Questions tagged [electricity]

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

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6answers
227 views

Does in a filament of lamp still has a resistance when no current flows and if yes why?

Does in a filament lamp still has resistance when no current flows?
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2answers
23 views

What is the difference between horizontal units and horizontal scale at an oscilloscope?

This is a picture of the data of a given measurement by an oscilloscope. I would like to know what the difference between horizontal units and horizontal scale at an oscilloscope is. I would be so so ...
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2answers
49 views

How can sine waves represent both AC and sound waves?

How can sine waves be used to describe both alternating current and sound waves? In the case of alternating current, the zero crossing represents zero current, and the waveform below the zero ...
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1answer
22 views

My research inquiry on flux distribution in space

I am doing a research paper "relationship between angle of release of a swinging magnet over a solenoid and the peak emf induced in solenoid. a good sin function relation but is the increase in ...
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1answer
17 views

Why does a Secondary Cell have a lower internal resistance than a Primary one?

Hi I was wondering why would a secondary cell have a lower internal resistance than a primary cell. I had read somewhere it was due to the fact secondary cells used lead acid which has a lower ...
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1answer
36 views

Risk of electrocution under electric poles on a big raining day

Like the downpour creates a path between the high voltage wires and you or your car parked underneath them, would the current passes through you to the ground when you are walking close to electric ...
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1answer
39 views

Physical Meaning of Joule Integral

I have been reading literature on fuses and came across the joule integral or $i^2t$ value many times. Often, it is referred to as energy but I am confused because shouldn't energy be $E=RI^2t$? I ...
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0answers
23 views

How can I figure out how many terms to keep in a series solution to recover the analytical solution within a given % (e.g. 1%)? [closed]

For one of my homework problems we were tasked with finding the analytical solution as well as the Fourier series solution for a potential. I have found my two equations that do this. Analytical ...
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0answers
85 views

What is the magnetic field of a uniform steady volume current?

Consider a slab of a material of finite, non-zero conductivity, infinite in the $y$ and $z$ directions but sandwiched by two metal plates at $x=x_{1}$ and $x=x_{2}$, say i.e. we are essentially ...
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1answer
18 views

Charge piled up at the junction of two different materials

In this question, I am unable to understand why charge would pile up at the junction in the first place. This is current electricity, not electrostatics, and the current is same through both the ...
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2answers
57 views

Can current though a long wire increase its mass?

There are many electrons in a wire. When current flows in the wire, the electrons move in the wire with a very high velocity. Will it increase the mass of the wire due to Special Relativity?
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1answer
53 views

Can gravity be utilized to generate hydropower in a clean, repeatable fashion without rivers or lakes? [closed]

I came up with this idea today and am just wondering if it is feasible. It is much easier to communicate via images so I drew the attached image to convey it. The key concept is rolling a ball in ...
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2answers
60 views

Microscopic explanation of the Joule effect and dielectric on capacitors

I understand intuitively that the resistor heats up when electrical energy travels through it and mathematically that the capacitor stores more charge when we fill the space between the conductive ...
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1answer
25 views

When a capacitor discharges in a simple RC circuit, is it treated as an active component?

While deriving expression for the voltage across capacitor in a discharging RC circuit, I stumbled across whether I should treat the capacitor as an active or a passive component(To properly apply the ...
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1answer
14 views

What is the relation between the short-/open-circuit current and the band gap energy in solar cells?

For the VOC it is: VOC = E_g - something, where something is positive and depends on the Urbach energy. Otherwise it should be linear: https://aip.scitation.org/doi/pdf/10.1063/1.49397 For the ISC I ...
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Magnetoresistance induced by self current

Current in a metal creates a magnetic field around it. Can this induced field affect the electric resistance of the metal or is it necessarily external magnetic field?
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0answers
34 views

Can a beam of light, coherent or otherwise, conduct electricity, as does flame

Can a beam of light, coherent or otherwise, conduct electricity.
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1answer
51 views

Why don’t illuminated series connected (photo-)diodes bias each other?

When you connect, let's say, three photodiodes or solar cells, with a load, and you measure the voltage across the middle photodiode. Will the voltage change if the adjacent cells are in the dark if ...
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2answers
30 views

Understanding the big difference between input power and output power of system [closed]

Screw jack. ( Please see the above picture ) According to screw jack formula F=w×p/2πr ( without friction ) Here F= force , w= weight , p= pitch of the screw , r=length of the lever . Now i want to ...
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1answer
25 views

Magnetic force on a stationary body

A charged particle near a current-carrying wire does not experience a magnetic force when its velocity is equal to $0$. So why does a compass needle kept near a current carrying wire experience a ...
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3answers
99 views

Why the potential is not infinite?

One way to calculate potential (using infinity as our reference point) is to sum all the contributions of charges that are around. Let's say I want to calculate the potential at some point on charged ...
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2answers
34 views

How much voltage do you need to force charge into a material?

If I'm using electricity not to induce steady-state current, but instead to force as much charge as possible into a given material, given I know the relevant properties of the material, how do I ...
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1answer
47 views

Working Principle of a Transformer

From my physics textbook (Written by Halliday & Resnick),I came to prove that $$R_{\rm Primary}=\left(\frac{N_{p}}{N_s}\right)^2\times R_{\rm Secondary}$$ This formula is driven from the ...
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2answers
69 views

Seemingly contradictory situation in electrical system loss

In a power supply system, we know that we decrease the current and increase the potential difference. If we decrease the current by a factor of 10 and increase potential difference by a factor of 10, ...
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1answer
23 views

Why is the diffusion length defined for minority charge carriers only?

As far as I could infer from the solar cell literature, when talk is about the "diffusion length", only the minority carriers are concerned. Is there a diffusion length defined for majority ...
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1answer
32 views

What happens when the terminals of a resistor are connected together with a conducting wire [closed]

What does this mean "when the terminals of a resistor are connected together with a conducting wire, then its value is ignored when the equivalent resistance is calculated because there is no ...
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1answer
66 views

Why are we even interested in solar cells under bias voltage?

I couldn't find any answer on this super basic question. Some people on the internet say that you would not put a solar cell in an array under bias, others say that they bias themselves, but I don't ...
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2answers
176 views

How is excess grid power dissipated? [closed]

I know that power/electricity generated (from conventional power plants or renewables) is generally instantaneously consumed, with grid operators constantly ramping generation to equal demand. My ...
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1answer
17 views

Can the arc from a Tesla coil or plasma from a high powered plasma orb be redirected with an electromagnet?

So I was wondering if you could use electromagnets to redirect the electric arcs created by a Tesla coil or the plasma arcs from a high powered plasma ball so you can control the direction it is going....
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1answer
50 views

What causes the noise when you get an electric shock?

When we get a minor static electric shock, we often hear a noise associated with the shock. Or for example, when you swat a fly with a zapper, you can hear a noise from the electric transfer. What ...
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2answers
32 views

Why is an electric dipole neutral overall and still has energy?

We are taught that only charged particles have an electric field in their vicinity and a neutral object does not. But a dipole is neutral overall and still produces an electric field. Why?
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If a solenoid is bounded by a hollow cylinder of resistivity rho, and carries a current varying with time, is current induced in cylinder?

This is the top view of the crosssection. I want to know if a current will be induced in the cylinder?
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1answer
27 views

What exactly is voltage in this case?

My textbook states the following: Voltage is the same across each component of the parallel circuit. However I am confused on what the exact meaning of voltage is in this case, is voltage used ...
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0answers
44 views

How is the average time before collision $\tau$ and not $\frac{\tau}{2}$ in drift velocity?

wrt: https://www.youtube.com/watch?v=xfxEPjyIaZM&ab_channel=KhanAcademyIndia-English $\tau$ is Relaxation Time (time between 2 successive collisions) The video shows derivation of drift velocity ...
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1answer
84 views

Can an electric current be created within a closed loop of wire using an electric field?

I would like to know if a small electric current can be created in a closed loop of wire by using a strong electric field to move the free electrons within the closed loop of wire. To create this ...
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0answers
15 views

Understanding a charged isolator

If an isolator gets charged (e.g. by rubbing it to an other isolator), it can get charged. If it is negatively charged, I would expect the additional electrons to be in the conduction band, so that ...
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0answers
35 views

How can graphene at thermal equilibrium induce current?

This research from the University of Arkansas claims to harvest electrical energy from thermal vibrations in a sheet of graphene: The idea of harvesting energy from graphene is controversial because ...
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2answers
39 views

When excess electrons are in an insulator they don't move. Why is this?

Let's say you have an insulator that is electrically neutral(has no net charge). Let's say you are able to add additional electrons into the same insulator resulting in the insulator having a net ...
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1answer
28 views

When you introduce excess charge into an insulator the charge stays still. Why is this?

When you add charge to an insulator the electrons stay in the same place whereas in a conductor they spread apart. Why is this? What force is making the excess charge stay in one place in an insulator?...
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0answers
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More digestible alternative to Bill Beaty's website, amasci.com

I'm currently learning electrical engineering alone and I found this website, created by Bill Beaty, which answers a lot of questions I had about electricity. The issue is that it's an old website, ...
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0answers
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Household Wiring [migrated]

I have a quick query regarding household wiring .When I connected the Green wire with red wire , the Fluke multimeter read 177 V ac, green and black wire read 44 V ac . The electric supply that comes ...
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3answers
103 views

Can electricity flow both ways?

Can electrical current flow both ways at the same time in the same wire? If so, what are the drawbacks or complications of it?
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21 views

How to start an electron avalanche?

How can I create an electron avalanche? How can I compute the necessary conditions for it to happen(voltage required, ideal electrode distance, etc.)? Is there a formula for it? And after the electron ...
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2answers
23 views

How to find the direction of the magnetic field in a toroidal inductor?

I drew sort of a picture down below (although the cell is supposed to be an ac supply). I don't understand which direction the magnetic flux? This is because, the current-carrying wire has individual ...
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1answer
13 views

How can the metal sphere connected to a ground in a Van de Graaff generator becomes electrically charged?

I am currently experimenting with a homemade Van de Graaff generator. The design looks just like in the Wikipedia page here. In many designs of the VDG, I see that the bottom comb is connected to a ...
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2answers
47 views

Troubleshooting a homemade Van de Graaff generator [closed]

I am building a homemade VDG generator and it does not seem to provide any electrical charges. My construction is as follows: The top roller is PVC, it is "pierced" (I don't know the ...
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1answer
37 views

Why is the cathode filament in an x-ray tube negatively charged?

Quoted from BU-104b: Battery Building Blocks: The electrode of a battery that releases electrons during discharge is called anode; the electrode that absorbs the electrons is the cathode. Based on ...
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0answers
32 views

How to calculate Complex Magnetic Impedance from Conductivity and Complex Permiability

For a week now I've been been racking my head trying to figure out how to calculate the Complex Magnetic Impedance of a material from its properties, namely Complex Permeability, and Conductivity. But ...
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1answer
72 views

A discrepancy on Wikipedia or a misunderstanding on my part?

Recently I have been trying to understand complex magnetic impedance and when I try to formulate the equations for it based off the similar equations for electrical circuits I keep coming up with some ...
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1answer
67 views

What do we exactly mean by charge and why the elementary charge of electron is $1.602176634×10^{−19} C$? [closed]

A coulomb is 6.241 x 10^18 elementary charges. But what exactly is a coulomb? And what do we mean exactly by a charge? how was it measured?

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