Questions tagged [electricity]

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

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If the rotational speed of a turbine at a power plant doubles, does its voltage, current or power double? [closed]

Somehow, I cannot find a simple answer to this question, or a simple equation or equations... All other things being equal, if a turbine at your local power plant instantaneously doubles its rpm (or, ...
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Force on a test charge inside a cell

Considering test charge inside a cell. Let the cell be in an open circuit. I know that a potential difference will develop between the two electrodes of the cell. If I take a test charge and place it ...
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Understanding if possibly current density can be made scalar by changing the current definition?

In the accepted answer to this question : Why does current density have a direction and not current? I understand the need for current density to be vector, but I am now curious if the definition of ...
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Brightness of Bulbs in Parallel Circuits [closed]

This is actually a question from my recent exam which I didn't understand. As far as I knew (after being explained by my teacher in class), in series circuits, the current remains the same for all the ...
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1 answer
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Why electrons and protons accepted as sub atomic particles? [closed]

Why and how electrons and protons accepted as sub atomic particles during evacuated tubes experiment. I mean they could be something bigger than atoms or could be other than atoms or could be atoms ...
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2 answers
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Voltage between 2 points of net electropositivity

Ok, so suppose we have 2 points that are overall electropositive but one is "less positive" than the other. Say point A is +50 V and point B is +20V. How will we calculate the potential ...
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1 answer
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Electric potential across a resistor

Consider a circuit with zero resistance wires, battery, and a resistor and where the direction of the current is defined by conventional current. Since there is an equal number of positive charges on ...
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4 answers
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What is electric potential really a measure of? [duplicate]

Is electric potential really a measure of the number of positive charges per volume of wire? So, a section of wire with high electric potential as a high number of positive charges, and a section of ...
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Find the external work for getting the wire from $\infty$ to the current location. (the potential in $\infty$ is $0$)

A ball of radius $R$, with charge density: $$\rho(r)=\beta r,\quad\beta > 0$$ A thin wire, with charge density: $\lambda[\frac{c}{m}]$ and length $R$, located between $x=2R$ and $x=3R$. My ...
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Why Do Van De Graaff Generators Only Shock When Grounding Someone?

When someone touchs the metal sphere of the Van De Graaff Generators, the charge on them builds up, causing the famous hair raising. However, why is it when a person is rapidly grounded by someone ...
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Does EMF depend on distance between electrodes in a battery?

E.m.f of a cell is defined as work done to carry a unit charge from cathode to anode in internal circuit. Should not work done increase with distance between distance between electrodes, and thus ...
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Derivation of the self inductance of a square loop

Is there anyone who has some references or knows how to derive this formula?
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A coherent description of wire-attraction without the magnetic force performing work

I am looking for a coherent explanation of wire-attraction, understanding the principle that the magnetic field cannot produce work, microscopically, since to each charge the force is perpendicular to ...
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1 answer
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Having difficulty understanding what the significance of permittivity in free space is

i.e. What does $\epsilon_{0}$ mean in real life? Like pressure = force exerted over an area, momentum = mv which is some measure of the motion of a mass, acceleration = how quickly the velocity ...
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Is today a power plant powered by electron-positron pairs annihilation a feasible solution to the energy crisis? [closed]

I came across this article here about a very efficient method with potential industrial applications in the electric power generation, of producing a large amount of positrons (antimatter). By ...
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1 answer
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Is it correct to describe the valence electrons in an insulator as being bound to specific atoms?

For some quick background, I work as a high voltage electrician at a major metropolitan utility. In training apprentices, we use books that are often very poor in explaining fundamental electrical ...
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SHOCKED by tile floors in a condo [closed]

I live on 10th floor if an old condo in South Florida. I have been getting shocked every time i step on floor. I need a cane and a walker. My floors are tiled. How or what device is there to help me ...
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What is the angular velocity of a wheel as a function of time as it is spun up by a DC motor?

For the sake of concreteness, let us consider a brushed DC motor. I am trying to predict how much a wheel spins up when it is connected to a DC motor for a certain amount of time $t$. Let's say I ...
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Making sparks with ice

After reading an article about friction between ice particles causing lightning in thunderstorm, this idea popped into my head Would it be possible to make sparks by rubbing ice cubes?
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2 answers
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Can you use electrical appliances inside a Faraday's Cage?

I have read that if a charge was to be placed inside the cavity of a Faraday's Cage, its electric field would be canceled by the field applied by the interior surface of the cage's conducting material,...
2 votes
1 answer
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Will an object hanging in the air acculumate static charge over time?

I remember hearing of a simple experiment about an isolated conductor hanging in the air. Due to the presence of charged ions in the atmosphere, this conductor would slowly accumulate static charge ...
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Do two charged Leyden Jars repel?

Lets assume two Leyden Jars are charged. As they now have the same charge on the outside, when I bring them next to each other, do they repel? Or, is the electrostatic force just too weak in that case?...
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How exactly is the value of DC in an AC circuit, given by the RMS of the AC

How and WHY does the RMS of current gve us the equivalent DC? I've been though this answer here:-root mean square for dc but it doesn't answer my question.
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Is tap water an ohmic conductor?

Earlier today, I asked a question regarding why I was getting weird resistance readings and based on responses which I am thankful for concluded it could possibly be the electrolysis, the fact i ...
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Is it viable to generate electricity by pulling ions from water?

I'm reading 20,000 Leagues Under the Sea, and it looks like it says the Nautilus generates electricity by pulling sodium ions from the water. This doesn't seem like it would be a viable way to ...
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What exactly is electric potential? [duplicate]

My book says: When a small positive test charge is placed in the electric field due to another charge, it experiences a force. So work has to be done on the positive test charge to move it against ...
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2 answers
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Question Regarding The Movement of Charges [duplicate]

We know that two electrons repel each other since they have like charges, which means they move in opposite directions. But how can they move if they exert equal and opposite charges, aren't the ...
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Flow of Electrons in Potential divider circuit

Take the above circuit. I'm trying to understand how current flows through this potential divider circuit. I used the following simulation to help me visualize this. In the simulation the electrons ...
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Potential divider problem [closed]

What does the curved arrow represent? The answer states that L1 will be dimmer than L2. From my current knowledge, moving the contact K closer to X will somehow increase the voltage of L2 meaning it ...
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Current density under Lorentz transformation

Imagine a conductive cylinder placed along the x axis. The cylinder has zero net charge density, however, has a positive current density in the laboratory frame. When this cylinder is observer from ...
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How does electric field apply force on charges?

As far as I understand magnetic field applies force on charges or charged/ magnetic materials via the electromagnetic waves(or photons) emitted by moving electrons. And electric field also uses ...
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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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Voltmeter connected to parallel circuit

This is my current understanding. Voltage is defined to be the potential difference between 2 points, hence it only makes sense for a voltmeter to be connected in parallel. But why must this voltmeter ...
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Trajectory of a Charged Particle in a uniform magnetic field in the context of mechanically-enforced sinusoidal motion

I want to find out what would happen to the trajectory of a charged particle, say a proton moving at an angle in a uniform magnetic field if its motion were mechanically altered by a physical barrier. ...
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Why do we take electric field inside resistor constant? [closed]

Why do we take electric field inside resistor constant
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Voltmeter in parallel

I can't seem to understand the problem with connecting a voltmeter in series. All explanations say that voltmeters have extremely high resistance so connecting it in series will effectively stop the ...
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Brightness of bulbs in Parallel

When adding bulbs in parallel, the brightness is brighter than that of series. But does that mean adding bulbs in parallel will increase the brightness of the other bulbs? My intuition is as follows: ...
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Why is nylon or silk chosen to suspend pith balls in electrostatics experiments?

In an experiment to measure the force between two charged objects two pith balls are used, and they are suspended by nylon or silk threads. Why are nylon or silk chosen for the material of the threads?...
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1 answer
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Do electrons really move on the conductor?

For my understanding: Maxwell's equations combined with Poynting's theorem give us a model where electricity is energy carried along with the electromagnetic field (energy is stored in the field, not ...
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Relation between magnetic moment in current carrying loop and magnetic moment in bar magnet

We know that for a current carrying loop magnetic moment can be calculated by $$\overrightarrow{M} = I\times \overrightarrow{A}$$ Where I is current in loop and A is the area enclosed by the loop And ...
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Electrostatic attraction between charges in different media

Imagine you have two non-conducting spheres of density a (a < density of water). Therefore the spheres float on the surface of water with a portion of their bodies immersed in water. Now how do you ...
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1 answer
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Transformers in Power transmission [duplicate]

Recently I learnt that transformers are used in the national grid to increase the voltage, so we get less current. But my understanding V=IR and by increasing the voltage we get more current, so what ...
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1 answer
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What are the conditions for a glow discharge to occur vs an electric arc to occur in a glass tube?

After the invention of vacuum pumps, people experimented with running electricity in evacuated or partially evacuated glass tubes. In some sources people say this results in a glow discharge and in ...
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Inverse temporal power-law increase of DC voltage under the application of constant DC current

Is there any material in which the DC voltage follows an inverse temporal power-law increase, under the action of a constant DC current? This implies a situation in which a constant current, I, is the ...
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Why doesn't energy supply rate equal the dissipation rate for electrical energy transmissions?

I was recently reading an example which showed that the average rate of energy dissipation due to resistance of the wires that are used in the transmission of electricity from a generator is not equal ...
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What is the maximum possible averge power of the geomagnetic electric generator?

Earth's magnetic field strength varies from 25 to 65 μT on the surface. Therefore, magnetic energy is approximately $V\frac{1}{2} \frac{B^2}{\mu\mu_0} \approx 10^{\left (17,5\cdots 18,5 \right )} \...
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Discharging capacitor: Series vs Parallel

Pretty basic stuff, but to be honest I haven't found a circuit diagram showing a capacitor discharging in parallel. The only scheme I can come up with is shown here: $\color{gray}{\textbf{[ Edited ]}}$...
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Why does an increase in drift velocity decrease electron collision?

The original statement is "The drift velocity of electrons in a metallic wire will decrease, if the temperature of the wire is increased.". My understanding is, the temperature of a wire ...
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1 answer
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Energy production of solar panels in space with received light [closed]

If there were 47.1% efficient solar panels (the MJ concentrator cells created by the NREL) in space where there is no atmosphere, I want them to generate as much power as possible, so I would like to ...
1 vote
1 answer
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Why is mean free time inversely proportional to the electric field strength?

I was looking at the mean free time formula in the Drude model, and realized that it is proportional to 1/E. I am having trouble grasping this idea. I am aware that in practical cases the drift ...
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