Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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Why Does Change of Magnetic Flux Induce an emf?
Why does change in magnetic flux with time through a coil induce an emf across it? Please explain what happens to the charges in the coil when magnetic flux changes?
Also, why does a constant ...
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Does current flow back to the source through earth?
We know that if Single Line to Fault occurs, then fault current flows to the earth. I want to know whether the current will return to the source or not. For the current to flow we need a closed path.
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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 bear with me.
So lets begin ...
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Why does the current stay the same in a circuit?
I was informed that in a circuit, the current will stay the same, and this is why the lightbulbs will light up (because in order for the current to stay the same, the drift speed of the electrons need ...
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Explanation for speed of an electrical impulse
Our calculus book, Stewart, has a problem where they claim that for a metal cable (inner radius $r$) encased in insulation (outer radius $R$), the speed of an electrical impulse is given by
$$v = - k ...
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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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What is the physics behind the vibrating feeling you get when you touched an inducted metal surface?
When I was last working on the highway, I stopped to help a motorist parked under high tension power lines. I'm driving a large Ford Transit van, fairly box shaped. My van was parked 90 degrees (...
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How electrons move so fast in a electric circuit?
Whenever we switch on a bulb......it takes almost no time to glow up.....But we know that the atoms of a solid are tightly packed and there is a very little space between them.
So how the electrons ...
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Can an object falling in vacuum generate electricity by itself?
When an object falls through vacuum, gravitational potential energy is converted to kinetic energy. Is there some way to get electrical energy out of the equation by itself (i.e. somehow convert the ...
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I don't understand Ampere's circuital law
Since, magnetic field is a vector quantity, two (or more) magnetic fields (when in close proximity) should influence their fields, according to the laws of vector.
And by that logic, Ampere's ...
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What causes contact resistance?
When two components are combined in an electric circuit, there is apart from their own resistances a contact resistance at their junction. This causes a sudden voltage drop of $V_{drop}=R_{contact}I$....
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Why don't electric workers get electrocuted when only touching one wire? [duplicate]
I know that when electricians work on the poles on the streets, if they only touch one wire at a time they will be fine. However, from my understanding, the negative wire is connected to a large ...
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How does electricity 'decide' on it's pathway? [duplicate]
I'm struggling to understand the fundamental concepts of electricity, more specifically, the way in which it 'chooses' its optimal pathway.
I appreciate electricity will always choose the path of ...
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How does the current remain the same in a circuit? [duplicate]
I understand when we say current, we mean charge (protons/electrons) passing past a point per second. And the charges have energy due to the e.m.f. of the power supply.
Now tell me, if a lamp has ...
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Does an electric current flow in an open circuit?
When the positive and negative terminals of a battery is connected through a wire, an electric current flows across the circuit. Generally, electrons are the ones that flow (from negative terminal to ...
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computer vs heater coil comparison
If I have a computer and a heater coil that consume exactly the same amount of energy, which would be more efficient at heating my room? This is assuming that they both have the same fans and heat ...
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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 ...
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How can be the neutral wire at 0 volts when current flowing through it?
Voltage is potential difference, and current flows because of voltage. So if the voltage is zero, how can current flow through the neutral wire.
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Why does voltage remains same over Parallel Circuit
Why does voltage remains same over parallel circuit. If a resistor is connected in the circuit some of the charge should be transformed into heat and make a lack of charge after the resistor (in my ...
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Clarification of the concept "less resistance means less heating" in a wire
So my textbook says that the reason cables that are suppose to carry high currents, are thicker that those that are meant to carry lesser current, is that "less resistance (of the wire) means less ...
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How does the speed of electricity become the same as the speed of light?
"The field due to the battery sets up a surface charge in the wire. The surface charge is negative near the negative pole of the battery, and positive near the positive terminal, and varies more ...
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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 ...
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How does the electrical ground rod work?
I was reading this article about shock current path, but it seems to be contradicting answers that I have seen on this site regarding electric shock. I can't find the original question but it was ...
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Why is it easier to raise AC current to high voltage than DC?
In my country (and maybe all around the world I don't know) once electricity has been generated, it is then raised to 200k Volts for transportation.
I know this is to reduce the loss. Given $P=U.I$ ...
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Intuitive definition of electromagnetic field
I am curious about the following:
Checking about what is an EM field in wiki it says:
An electromagnetic field (also EMF or EM field) is a physical field
produced by electrically charged ...
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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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Which dissipates more power, a small or big resistor?
I was talking to someone about trying to dissipate the most heat from a metal crucible (essentially just a resistor $R$). He argued that you wanted the resistor to have a high resistance because $P=I^...
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How could one measure the capacity of a battery with one instantaneous meter reading?
My car battery when fully charged operated the car lights and air conditioning for a few minutes (without the engine being on) before it was not powerful enough to operate the starter motor.
The ...
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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 ...
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When the voltage is increased does the speed of electrons increase or does the electron density increase?
I am just a high school student trying to self study, please excuse me if this question sounds silly to you.
I know that current is a product of the speed of electrons and the electron density.When ...
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Fermi level alignment and electrochemical potential between two metals
I'm trying to get a more intuitive/physical grasp of the Fermi level, like I have of electric potential. I know that, for just a single piece of metal in equilibrium, you have to have the electric ...
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Why are $\mu_0$ and $\epsilon_0$, which appear in electrostatics and magnetostatics, related to the speed of light which appears in electrodynamics?
$\epsilon_0$ and $\mu_0$ appear in electrostatics and magnetostatics. When we include time varying fields we have electrodynamics and the appearance of c which turns out to be related to $\epsilon_0$ ...
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Tesla coil arc in air - where is it going?
here is a picture of a Tesla coil with a discharge that seemingly terminates in the air.
What completes the circuit at the end of the streamers?
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Why does electric field intensity $E$ can be uniquely determined by its divergence and curl? [duplicate]
My question is, the number of following equations
$$\nabla\cdot E=\frac{\rho}{\varepsilon}$$
$$\nabla\times E=-\frac{\partial B}{\partial t}$$
is 4 while the number of unknown variables $E=(E_1,E_2,...
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Why does it spark when I push a plug in the electrical socket?
When I slowly push a plug into the electrical socket I can often see sparks. Can anybody explain why? Can this be possibly harmful for the devices I plug in?
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Is there something like the Poynting vector for hydraulic circuits?
The Poynting vector is a representation of the energy flux in electromagnetics, showing the amount and direction of power flow at different points in space. In electric circuits, the energy is not ...
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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 or ...
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Physical interpretation related to a non-linear partial differential equation
I am doctoral student in pure mathematics working on a particular problem. My question is if this problem has applications to real world phenomena. I will try to explain the direct problem starting ...
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How can a conductor be grounded yet there are induced charges on it?
A classic example for the method of images is the following, quoted from Griffiths's Introduction to Electrodynamics, page 121:
Suppose a point charge $q$ is held a distance $d$ above an infinite ...
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Tying knots in power cables to prevent power surge from lightning strikes
There are plenty of references to this claim on the internet that tying knots in power cables will prevent a piece of equipment e.g. television or computer from a power surge.
How can this be ...
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Why don't we get a shock touching neutral wire?
Neutral wire has a V same as ground i.e almost 0. Also it carries some current. So if we touch the wire don't we to become a part of the circuit? Even if we are on the ground and current should flow ...
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How are electric flux calculations not double integrals?
A disk of radius 0.10 m is oriented with its normal unit vector $\hat{n}$ at 30$^{\circ}$ to a uniform electric field $\vec{E}$ of magnitude 2000 N/C. What is the electric flux through the disk?
I ...
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How does insulating footwear prevent an electric shock?
The reason I have always heard to explain the reduction of electric shock when we wear insulating footwear goes as follows:
When electricity passes from our body to the ground, an electric circuit ...
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Why is electric current dangerous to humans? [closed]
How does a strong electric current harm our body? A strong electric current will posses a great charge. But how does that charge injure us?
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How much is a Coulomb, really?
I've heard it said in my physics class that a Coulomb "is a lot of charge". And I believe it; most of the problems I've done in the class so far involve charges on the order of micro-Coulombs (or, ...
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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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Why does electricity need wires to flow?
If you drop a really heavy ball the ball's gravitational potential energy will turn into kinetic energy.
If you place the same ball in the pool, the ball will still fall. A lot of kinetic energy will ...
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Do wind turbines spin at constant speed? If so, how? [closed]
All electrical power fed into the electric grid needs to be an AC power source at 60 Hz (in the U.S.) to within a very tight tolerance.
My understanding is that steam turbines are kept rotating at a ...
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What's the point of an RMS value? [duplicate]
the RMS (root mean square) value of $f(x)$ is defined as:
$$f(x)_{rms}=\sqrt{\frac{\int^b_a (f(x))^2dx}{b-a}}$$
Why do we do this very specific thing of taking the square, the mean, and then the ...
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General integral to find resistance
My question is: is there a simple and truly general equation for the resistance between two electrical equipotential surfaces?. Obviously, if so, what is it, and if not, why? It would be very ...
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