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

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23 views

Why do nuclear bomb explosions create an array of visible electric discharges in the form of lightening in the upper atmosphere?

I've seen videos on the internet, showing nuclear bomb test explosions, and there appears to be a large amount of visible lightening discharging numerous times over the development of the mushroom ...
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7answers
38k views

Why does a glass rod when rubbed with silk cloth aquire positive charge and not negative charge?

I have read many times in the topic of induction that a glass rod when rubbed against a silk cloth acquires a positive charge. Why does it acquire positive charge only, and not negative charge? It ...
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1answer
45 views

How do the electrons know the route?

I've learnt in classroom that the requirements for electrical current to flow in a circuit are as follows: there must be a closed conducting path between negative and positive terminals there must ...
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1answer
119 views

Mean-free-time between collisions and drift-velocity

In a physics text book I need help to make sense of the part highlighted in yellow: This is out of context of course, so just to make it clearer: $\tau$ is the mean free time of the electrons in a ...
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1answer
16 views

When I put 2 electrodes into a electrical conductive solution, does the volume of the solution around the electrodes have biological effect?

Media these days give me a common sense that it is able to hurt someone if they step on a wet floor with a electric cord dipped in, several movies have this scene.However, I wonder if I set up an ...
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1answer
345 views

Impurity scattering temperature dependence

Is there any temperature dependence of relaxation time in impurity scattering of conducting electrons? It seems to me that there is none. But, some people claim that there is. So if you could ...
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2answers
2k views

The electric field of a conductive sphere containing a charge - grounded vs not grounded

Let's suppose we have a sphere but unlike theoretical ones it'll have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge $q$ ...
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0answers
16 views

Is the induced EMF dependent on the conventional or actual flow of electrons?

I have been studying Faraday's Law and Lenz's Law and the flow of current to oppose change in flux linkage. My question is whether the actual flow of electrons to the top of a material makes the EMF ...
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2answers
122 views

Current Electricity and E.M.F of a cell

The E.M.F of a cell is the work done in moving a unit positive charge in a loop or from the terminal to the same terminal. The force it experiences is a conservative force. Therefore, the work-done in ...
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2answers
45 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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1answer
385 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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2answers
28 views

How does electric energy flow in a circuit? [duplicate]

I have read that the electric energy flows from the battery into the circuit through electric field created outside the wires into the light bulb (or any other resistor). I have also read that the ...
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0answers
18 views

Resolution to a hotly debated question: Which is more dangerous to humans, amps or volts? [duplicate]

Many times I have heard many a self-reputed wise internet sage quote, " 'Tis the amps that kill.' I really don't think so, at least, I don't think that applies all the time. Shouldn't volts be just ...
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2answers
35 views

How does my car's remote keep running?

Two years ago, I got a new car. It comes with a wireless remote that provides keyless ignition and can unlock and lock doors at the press of a button. Just recently, I read somewhere (unfortunately ...
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1answer
36 views

The influence of electric potential of a planet to a spaceship

How does the electric potential of a planet influence a spaceship? If a distant planet is at very high potential compared to Earth. A spaceship is sent from Earth to land on the planet. Is the mission ...
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1answer
15 views

Electrostatic, electromagnetic, electric, field, force, e.m.f, p.d [on hold]

Can someone explain the difference between electrostatic force, electromagnetic force, electrostatic field, electric field, magnetic field, electromagnetic field, electromotive force, potential ...
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0answers
27 views

AC is more dangerous or DC? [duplicate]

If, though not possible DC also works on specified frequency or follows sine wave form then which one would be more dangerous AC or DC?
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0answers
24 views

Voltage between conductors in single phase line [on hold]

I am trying to understand capactiance between conductors in a single phase line, but I am stuck, I am following this ...
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0answers
26 views

How do I show $e_r$ and its first- and second time derivative?

What does a charge q moving in a circular orbit with a constant velocity (a "rotating charge") and a stationary observer that measures the E field look like? And how do I show $e_r$ and its first- and ...
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1answer
49 views

Why isn't the magnitude of the electric field in a circuit zero?

I've been re-reading my knowledge of circuits and how current flows as well as the surface charge distributions in the steady state, since it's been quite some time and we've just started studying ...
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1answer
23 views

Is battery the supplier of charge in an electric circuit?

In a simple electric circuit consisting of wires, battery and a bulb... Are the charges which flow in the circuit provided by the battery or are they coming from somewhere else?
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1answer
32 views

What does an increased time constant of a capacitor do?

If a capacitor is being charged to any voltage, what effect would increasing the time constant have on it and if a graph of Charge Q/Time T was plotted to give a positive decreasing gradient, how ...
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3answers
49 views

How much work do I need to convert 300ml of water from 25°C to 3°C? [closed]

A question on how to apply thermodynamics principles to figure out how much work is needed to hold 300ml water in room temperature at 3°C. So far I have: 1Cal for each degree per g of water. We have ...
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0answers
42 views

Question about DC & AC Generators

Main question: moving a alternating magnetic field past a coil can create AC, if the same pole is moved past repeatedly does this still generate the same amount as the AC version would? or is the ...
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0answers
36 views

Since when do humans know about electric charge? [migrated]

We know that the electron was discovered in 1897 by J.J. Thomson. So was the knowledge about charge, current, electricity and all those terms related to it which we study today discovered after it, or ...
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1answer
30 views

Is electric current a scalar quantity?

According to the definition of a Scalar quantity that i have read in class 9 is that ''those quantities which has only magnitude but no direction is known as a scalar quantity''.....But in class 10 i ...
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1answer
20 views

How can we know that a particular charge is positive or negative?

Suppose I am provided with a positive is charged....and someone tells me to find which type of charge is present in it? Then how can we detect that the body is positively or negatively charged? Is ...
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1answer
17 views

Why the electrons flow from higher potential to lower potential?

We know that every thing moves from a higher potential to lower potential. In fact we also studied in our textbooks that a charge travels from higher potential ie. Positive side to lower potential ie. ...
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2answers
264 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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2answers
35 views

Why doesn't current induced by changes in flux affect the flux, while current induced by a battery does?

Faraday's law states $V=-\frac{\mathrm{d}F}{\mathrm{d}t}$, where $F$ is flux. Since $V=IR$ for passive circuits, $I = V/R = -\frac{1}{R}\frac{\mathrm{d}F}{\mathrm{d}t}.$ But by the Biot-Savart law, ...
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2answers
45 views

Energy conversion (conceptual) question

Suppose I have a electronic car. It runs by electrical energy. So when wheels rotate, mechanical energy is produced. Then why can't we convert it back to electric energy and produce somewhat unlimited ...
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0answers
13 views

How does the phase of an alternating current change when flowing through a multi-layered material?

I have questions regarding the properties of the alternating electrical current in the following imaginary experiment: There is an AC (sinusoidal wave with frequency $f = 5\ \mathrm{Hz}$). I would ...
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2answers
51 views

How to calculate temperature of an incandescent bulb filament?

Suppose we have a light bulb, for which we know its power rating, like voltage of $12\mathrm V$, and power consumption of $10\mathrm W$. We also know it's a halogen bulb with a tungsten filament ...
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1answer
300 views

Question about superconductivity

A long cylinder of radius $R$ is made from two different material. Its radius $r<r_0$ $(r_0<R)$ part is a material with superconducting transition temperature $T_1$, and its $r_0<r<R$ ...
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0answers
10 views

Wave velocity (R)LC circuits.

I'm attempting to simulate some fluid like mechanics using circuits. Specifically wave propagation. I am attempting to measure the wave propagation velocity using an oscilloscope on the circuit below, ...
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0answers
38 views

Does earth conduct electricity?

if we connected a voltage source with its two terminals in the earth does it conduct electricity ? and why they use something like " ground or earth " in safety to let the residual charges go to the ...
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1answer
30 views

How to find the distribution of charge on two spheres connected by a conducting wire?

A solid metal sphere of radius $R$ has charge $+2Q$. A hollow spherical shell of radius $3R$, concentric with the first sphere, has net charge $-Q$. What would be the final distribution of the charge ...
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0answers
18 views

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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0answers
24 views

Does lightning have a thickness?

We have calculated (probably measured) the speed, temperature and voltage of lightning so does lightning have a thickness? Note: When a lightning occur it heats up the air rapidly causing the air to ...
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2answers
4k views

Can a camera flash light near high voltage wires create medium to pass electricity?

I found a story of a boy who took a picture with flash light near 40,000 voltage lines. When it flashed, current came to his camera (as a spark may be) and passed through his body making him dead. Is ...
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0answers
20 views

Are centrifugal fans subject to triboelectric effects, and if so can the increase in charge be predicted and measured?

A centrifugal blower is a device that moves gas, usually under power of an electric motor. The blower housing and impeller may be metallic, but often are made of plastic materials. My question is ...
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0answers
14 views

If we study an electric wire under Scanning Electron Microscope (SEM), what will be the effect of the current on the microstructure or image?

If we study an electric wire under SEM, what will be the effect of the current on the microstructure or on the image obtained from SEM? I will elaborate it a bit more: if we change the current in ...
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0answers
22 views

What does this mean: “Quantity of charge in one equivalent ”

I had the following question on my test today: "What quantity of electric charge is in one equivalent of electrical energy" At least it was roughly phrased like this. Even on the test the question ...
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3answers
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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2answers
65 views

Can a laser work forever if constant electricity is provided?

Can a laser work forever if constant electricity is provided? If we take a laser and provide it with constant electricity will the reactions in the semiconductor generate photons forever?
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1answer
46 views

Static Electricity - Plastic comb, hair and small pieces of paper doesn't work for me?

All I have to do is run the plastic comb through my hair and hover it over small pieces of paper, right? The comb should then be charged and attract the pieces of paper... but that doesn't seem to ...
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2answers
2k views

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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1answer
328 views

How is the current flow perpendicular to the wire?

This answer gives a great explanation of how surface charge builds up to force the current to move perpendicular to the wire: http://physics.stackexchange.com/a/102936/41086 However, it fails to ...
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2answers
2k views

Static electricity and door handles

I have a pair of shoes, which seem to isolate me from the ground. In effect I'm gathering static charge and every time i grab an aluminum door handle, that current discharges and that hurts. Ouch. I ...
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2answers
37 views

Simple Circuits [closed]

I have a small and easy dilemma, judging by how sophisticated the website is, and need a simple answer for it So $P=E/t$. And $P=I*V$. Therefore $E/t=I*V$. I just need an explanation on how this is ...