# Tagged Questions

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

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### How to calculate required current and specifications for a “wet coil” to generate x Tesla of magnetic field?

A water management project requires a "wet coil" (coil will be submerged in aqueous media) designed to generate a steady-state electromagnetic field of adjustable magnetic magnetic flux density at the ...
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### A problem concerning the force between currents or moving electrons

Concerning two identical wires carrying the same current (same direction, speed and magnitude), they will be attracted because of the Ampere force. But when I was in the frame moving with the same ...
6k views

### Does Fire Conduct Electricity? Why?

Recently, I have stumbled upon a YouTube video by Veritasium describing the conductivity of fire. My question is: how exactly does fire conduct electricity? I am a high school student; therefore ...
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### Confusion about P=VI and V=IR

If we look at $P=VI$, we see that if the current doubles then the potential difference is halved but this doesn't seem to make sense according to $V=IR$. If we look at that equation, since the ...
429 views

### Electromotive force

EMF is defined as: "The potential difference across the terminals of a battery or dry cell when it is giving no current to the circuit." So, if current starts to flow from the ...
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### How do bits get transferred over a copper wire?

I've been a programmer for a while, and I've done a little bit of network programming, but I'm wondering, how do bits get transferred over a copper wire? What counts for a 1 & what counts for a ...
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### Are square wave really square or are they always relative approximations using harmonics

I'm studying the properties of waves through different mediums, and got hung up on this. Is a square wave always a sum of harmonics or can we produce a square wave by quickly changing voltage? Is ...
3k views

### Basic questions about voltage drop in DC circuit

I understand all the concepts of what voltage is using all the analogies but some things related to the drop of voltage across a circuit confuses me. If I had a short circuit and attached a ...
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### What is voltage: strict but intuitive definition from accumulator's perspective

I know, that voltage is analogous to pressure for charge, but analogies lie. I don't see charge pressing anything and I don't understand definition of $U=A/q$ (voltage = work/charge), cause I can't ...
596 views

### Why doesn't a neon sign seem that hot?

I heard that neon signs contain plasma, why aren't they hot? is it because the electrons and ions do not hit the lamp's wall? Is it because it is non thermal plasma and electrons and ions are not in ...
24k views

### Why does electricity flowing through a copper coil generate a magnetic field?

Can some one please explain to me why electricity flowing though a copper coil generates a magnetic field or where I could possibly find that information? Are there other materials that produce a ...
1k views

### What does a positive gradient on a graph of V plotted against I mean in terms of EMF and internal resistance?

According to the equation $V = E-Ir$, the gradient of a graph of $V$ against $I$ should be $-r$ (internal resistance) and the Y intercept should be the EMF. Am I right? In an experiment I used a ...
8k views

### Is the same amount of electricity used for ceiling and table fans on different speeds?

We use ceiling and table fans in home which are can be set to low or high speeds using regulators. I want to ask that does it uses or consumes same amount of electricity at different speeds? Here, ...
60k views

### Why do birds, sitting on electric wires, not get shocked?

If we would touch electric wires, we would get a shock, even if we are not touching ground (so that no connection is complete form wire to ground through us). I always see that birds sit on electric ...
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### why sometimes touching old flickering tube lights starts them properly

In my old house there are two old tube lights. Some times they don't start properly, (specially at evening time, may be it is because of low voltage), they starts flickering i.e. on and off ...
543 views

### Compute closed line integral of electric field in circuit

I have a circuit where resistor is parallel to capacitor, which is charged with voltage U. How to compute line integral around closed loop to get the result of Kirchhof second law - ...
129 views

### Why are photons released from high-voltage electricity through a near vacuum?

I read an answer to what is inside a typical vacuum, and it suggested neutrinos from Space, and vapor from the container. So, maybe they add to this effect... But why are photons released from ...
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### whether electricity that comes in our home comes directly after generated or first stored and then distributed

Please give answer that, whether electricity in our home comes directly after it is generated e.g. at a dam or nuclear plant or first it is stored somewhere and then distributed as it is needed.
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### Derivation of Ohm's Law

Is it possible to derive Ohm's law (perhaps in some appropriate limit) from Maxwell's Equations?
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### The Ultimate Hand Dryer

I have come across many hand dryers that attempt to dry your hands really fast after you wash them. Here are two of them: XLERATOR http://www.exceldryer.com/ Dyson Airblade ...
15k views

### Can Gases conduct Electricity?

Liquid electrolytes ionize and hence a current can pass through them. So if a gas can ionize, can it conduct electricity too? If so, what are a few such gases?
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### Excess charge on an insulator and conductor

So I was recently wondering what happens to the excess charge when it is placed on an insulator or conductor e.g. rubbing two objects together. I know in the conductor the electrons are free to move ...
2k views

### How do electrons repel?

I understand the basics, protons have a positive charge, neutrons have no charge, and the electron has a negative charge. But looking at the lines of force from a proton, they flow outward and push ...
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### Store up cheap electricity to use later?

My utility company charges me more for electricity in the summer. Is there any way I could "save up" non-summer electricity (eg, a giant battery?) and then use it during the summer, saving myself ...
202 views

### Is an electric lamp a transducer? [closed]

Silly thought. A transducer, by definition, is a device that converts variations in one form of energy to another. An electric lamp converts electricity into visible light - the brightness may vary ...
1k views

### What's the difference between electron movement and charge movement in electricity? [duplicate]

Possible Duplicate: how does electricity propagate in a conductor? I have read that in an electrical wire electrons movement is very slow while the energy or charge is very fast. What's the ...
789 views

### Capacitance and Light Bulb And Dielectric Slab [closed]

An electric lamp having coil of negligible inductance connected in series with a capacitor and an AC source is glowing with certain brightness. How does the brightness of the lamp change on reducing ...
71k views

### Why do grapes in a microwave oven produce plasma?

Some of you may know this experience (Grape + Microwave oven = Plasma video link): take a grape that you almost split in two parts, letting just a tiny piece of skin making a link between each ...
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### Electrical Resistance and chemistry

Can some one describe or explain what happens when too much current is passed through lets say a copper wire, I am looking for an explanation to do with physics and chemistry. For instance we have ...
140 views

### Electric generators?

When a magnet passes through a copper coil and electricity is induced into the coil, is there a magnetic resistance on the magnet as it passes through the coil?
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### Loopy lightning

What causes lightning to follow the path it does ? picture from BBC news: http://news.bbcimg.co.uk/media/images/62891000/jpg/_62891901_untitled-1copy.jpg main page: ...
34k views

### What causes an electric shock - Current or Voltage?

Though voltage and current are two interdependent physical quantity, I would like to know what gives more "shock" to a person - Voltage or Current? In simple words, will it cause more "electric - ...
886 views

### Relativistic drift velocity of electrons in a superconductor?

Is there a formula for the effective speed of electron currents inside superconductors? The formula for normal conductors is: $$V = \frac{I}{nAq}$$ I wonder if there are any changes to this ...
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### Why is the anode (+) in a device that consumes power & (-) in one that provides power?

I was trying to figure out the flow of electrons in a battery connected to a circuit. Conventionally, current is from the (+) terminal to the (-) terminal of the battery. Realistically it flows the ...
9k views

### Average power dissipated by a resistor on AC current

So let's say we have an AC current of 120 V at 60 Hz. Then i's waveform would be $$f(t) = 120 \sqrt{2} \cos(2 \pi 60 t)$$ Or rather the amplitude times $\sqrt{2}$ times \$\cos(2 \pi ...
472 views

### Sum total distance of electrons on a spherical surface

What is the sum total distance between every possible pair of point charges when there are n point charges on a spherical surface? All point charges can only and are located on the infinitesimal ...
5k views

### Where does the electricity, generated by a solar panel, go if you don't use the electricity?

I'm sorry if this question is too trivial for this Q&A forum. I am a layman when it comes to physics (though I did cover the high-school physics courses). I was wondering what happens to the ...
980 views

### Can a battery charger be too powerful for a rechargeable battery?

I got the impression that a regular iPhone charger can charge the iPhone and the iPhone won't become too hot while charging, and the charging time is standard, but if using the 10W iPad charger to ...
157 views

### Battery fully loaded, pull out the chord?

I recently bought a new phone (Samsung Galaxy 3) and when the battery is fully loaded, it says like "Battery fully loaded, pull out the chord". Is this a typo from Samsung, or would there ...
225 views

### Is it possible to generate an instrument which can generate wireless electricity?

Is it possible to build an instrument which can generate wireless electricity? I ask this since at present the electricity was passes through wires and i thought about wireless electricity I am ...
184 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 ...
1k views

### Why porcelain Insulators are brown in colour? [closed]

The porcelain insulators are brown in colour. Why?
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### A problem of approximation [duplicate]

Possible Duplicate: Why are continuum fluid mechanics accurate when constituents are discrete objects of finite size? When we apply differentiation on charge being conducted with respect to ...
3k views

### How to charge an object with electricity

I know this is a rather basic question, but how do you charge an object? Not a battery, an object. I'm guessing it involves static electricity, but I'm not sure. Some resources I've been reading talk ...
98 views

### Is Joule heating only between charged particles?

The Wikipedia page for Joule heating explains "It is now known that Joule heating is caused by interactions between the moving particles that form the current (usually, but not always, electrons) and ...
2k views

### When I connect two charged capacitors side by side, what will be the voltage across them?

Say, I have two charged capacitors, one 3mF and one 2mF. The voltage across them are 20V and 30V respectively. Now if I connect the two capacitors side by side as shown below, what will be the voltage ...
493 views

### Non-conservative Electric Field

I was watching this video from Walter Lewin and while watching these two videos, I noticed there is a "contradiction" in what he is doing. All links direct you exactly to where he begins, so you don't ...
145 views

### How to measure electrical resistance?

Is it possible to theoretically measure the resistance of passing of electrical current through liquid electrolyte (distilled water + NaOH) ?