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

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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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1answer
420 views

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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A circuit with no voltage difference, but current flowing

From Michael on Skeptics Stackexchange: How about a wire that's grounded? Safe to touch, right? WRONG. ...
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4answers
2k views

How do electrons “know” to share their voltage between two resistors?

My physics teacher explained the difference between voltage and current using sandwiches. Each person gets a bag full of sandwiches when they pass through the battery. Current = the number of people ...
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5answers
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Why can different batteries with the same voltage send different currents through the same object?

According to an answer in this thread on Skeptics: If you take one of the little 12V garage door opener batteries and short out (directly connect) the two terminals with a piece of wire or ...
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944 views

Salt water conduction

Does salt water conduct mostly by the ions travelling through the solution, or by electrons collectively flowing or hopping through the solution like in metals?
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251 views

determination of voltaic cell voltage

if i understood this correctly, the determination of voltage for a specific voltaic (gallvanic) cell is determined only by the chemical correlation between the two metals. is this true? for an ...
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4answers
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Do Alkaline batteries, $\mathrm{NiMH}$, rechargeable alkaline, Lithium $\mathrm{AA}$, all have similar MAX POWER?

So in physics, one smart teacher told me, $$ V = IR $$ or $$ I = \frac{V}{R} $$ but it is not always true, because $P = VI$ and each power supplying device (such as battery) has a "maximum power" it ...
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550 views

Can electricity transfer radioactivity?

If a cable used to power something is exposed to a radioactive source will it over time make the entire cable radioactive?
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2answers
1k views

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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0answers
261 views

What happens if I charge a a Li-ion battery with non-nominal voltage?

Suppose that I have a li-ion battery with voltage 10V (and some capacity, say 1000mAh). Can I charge it completely using 5V voltage? What will hapen if I charge it with 12V voltage? Edit: Found the ...
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5answers
885 views

How long would it take for electricity to flow from one terminal to other, via a 1 LY long wire?

Basically, how long does it take for electricity to determine there is a closed circuit and how does it know that the circuit exists? I'm curious to know how it knows there is a closed circuit at any ...
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1answer
100 views

Physics II Video Courseware Recommendations

I'm looking for something to supplement my Physics II class. Last year I started using these video lectures to supplement my Calculus class and it helped tremendously. I also turned to this ...
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1answer
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How fast do electrons move through a conductor?

If I apply $1 \text{ V}$ across a $1 \text{ }\Omega$ resistance, I'd get $1 \text{ A}$ flowing. $1 \text{ A}$ is defined as $1 \frac{\text{C}}{\text{s}}$, and $1 \text{ C}$ is equivalent to ...
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6answers
11k views

Difference between current and voltage sources

I am confused about the current and voltage. My intuitive example would be that of a pipe of say water. The diameter of the pipe determines the amount of water flowing per second but the pressure is ...
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8answers
18k views

Electricity takes the path of least resistance?

Electricity takes the path of least resistance! Is this statement correct? If so, why is it the case? If there are two paths available, and one, for example, has a resistor, why would the ...
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3answers
2k views

Why does my body accumulate charge?

If I wander outside in cold weather for 10-20 minutes my body accumulates charges. I get electric shock if I touch metal, e.g., door knob, car door etc. Now I've two questions: Why does human body ...
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3answers
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What happens when we connect a metal wire between the 2 poles of a battery?

As I remembered, at the 2 poles of a battery, positive or negative electric charges are gathered. So there'll be electric field existing within the battery. This filed is neutralized by the chemical ...
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2answers
312 views

how does a glow lamp work

First, what do you call this in English? Second, how does it work? Why do I have not only light at the gas barrier between the two wires? Thanks!
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4answers
2k views

Resistance between two points on a conducting surface

Suppose we have a cylindrical resistor, with resistance given by $R=\rho\cdot l/(\pi r^2)$ Let $d$ be the distance between two points in the interior of the resistor and let $r\gg d\gg l$. Ie. it is ...
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2answers
807 views

Electric potential in a capacitor

Im a writing a school report regarding the electric energy and potential of a capacitor. In short: An experiment was carried out where we charged a capacitor, and then decharged it with an electric ...
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8answers
33k views

How to avoid getting shocked by static electricity?

sometimes I get "charged" and the next thing I touch something that conducts electricity such as a person, a car, a motal door, etc I get shocked by static electricity. I'm trying to avoid this so if ...
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4answers
10k views

Electrical force vs gravitational force

Given that the electrical force is so much stronger than gravitational force at atomic levels, why is it that it's the gravitational force between you and the earth that keeps you on the ground rather ...
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4answers
223 views

Calculating electric field

This problem is giving me a lot of problems. So $E=k*q/d^2$. We'd want to find the distance from q1 to P, which is .1 meters (not cm) using pythagorean thereom. So we know k, which is just $9x10^9$ ...
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Transfer function of an RLC circuit

I'm trying to simulate an RLC circuit using transfer function. Circuit is there: http://i.stack.imgur.com/MC8ME.png (I'm a new user therefore I cannot post images) But I can, L.Motl... Main ...
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2answers
2k views

Special designs to reduce the electrical resistance of a wire

The numerical simulation of this nerdy question shows that the resistance decreases with the number of nodes along longest side, and converges to a finite value when the # of nodes approaches ...
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1answer
20k views

Laptop self charge cable? [closed]

Ok this is a really silly question, but I was really curious as to why this wouldnt work. I'm just starting my electricity and magnetism course, so I really dont know much about electricity. I know ...
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1answer
731 views

does current product push or pull effect [closed]

Since i was a child i was told that current has pushing or pulling effect. However, i never got a dc shock and i don't remember ac shock (i got it very long before). The day before yesterday, an ...
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6answers
20k views

Why does my wife's skin buzz when she's using her laptop?

When my wife uses her laptop, if I touch her skin, I can feel a buzz. She doesn't feel the buzz, but she can hear it if I touch her ear. So I'm guessing it's a faulty laptop, and she's conducting an ...
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2answers
17k views

How does load affect frequency on the power grid?

This story about the use of battery/freewheel based Frequency Regulators confused me about how the 60hz frequency of the North American power grid was set--saying that it was kept at that frequency by ...
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2answers
4k views

What is the Power Consumption of a desktop computer? [closed]

I read an article which tells power consumption by many devices. It say that a desktop computer (computer and monitor) use 400 to 600 watt. While when i checked my computer and monitor with meter, it ...
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3answers
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Why are materials that are better at conducting electricity also proportionately better at conducting heat?

It seems like among the electrical conductors there's a relationship between the ability to conduct heat as well as electricity. Eg: Copper is better than aluminum at conducting both electricity and ...
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11answers
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Does 'electricity' have mass? Is 'electricity' tangible?

Background: I'm in a legal academic discussion about the status of electronic 'goods' and whether they qualify as 'goods' in the same way a chair and a pen do. In this context (and specifically at the ...
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4answers
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Is a signal traveling through fiber faster than a signal traveling through copper?

Does the transmission medium affect the speed of a signal? For instance does light traveling through a fiber cable get a bit from A => B faster than copper can transmit a bit the over the same ...
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2answers
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What is the difference between induced and motional emf?

At least from their names, it seems motional emf is induced, so what's the difference?
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1answer
1k views

Current from induced emf

If the induced emf in a circuit is negative, and current from this emf is the emf over the resistance, what happens to the negative sign in the induced emf when solving for the current? Surely there's ...
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4answers
3k views

Is there a travelling speed of for electric field? If yes, what is it?

Consider a conducting wire of 1M and 1000KM. Now if we connect a battery and a bulb to both these wires. Bulb glows instantaneously its because (my guess:) electric filed travels from positive ...
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2answers
2k views

Does Tesla's photoelectric “solar cell” really work?

Tesla patented a device for gathering energy from light, using the photoelectric effect. (US 685,957 - Apparatus for the Utilization of Radiant Energy): Basically just a sheet of "highly polished ...
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2answers
186 views

How to get the cosine of a waveform?

I have a set of samples that represents a waveform. This waveform resembles a frequency modulated sinusoidal wave (only it is not). I would like to invert this waveform or shift it by $2\pi$ shift it ...
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2answers
733 views

How is electrical energy transmitted?

My original question was in an effort to understand the electrical analogy to Markov chains, which is explained in Snell's article. There are some neat parallels that involve taking a Markov chain ...
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3answers
543 views
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6answers
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Lightning strikes the Ocean I'm swimming in - what happens?

I'm swimming in the ocean and there's a thunderstorm. Lightning bolts hit ships around me. Should I get out of the water?
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1answer
158 views

Amount of 2 amperage [closed]

I have 2 equation describing the alternating amperage $I_1$ and $I_2$. I need to get amount of these amperages. My equations: $$I_1=10\sin(\omega t+30)$$ $$I_2=20\sin(\omega t-50)$$ How can i make ...
5
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4answers
644 views

Help fill in my understanding of the Polywell fusion reactor

Polywell is a proposed new type of fusion reactor, which is designed to use magnetic fields to overcome the problems with the Elmore-Tuck-Watson fusor. I'm trying to understand exactly how it works. ...
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2answers
344 views

Maxwell equations: how to know the behavior of charge and current?

In school-level tasks, when (almost) all substances are linear, homogeneous and isotropic, we have $D=\epsilon E$, $H=B/\mu$ and thus Maxwell "in material" equations (1) say how $E$ and $B$ depend on ...
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1answer
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What’s the relationship between thermal radiation and Johnson thermal noise?

All objects above absolute zero emit radiation due to random collisions between the atoms they are made of. The spectrum of radiation emitted varies according to the temperature of the object, I ...
7
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5answers
533 views

Why were the SI base quantities chosen as such?

The reasons for choosing length, mass, time, temperature, and amount as base quantities look (at least to me) obvious. What I'm puzzling about is why current (as opposed to resistance, electromotive ...
43
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2answers
19k views

Why don't electric fish shock themselves?

Fish like electric eels and torpedoes have specially designed nerve cells that allow them to discharge hundreds of volts of electricity. Now, while pure water is usually nonconductive, the dissolved ...
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7answers
1k views

Is electricity instantaneous?

My question is basically what exactly is electricity? I've simply been told before that it's a flow of electrons, but this seems too basic and doesn't show that electricity is instant. What I mean is ...