Questions tagged [electricity]

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

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10 views

Electrical impulse through a mic

For a typical mic a singer uses to sing on the stage, how much electrical current is generated when the sound gets converted into electrical impulses? Can I get an electric shock from the energy ...
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39 views

Can temperature difference in a conductor induce charge in it?

Assume a metallic rod which is heated on its right end to maintain a constant temperature gradient in the rod. Now if we take any crossection in the rod,the right side part of the cross section has ...
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2answers
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How do elecrons move?

Do elecrons move from low to high potential or they move due to attraction by positive charge? Or is it something else, what actually happens in flow of electricity.....the concept is just so ...
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Determining the z-component of the electric field at a point near a plate [on hold]

I'm struggling with all three parts a,b,c. Any help would be great, thanks. Regards Roy Browning
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1answer
70 views

Why connect plug wires in a certain way when polarity changes in AC anyway? [duplicate]

In AC systems the two wires of a circuit alternate polarity many times per second. So positive and negative switch, half of the time a wire is positive the other it is negative. So why is it ...
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Doesn't electrical energy gets lost due to slackening of local electrical wires hinged between street electric poles?

I am talking about the wires which get somewhat loose or somewhat like parabolic shaped due to earth's gravity. What I think is due to slackness of wires there is a net increment in resistance which ...
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Stability of a dipole magnet undergoing eddy current braking in a cylindrical tube

Consider a cylindrical dipole magnet with strength $B$ undergoing eddy current braking in a conductive cylindrical tube with the axis of the magnet aligned with the axis of the tube. The magnet ...
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3answers
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Found some errors in some equations of electric power. What is the actual problem?

I think the following two equations are incorrect when $I, R$ refers to current and resistance respectively and $V$ refers to potential in the difference of potential of the two sides of the resistor ...
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Static Attachment [closed]

How could I get stretch wrap to stick to paper or toilet paper type material? I have a stretch wrap machine that shrink wraps large rolls of paper, and the current method of attaching the stretch wrap ...
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MOSFET I - Vg curve [closed]

Below graph shows the I - Vg curve in the subthreshold region, Quadritica region, and linear region for 5 different transistors. I was asked to determine which I - Vg curve in the below graph is ...
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MOSFET Band Diagram from surface to substrate [closed]

The question below asks to identify the band diagram of MOSFET at different Vg. This band diagram is drawn from oxide-silicon surface to silicon substrate. my understanding is that the band diagram ...
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Do yall know how to modify the circuit shown in the figure below so that it could be used to control central heating system? [closed]

do you know how to modify this circuit so that it can be used to control the central heating system
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1answer
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Why are the times at which max rate occurs different for the energy of a capacitor and the battery

When charging a capacitor the rate at which the battery provides energy is maximum at $t=0$ but the time at which the rate of increase in the energy of a capacitor is maximum is $t=CR\ln(2)$ (where $C$...
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1answer
57 views

What causes changes in frequency in the Nation Grid electricity supply? [duplicate]

Following the power cuts in Britain this week, we were told that lack of power being generated led to a drop in the AC frequency as shown in this graph: I understand why a stable frequency is ...
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1answer
36 views

Which is induced first EMF or Electric field?

I am quite amazed by the reasoning given by my teacher about induced electric field and induced EMF.Well,the case was of a closed conducting loop placed in a time varying but uniform(in space) ...
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1answer
34 views

Two explanations of how electric motor works: are they correct?

Let's consider the simplest model for a DC electric motor: For simplicity, we assume that over a short period of time, the current through the motor is constant. All the discussion below refers to ...
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Constructing an equation for the induced EMF, in terms of the radius of a circular loop [on hold]

In order to calculate for the curl of the induced electric field for a loop moving in a uniform magnetic field, and using the cylindrical coordinate system for a curl, it's my understanding that since ...
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1answer
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Calculating the accurate emf of an electric generator

Let's consider the following simple model of an electric generator: Many textbook say the following: The magnetic flux through the coil is $\Phi=BA\sin \theta$, where $\theta=\omega t+\phi$ is the ...
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1answer
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The currect density in materials of uniform resistivity

Inside an infinitely large piece of material that fills the whole $\mathbb R^3$ space with uniform resistivity $\lambda$ (which letter should I use, when $\rho$ has been used for charge density?), ...
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4answers
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Resistors are used to reduce current to prevent light bulbs from “exploding” but it's also said that “current remains same at all points in a circuit”

Resistors are used to reduce current in order to prevent light bulbs and other electrical components from “exploding”, but it is also said that “current remains the same at all points in a series ...
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Interesting electric shock question

So the other day I was moving a fan and I put my hand on the wire. I got an electric shock for about 5 seconds, whilst being thrown over the sofa. Now I touched it with bare dry hands, and I had bare ...
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2answers
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How exactly does fault current through a person return to the source

this question has been bothering me for a long time Say a person touch the live wire as shown in the picture, the current will flow through him and dissipates into the ground in "rings" as shown in ...
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4answers
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Can touching a single power line (on the street) kill you?

Statement: You need to touch two power lines at the same time to get electrocuted. I am kinda doubting this now because, in the video linked below, it looks like the person is only touching one line ...
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3answers
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Why does current remain constant in a series circuit although the rate at which they flow deceases due to the collisions they go through? [duplicate]

I am really confused and frustrated as I can't figure this out. If someone could clear my doubt, I'd be really thankful. According to my textbook current is the rate of flow of charge, it is ...
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1answer
41 views

How do electrons keep moving when bare copper wires are rolled? [closed]

How do electrons keep moving when bare copper wires are rolled? When someone strips the wires and coils the copper, does that not affect the communication between the devices, that is, the bits do ...
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1answer
60 views

How to prove that $\vec{E}$ is an intensive property?

In my homework I had a question to sort a few variables into intensive properties and extensive properties. I wrote that $\vec{E}$ (electric field) is an extensive property, thinking of a situation ...
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2answers
37 views

Conservation & Flow of Energy in Circuits

Before I ask my question, it's important that you know how I understand the underlying physics of circuits, so you could point out any misunderstandings or incomplete thoughts. A battery creates an ...
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1answer
47 views

Regarding the force acting on a small patch on the the surface of a charged sphere

In Purcell's Electricity and Magnetism, page 30 and 31, there is a section which dealt with the evaluation of the force acting on a small patch (the tiny square in the picture) on a charged sphere: ...
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What is the exact mechanism of flow of electricity?

When a steady current flows through a conductor, the electrons in it move with a certain average ‘drift speed’. One can calculate this drift speed of electrons for a typical copper wire carrying a ...
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Is equilibrium potential relative?

If you have a half cell reaction, let's say: $Zn$ electrode and ($SO_4^{2-}$ and $Zn^{2+}$) solution The solution will get more and more postive and the electrode more and more negative until $\...
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1answer
32 views

Charge in a conductor

How to measure net charge flowing through a current-carrying conductor or a wire without actually measuring the current?
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4answers
67 views

How to experimentally measure the number of electrons flowing through a current-carrying conductor without using any other physical quantity? [on hold]

How to experimentally find the number of electrons flowing past a given point during a given time interval without involving any other physical quantity?
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3answers
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Charging electroscope

In above picture. When near positive rod to the electroscope, electrons go to top of electroscope. then connect electroscope to ground. Why electrons go from ground to electroscope? in top of ...
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How can you create electricity from nano-scale heat flux?

This article "Engineers develop chip that converts wasted heat to usable energy" on the Science Daily website states the following claim: ...findings were published in the paper, A Near-Field ...
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1answer
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How to solve this boundary-value problem in electrostatics? [closed]

I was reading The Feynman Lectures on Physics, Vol. 2 and came across the following on page 7-1. There are a few problems for which Eq. (7.1) can be solved directly. For example, the problem of a ...
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Field forces in a battery

Does a battery take time to reach its maximum voltage because it will take time for the field forces to build up since the electrodes are initially uncharged?
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2answers
56 views

How does alternating current provide energy? [duplicate]

In my head, direct current makes complete sense; the electrons carry energy around the circuit to something being powered losing its potential and then return to the battery or whatnot to have their ...
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2answers
50 views

Why are there many turns in the primary coil of a step-up electricity transformer?

Since the voltage in a coil is proportional to the number of turns, the ratio of voltages is equal to the ratio of turns. So if you need a big increase in voltage, what stops you from having one turn ...
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2answers
56 views

AC voltage and current [duplicate]

I’ve recently started reading up on electricity and slightly confused about this. I live in Europe and our electricity is 230 volts 50HZ. I understand the two conductor wires being phase/live and ...
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1answer
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Effect of a current carrying wire on a point charge

Given a point charge $q$ near a wire carrying current as shown, what would be the effect of the magnetic field produced by the wire on this point charge $q$? I think the sign on $q$ is important so ...
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2answers
47 views

Minimum and Maximum values of Effective Resistance [closed]

Assume we have resistors of resistances $R_1$, $R_2$, $\ldots$ , $R_n$. Let these resistances be connected in a network. Are the following statements true? $(i)$ Effective Resistance is maximum when ...
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How much energy does it take to form a plasma channel with a laser?

The usage is for something like this https://en.wikipedia.org/wiki/Electrolaser I know that the laser is powered for an instant in which a plasma channel is formed for the electricity to flow through,...
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1answer
53 views

Can a Peltier/Seebeck cell transfer energy from a “thermally insulated” system converting (a part of) thermal energy into electrical energy?

Suppose you have a closed system, as per the schema attached below, which walls are thermally insulated. Suppose you want to reduce the temperature of the fluid inside the closed system, without ...
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1answer
45 views

Electric field in a circuit

The electric field is defined mathematically as a vector field that associates to each point in space the (electrostatic or Coulomb) force per unit of charge exerted on an infinitesimal positive test ...
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What is an electrified channel?

I've been asked to create a sketch of an electrified channel. I've never heard of this terminology before. I tried to Google it and it came up with either guitar related answers, or a few about ...
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1answer
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Modelling behaviour of a transformer

I'm looking for a physical-mathematical model to describe the behaviour or working point of a power transformer in dependency on its most critical parameters like oil temperature/heat dissipation, ...
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17 views

Capacitance of insulated conductor with charge on insulation surface

I have an insulated wire at high voltage (10s of kV) running above a conducting ground plane. In my case, I expect that corona discharge will occur briefly after the HV generator is turned on, but ...
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1answer
42 views

In a circuit, do surface charges get influenced by external electric fields? [duplicate]

Hello ,This image represents surface charges in a circuit caused by the battery's electric field, if you were to place an other electric field source of the same magnitude (but not connecting it to ...
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1answer
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Skin Effect Explanation

I do not understand some things about the Skin Effect. Its Wikipedia definition is: Skin effect is the tendency of an alternating electric current (AC) to become distributed within a conductor ...
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Is the flow of charges in inductor though electric field zero?

How electric field inside the wire of an inductor is zero (i.e. material of which loop is made — note material is assumed to be a superconductor), then how electrons flow in an inductor if electric ...