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

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115 views

Wait… why exactly does farady's ice pail experiment prove Gauss's law?

You'll notice there are no equations in this: that's because this is a question of morale, not of math. But a humble one at that! I come to learn, not to expound. But don't let that limit the form ...
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1answer
64 views

Is a CRT / Electron gun in need to be in a closed loop?

I'm trying to understand electricity and there for electrons. And so far i believe i am grasping it. But there are a few parts i have a hard time understanding. For example in as i understand it, in ...
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18 views

My electrophorus doesn't work

I have failed in generating charge using electrophorus. The charging material was a balloon rubbed with hair until it became very full of static, as well as a small piece of Styrofoam rubbed with the ...
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1answer
31 views

Electrical network of current sources - What happens if one source is defect?

Suppose you have connected in a parallel circuit a pair of, say for the sake of concretness 5 sources of 300 mA and 0,5 V each, which are themselves connected together in series. Hence, in total one ...
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47 views

A question about induced fields

This is something that I just realized bothers me, after thinking about it too much. Faradays law tells us a changing magnetic field creates a circulating electric field. This electric field has a ...
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1answer
323 views

What proved Conventional sense wrong?

What fact proved for the first time that the conventional sense of current was wrong? And when it did happen? As a corollary of this question, why do we say that electrons have negative charge? Is it ...
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2answers
245 views

Is there a formal proof for the superposition theorem?

I was just wondering whether there is a formal prove for the superposition theorem in electric circuits? I tried searching it online but couldn't find anything sufficient. Most of the sources assume ...
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19 views

What causes a larger (longer) electrical arc when using a tesla coil

So, I really don't know much about this subject, if any at all, but I'd like to do a project on it. I've done some testing with my tesla coil and there appears to be a trend such that a larger ...
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1answer
60 views

Help me understand static electricity

This is what I understand about electricity: (The following information is paraphrased from the book CODE by Charles Petzold.) Atoms are made up of protons, electrons and neutrons. Protons and ...
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28 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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1answer
69 views

How do I set up the Biot-Savart equation for the magnetic field inside a circular loop of current

The way I have derived the magnetic field for inside the current loop of radius $R$ is very different from how I have seen it online. Generally they take the equation for the magnetic field at a point ...
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42 views

How does current flow in the circuit during negative cycle of input?

So,as far as I know the input signal just controls the current from +Vcc as per this analogy But in the first picture during the negative half cycle of the input waveform the output wave form is ...
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2answers
97 views

Why can't mutual inductance create perpetual electricity?

Consider the following image. When the battery is connected then current starts flowing through the primary cicuit and magnetic flux changes through the coil, this causes electricity to be induced ...
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1answer
83 views

What material can achieve the highest temperature before failing when being heated by electricity?

Just as a qualifier, I barely made it through physical science in college, so... Please be detailed in your answers and assume I know nothing. Let's say I wanted to make an electrical coil for the ...
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0answers
16 views

Temperatures reached in arc flashes

Good morning, I have a question regarding the arc flashes. Some papers mention that temperatures of nearly 20000 K can be reached during an arc flash. Could anyone explain how to come up with those ...
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1answer
26 views

charge density is a constant or a scalar-value function of position?

Since it is "density", I suppose that such values as charge density of a volume region $\rho_v$, charge density of a line $\rho_L$, and charge density of a surface $\rho_S$ is a constant but I ...
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1answer
161 views

How is current produced in semiconductors or metals?

I think current is the movement of electrons through the wire or semiconductor, thus when I press the switch of the light bulb the electrons go from positive part to tungsten and light is produced. ...
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3answers
60 views

Electric warning signs question

I've always wandered why do the warning signs show the voltage, not the current. I mean, it's the current that kills you.
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1answer
53 views

Electricity from effervescence, is it possible?

I've had this idea for quite some time (after having a cold and seeing Tabcin sparkling tablets), is there the possibility to generate electricity from effervescence? I envisioned something like the ...
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1answer
52 views

What is the positive charge in a capacitor made of?

A capacitor is a pair of conductors separated by an insulator. When it gets charged we have negative charges in one of the plates and positive charges in the other. Negative charges are electrons but ...
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1answer
178 views

How do electrons distribute themselves along a wire attached to one pole of a battery?

Let's assume we have an electrochemical cell, like an AA battery. We attach a long straight wire to the negative terminus of the battery, the other end of the wire extends right away from the battery ...
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3answers
296 views

If we connect a long wire to a battery, will battery produce more electrons?

I actually have three related questions: An open circuit chemical cell separates charges creating a surplus of electrons on its negative terminus and a shortage of electrons on its positive terminus. ...
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1answer
61 views

Thermometric Properties

A thermocouple thermometer with 10 ohms of resistance is calibrated with its hot junction and cold junction immersed in steam and melting ice respectively. An EMF of 5.6mv is measured. This ...
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16 views

In what way can a Solar storm hitting the Earth disrupt electronic equipment [duplicate]

I was reading this Wikipedia article on the 2012 Solar Storm event, which describes a Solar storm which nearly missed the Earth by a few weeks. It says that if it had hit the Earth, it would have ...
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1answer
111 views

Measured voltage on coil

I have a simple circuit of coil with inductance L $$u_c(t)= -L\frac{di}{dt}$$ and AC source with output voltage $u_s$ What is actually measured by the voltmeter ($u_c$, $u_s$ or $u_s - u_c$)? If ...
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4answers
4k views

If air cannot conduct electricity, how can lightning happen?

If air cannot conduct electricity, how can lightning happen?
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1answer
134 views

electron-gas theory of a metal (drude model) - intuition

I'm back to studying "Microelectronics" by Millman & Grabel (2nd ed.). The book makes some references to the electron-gas theory, and I found out to have some problems with my intuition. At each ...
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1answer
15 views

AC Resonances - Reduction In power

I am having trouble understanding the following; Because the Q value is based on the bandwidth at the 3dB points in the frequency transfer function, we need to find a way to measure these. In our ...
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3answers
105 views

Theoretical uncertainty of a circuit's total resistance when made entirely of resistors

My question in short(ish) is: Will the fractional uncertainty of a circuit made entirely of resistors with equal fractional uncertainties be the same as the fractional uncertainty of those resistors. ...
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1answer
188 views

Relation between Power, Voltage and Current when one or more of them is amplified?

Power(P) = Voltage(V) * Current(I) If voltage or current is amplified or multiplied what happens to power and current. Does this affect in increase or decrease in power and current values or does ...
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1answer
37 views

How did the author derive the distance the particle takes as $\dfrac{h}{cos\theta}$?

On Page 292 of Griffith's Introduction to Electromagnetism (3rd ed.) he mentions that the a basic for of a generator is one in which one pulls a square wire with one side of it in an uniform magnetic ...
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85 views

What is the real derivation of Ohm's law? [closed]

$I$ is proportional to $V$. But then how it is that I directly got $V=IR$? It looks impossible to handle this thing! If $I$ is proportional to $V$, then it must be $I=RV$. Why it is $V=IR$? The ...
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1answer
630 views

Relationship between electrical resistivity and density

I just read this answer on EE.SE and that triggered a doubt in me. If I were asked whether there is any relationship between the electrical resistivity and the density of a substance I'd answer ...
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0answers
56 views

Electric and Magnetic Field Created by Moving Electron

From a classical perspective, what are the electric and magnetic fields created by a single electron, initially located at the origin and moving along the $x$ axis with velocity $v \ll c$? I'm ...
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3answers
101 views

Electricity consumption in fan

Does regulation in a fan vary in Electricity consumption? i.e. I want to know exactly, is the energy consumption more when regulator is tuned to highest number or lowest number?
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73 views

How can I calculate the Teslas and resistance of an electromagnet?

I'm trying to build a small electromagnet to use in a generator. Right now, I have a coil of insulated 16 AWG copper wire wrapped around a large iron nail with a diameter of 1.5cm. The length of the ...
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3answers
159 views

(Capacitance of a battery?) Finding the charge accumulated on a rod

We all know the expression for the potential difference across a conducting rod moving through a region with a uniform magnetic field: $\epsilon = B l v$ Now my question is different. Is it ...
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1answer
22 views

What trioboelectric materials create the best charge?

With developing the maximum triboelectric charge in mind: What roller and belt material combinations can I easily/cheaply buy at the local hardware store to make a Van Der Graaf generator? I've ...
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0answers
46 views

Time domain reflectometry (TDR) used on conductive “block”, not wire

What would happen if you tried to use time domain reflectometry (TDR) on a conductive block, opposed to a wire? Using electrodes or something. If you could describe the physical behavior of the ...
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0answers
24 views

Why is there no charge in a capacitor connected to one battery pole? [duplicate]

Here is a very simple drawing of a battery pole and a capacitor plate connected by a wire (exaggerated in thickness). The question is, why is the capacitor not being charged? But as you will see ...
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26 views

Using theater lamp for heating [duplicate]

I'm asking myself a question about how to warm my house up, and the efficiency of such a thing : I live in a theater, and we got plenty of 1000W lighting fixture, mostly Tungsten incandescence ...
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2answers
45 views

End current without touching wire

Say I am sending a pulse down a five foot wire. If I want the pulse to not reach the end of the wire, but instead reflect at say the two foot mark, how could I achieve this without physically ...
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1answer
34 views

Meaning of potential in a discharging capacitor

I am dealing with this thing I cannot figure out. When a capacitor is discharging, the electric field inside it varies with time so we cannot perform the line integral to determine the potential ...
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1answer
218 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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2answers
18 views

Determine the size of a conductive medium

Are there any measurable characteristics that would allow one to discern the size of a conductive medium? Say I apply the same voltage to a two foot long wire and a four foot long wire. Is there ...
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1answer
71 views

Could I materialize electricity making my own lighting?

Where does electricity come from? It comes from very little charged particles inside every atom of materials. Electricity occurs when these little pieces move from one atom to another inside the ...
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2answers
142 views

Why is static electricity called static?

They called it "static" because "it doesn’t go anywhere". In order to create static electricity, you have to rub two different materials. When you rub them, the electrons move. So, why is it called ...
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1answer
300 views

The advantages of a dielectric in a capacitor

In a capacitor a dielectric can be placed in between the two plates. I have trouble understanding the points / advantages of a dielectric from what I have read in a text book. The points written there ...
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0answers
42 views

Ratings for my solar car using brushless dc motor

I need help to decide the ratings of motors,solar panels,battery ratings for my solar car.. I want my solar pannels to charge the battery while the car is running at speed nearly 70-80 km-ph. since I ...
6
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0answers
63 views

Weird phenomenon on aluminum laptop casing [duplicate]

A couple of days ago I observed a phenomenon which I'm not sure I understand correctly. My brother-in-law has recently bought an ASUS gaming laptop in an aluminum casing. When the power supply is ...