't positive charges move?

Charge is carried by electrons moving. The protons are always stationary. The answer I found online is the protons are stuck in the nucleus so they can't move ("strong nuclear force"). But why can't ...
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What is a virtual ground?

What is a virtual ground? I would like to know what it is.
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3k views

How much energy was consumed when we turn on/off light?

My parents told me to turn off the light when I am not using it. But I remember my physics teacher told me that the action of turning on/off a light can cause huge energy. I am wondering how much is ...
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Will adding heat to a material increase or decrease entropy?

Does adding heat to a material, thereby increasing electrical resistance in the material increase or decrease entropy? Follow up questions: Is there a situation were Heat flux ie. thermal flux, ...
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35k views

Would you die if you put your hands on a powerline?

You know how birds perch on powerlines without getting electrocuted? What if by some chance that I find myself falling and I grab on one of them? Let's say both of my hands are on the same line, would ...
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Can electricity flow through vacuum?

People say yes, and give a wonderful example of vacuum tubes, CRTs. But can we really say that vacuum (..as in space) is a good conductor of electricity in a very basic sense?
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Power dissipation in circuits:Why is high voltage used in power lines?

I know this question has been asked before, but there is one doubt I still cannot clear. Power dissipation is proportional to $I^2R$. Does this not mean that it is also proportional to $V^2/R$? If ...
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2k views

How can two different 12V batteries have different amperage for same resistance?

My local car parts dealer presented me his inventory of car batteries. One 12V battery had a 'cold crank amperage' of 600amps. The other 12V battery had a 'cold crank amperage' of 585amps. ...
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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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Why wire filament shakes inside a light bulb?

My light bulb cast a clear light toward adjacent wall and I can clearly see, that wire filament inside bulb shakes, though lamp itself does not moves even an inch What is causing this? Is it a ...