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

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Wind turbine design question [closed]

I am planning to design a wind turbine that is has rotor blade radius of 0.915m and is connected to a generator. The generators specifications are, it is an ac generator with 5000 coil turnings and a ...
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3answers
215 views

Is the electric field strength along an equipotential surface constant?

I'm trying to determine whether or not the electric field strength $|\vec{\mathcal{E}}|$ is constant everywhere on an equipotential surface. I know an equipotential surface is defined as $$ S = ...
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42 views

Can current be induced in a grounded conductor?

I'm engaged in a rather lively debate with a group whose physics I believe to be a bit shaky. Basically they're claiming that if a conductive object is grounded to earth, the current cannot be ...
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3answers
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Do electric and magnetic lines of force physically exist?

As per my imagination any thing can't impose force on the other by not giving even a touch(i,e action at a distance). So I thought there must be some physical existence of lines of force. Although ...
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1answer
26 views

Voltage without charge

Can a non-moving charge still have a (nonzero) voltage level? Basically, if i(amperes, measuring current)=0, does V(voltage) have to be 0 too?
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1answer
51 views

Why does alternating current change direction? [closed]

As the title implies, I would like to learn why. I have read wikipedia pages in 3 different languages, searched the net and found nothing. Thanks in advance.
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1answer
25 views

Why are some Air Gap Sparks Orange?

While testing the ignition system on my car with a variable gap spark tester I noticed that the spark was orange. I suspect that there may be a problem with the ignition coil such that there is ...
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0answers
13 views

ionisation of gases by electrons

In canal ray experiment, how do accelearating electrons coming from cathode knock out electrons from the gaseous atoms in the discharge tube and thus ionise them ?what is happening exactly when an ...
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3answers
579 views

What is the voltage of an average carpet static shock? Can you make it lethal?

I think I heard somewhere that it was in the thousands of volts, but it had extremely, extremely low amps. Could you somehow transform the current to make it larger or something? Or does the equation ...
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2answers
50 views

Why are metals worse conductors when heated?

When metals, (such as in circuits), are heated, their ability to conduct electric current is hampered. Why is this? Does the transition towards liquid disrupt a metal's ability to conduct, or is ...
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0answers
13 views

Temperature dependence on conductivity of a metal in terms of band gap, conduction band, valence band,

I am trying to find an answer to the following question: Why did the conductivity of one of the metals decrease with increasing temperature? Explain in terms of ...
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0answers
28 views

I got an electric shock from a metal door…but no one else did?

Earlier today I got shocked 3 times by a metal door that didn't shock anyone else. The door (to a convenience store) is glass with a metal grate built in, and a metal handle and edges. I touched the ...
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4answers
303 views

How can there be a voltage when there is no current?

I'm told at school that the Electromotive Force (e.m.f) of a battery equals the potential difference between the terminals of the battery when there is no current. How is that possible? How can there ...
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2answers
556 views

Why does this capillary action generator not work?

So I was doing a bit of reading. Apparently the the obstacle to generating energy from the forces driving capillary action is breaking the surface tension at the top of a capillary tube. It is just ...
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2answers
189 views

How electrical energy is transfered trhough a wire, and what's flow of charge?

I've read these texts about misconceptions about electricity. This is my understanding: Electrons do move, mut slowly and randomly. What happens is that, in fact, they're just 'conducting' the ...
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0answers
12 views

Why isn't there short circuit in a Mylar conducting sheet?

Basically, we use probes connected to a ammeter to outline equipotential lines. I don't know why it's ammeter not voltmeter. Think it's because if there there is no potential difference, there won't ...
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3answers
88 views

How does the earth wire work? [duplicate]

Since we say when the live wire touches the metal casing of the appliance, the appliance gets live and touching it we feel a shock. Now let's think about the same situation having a earth wire. Here ...
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4answers
8k views
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4answers
439 views

Creating electricity from mains water pressure.

Could someone cleverer than me help me out? I had a crazy thought going through my head the other day and I can't lay my mind to rest until I get an answer. Q. How much energy could be produced by ...
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4answers
10k views

Relation between Power, Voltage and Current when one or more of them is amplified?

$$\text{Power}(P) = \text{Voltage}(V) \cdot \text{Current}(I)$$ If voltage or current is amplified or multiplied what happens to power and current. Does this affect in increase or decrease in power ...
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1answer
13 views

How much current travels transversely in a coil ?

Excuse the the cryptic q. I was just wondering, say in a guitar pickup or AC transformer, we have a coil of copper wire that is coiled around a magnetic core(s). Current is induced in the wire by the ...
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2answers
13k views

How to know what materials are good conductors of electricity?

I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean.
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0answers
16 views

What material used in soil based microbial fuel?

I have seen from wikipedia that there are soil based microbial fuel which need only anode and cathode while soil itself could act as proton exchange filter But what kind of other material it needed? ...
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1answer
36 views

power in an ac circuit - difference between in series and parallel

In AC-circuits, we have different kinds of power: active power $P$, reactive power $Q$ and apparent power $|S|$. Let's say we have a circuit with a resistor $R$ and an inductor $L$. My understanding ...
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2answers
71 views

How could a solar eclipse cause my light bulb to explode? [closed]

Any explanation to this? as it happened right during the phase of eclipse or is it just coincident? I had just finished my breakfast and on the way to go outside to watch the eclipse and before it ...
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1answer
31 views

How does the jumper in Christmas lights work?

This is the structure according to my textbook: I don't know what the glass insulator are for?? But there is indeed a thin layer of insulator coating on the jumper. Why I don't know, too, what that ...
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2answers
60 views

How can the fact that there is no electric field inside a hollow conductor be explained by Faraday's ice pail experiment?

Basically something very similar to these pictures These are from two separate books. The bottom picture says that all the excess charge in an object can be transferred to an already charged metal ...
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2answers
4k 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
17 views

Does electron drift model apply to current in liquids

The electrons in a metallic conductor, tend to drift at abysmally slow speeds, but still a current is able to flow through it, because the net movement is in the direction of the applied emf. How is ...
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1answer
268 views

Application of Displacement Current

I'm reasonably happy with the derivation and results of displacement current, however, I'd like to be aware of a few practical applications of this idea. So far, the only one I'm aware of is when ...
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0answers
122 views

Electric Honeycomb

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on ...
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8answers
24k views

Why is the charge naming convention wrong?

I recently came to know about the Conventional Current vs. Electron Flow issue. Doing some search I found that the reason for this is that Benjamin Franklin made a mistake when naming positive and ...
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0answers
9 views

Discharge Static Electricity from Carpet without chemicals

I've got a large amount of static electricity built up in a room. Is there any way I could discharge the static without the use of chemicals?
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1answer
212 views

Why don't we feel shock when there is lightning? [closed]

When there is lightning in the sky and I am are standing on the ground having no insulating material between me and the ground, why do I not feel an electric shock? If this looks stupid to you I am ...
2
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1answer
29 views

What are the clicking sounds when static electricity occurs?

Sometimes, when there's static electricity, soft clicking sounds can be heard. This may happen when two fabrics are rubbed or when you get a static shock. What exactly causes this sounds?
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3answers
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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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2answers
53 views

Does potential difference or electric field change with distance between parallel plates?

Say you have a set of parallel plates, one is positive and one is negative, if you change the distance between them would electric field strength change or potential difference, given the equation ...
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1answer
24 views

Proving an AC current with peak amplitude of 311V is equivalent to a DC current of 220V [closed]

If one starts with an alternating current in the form of a sin wave with a peak amplitude of 311V and then goes through the usual RMS procedure of integrating $sin^2$ from 0 to 2$\pi$ then the result ...
3
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1answer
52 views

What phenomena occur in a low voltage arc between copper and graphite electrodes, and why is the result dependent on electrode polarity?

I was playing around with a laboratory power supply, drawing arcs between electrodes of various materials. I noticed phenomena that I found interesting, and couldn't really explain myself: The ...
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3answers
78 views

How can the copper wire in an electricity generator provide an infinite number of electrons? [closed]

How can copper wire in an electricity generator produce an infinite number of electrons when the is a finite number orbiting each copper nucleus?
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1answer
25 views

The Photoelectric Effect in passive cooling?

Information on the Photoelectric Effect: https://en.wikipedia.org/wiki/Photoelectric_effect Summary: Some metals release electrons when struck by a certain frequency of photon. What does this mean ...
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2answers
32 views

How is it possible to even develop any current in an inductor?

Potential difference across an inductor (ie p.d. between current exit point and current entry point) is given as $$V= -L\frac{di}{dt} -iR,$$ where $L$ is the inductance of inductor and $R$ is its ...
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2answers
46 views

What does the movement of charge in an object mean?

When it is said that charge "moves" throughout an object, like if negative charge moves to the edge of an object and the charges become polarized, does this mean that the electrons has moved to the ...
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3answers
37 views

Why is it that when potential difference across a capacitor is equal to the supply voltage, no flow occurs?

Can someone explain to me how and why this happens? I'm really confused. I'm also confused about how the net charge between 2 plates is 0.
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1answer
37 views

Will putting a rubber cap on a steel bar prevent it from getting struck by lightning?

Let's say there's a stainless steel bar pointing to the sky from the ground. Like this there's a possibility it gets struck by lightning. Now would putting a rubber cap on top of the bar change this ...
2
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5answers
4k 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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1answer
36 views

Error in current voltage relation? [closed]

The current voltage relation of diode is given by I=(e^(1000V/t)-1)mA,where the applied voltage V is in volts and the temprature T is in degree Kelvin. If I made an error measuring +-0.01 V while ...
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2answers
66 views

How quick does a regular household bulb lights up after being switched on? [closed]

In this video the narrator mentions a study in which if a light bulb lights up quicker than 40ms it would seem as though it lit up before it was even switched on. How quick does a regular household ...
3
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4answers
3k views

Is a capacitor in an open circuit charged?

Say I have a circuit consisting of a battery, a wire, an open switch, and a capacitor. The circuit is open since the switch is open. My book says that the capacitor will only be charged when the ...
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3answers
4k views

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. ...