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

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I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator?

I touched a tree that was touching an electric fence and got an electric shock. How is this possible if wood is an insulator? The tree wasn't wet, either and it was a pretty strong shock ,too.
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3answers
41 views

Can you die from a $250 \, \mathrm V$ broken cable? [on hold]

I have a laptop power cable that is broken, my dad taped it so it is safe now. I am just wondering: would it have killed me had I touched it? If you could state your qualification/job to show you ...
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7 views

How do you work out the energy requirement for a submerged pump?

I was wondering if you were to place a pump in a submerged container and then were to open a hatch allowing water to flood the previously vacant cavity how much energy would be required to discharge ...
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2answers
48 views

Whats the point in conserving electricity if the AC current produced cannot be stored?

If we cannot save the ac current produced in a battery or some device like the DC current there is no point in conserving it because current once produced should be consumed somehow!!
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1answer
69 views

What happens when a wire is conneceted to a plug point directly?

I did it in my school lab and at first nothing happened. Then I jiggled around, sparks flew out with a small explosive sound. It was really cool. The wire ends got burnt and the holes of the plug ...
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1answer
26 views

Dependence of Current on mobile charge carriers [closed]

How does the current flowing in a conductor depend on the number of mobile charge carrier per unit lenght? On their average velocity? on the charge per carried?
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2answers
32 views

Does a rotating DC motor near a TV affects the signals coming in the TV?

In my TV cable the signals were quite noisy so i cut the wire and hanged both the wire parallel to each other. Then the signals became very clear and everything was going alright. Once I was ...
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1answer
23 views

If I know the amperage and voltage of a bolt of lightning, how do I know what resistance a lightning rod should have [closed]

Let's say I have a lightning bolt with 100kV and 100kA current. What resistance should my lightning rod have in order for the bolt to quickly and safely pass through the material into the ground? I ...
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1answer
45 views

I wnt to know HOW to create TM, TE, and TEM waves; and is it being used in industry? [closed]

Transverse Magnetic (TM) and Transverse Electric (TE) modes So I'm wholly ignorant of any knowledge surrounding these modes, so bear with me here.. One component is infinitesimally small in the ...
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1answer
22 views

Does the Magnetic Flux change (at a point) If the wire which causes it was cutted into a half?

If the electric charges move through a wire Does the generated Magnetic flux at any certain point chanage if this wire was cut into a half
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3answers
104 views

Why are electrons attracted to a magnetic field?

In a cathode ray tube, the deflecting system can consist of either magnetic or electrically charged plates. I understand the fact that electrons are attracted or repelled by the electrically charged ...
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2answers
32 views

resistivity and temperature scan rate

100 amperes pass through a copper bar of $5$x$5$ mm cross-section. The resistivity of copper is $1.7 $x $10^{-8}$ ohm-metres. Its volumetric heat capacity is $3.45$ joules per kelvin per cc. ...
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1answer
16 views

spectrum of discharge of air

Where do the various colors in electrical discharge of air with a high voltage originate from? Are these transitions in ionized nitrogen gas or unionized gas? Are chemical reactions involved? I assume ...
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1answer
24 views

Formulas which describe Electric power loss accurate

What formulas describe the real power loss in conductors the best? I heard that there are different effects, like skin effect etc. I want to calculate the % the power drops per meter distance. ...
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2answers
43 views

Is that ground, wall conductive?

If i put my foot exposed to ground and put my finger to the USB power, i will be electrocuted. So the electron(s) from the USB power is passing over my hand, run to foot and go to ground ? As i might ...
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1answer
35 views

When do I use the various power-related equations? [closed]

Can someone please tell me when it is appropriate to use the equations $P=IV$, $P=I^2R$ and $P=V^2/R$?
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1answer
35 views

The Electric field & Coulomb's law [closed]

A point charge is moving in an electric field at right angles to the lines of forces .Does any force act on it ? Please explain why.
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1answer
26 views

Can two transformers used to make tesla coils?

Tesla coils seem to perform the same as a transformers: they use two coils and use magnetic field to transfer the energy. Doesn't using two transformers produce the same result? It doesn't seem to be ...
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2answers
43 views

Kirchhoff's current law with a nonlinear resistor

It is said that by Kirchhoff's current law $$ \frac{e - v_c}{R_1} = c\frac{dv}{dt} + f(v_c) + i\tag{1} $$ and from Kirchhoff's voltage law $$ v_c(t) = iR_2 + L\frac{di}{dt}\tag{2} $$ from the ...
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1answer
235 views

Why do the ends of tubelight blink for a considerable time even after the switch is off?

When I switch off the tube-lights , their ends blink for a considerable time. I thought as they were old, there might be some problem. But to my utter surprise, when a new tubelight was switched off, ...
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2answers
40 views

Power transmission loss in a large circuit

This is a followup question to this question Consider a large circuit like the german electric power transmission network. You have a lot of of people consuming power and a lot of power stations ...
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2answers
33 views

Kirchoff's loop law

Can any one provide me with mathematical proof of kirchoff's loop law? I am not able to understand from where to start.
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3answers
41 views

Power transmission in a circuit

lets say you have a battery and a resistance which form a circuit. The electrons flow through the resistance. How can you visualize the flow of energy. How do you visualize the energy field. I ...
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2answers
39 views

Current lagging voltage by more then 90 degrees

According to Wikipedia https://en.wikipedia.org/wiki/Leading_and_lagging_current An alternating current that reaches its maximum up to 90° behind the voltage producing it is said to be lagging. and ...
3
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1answer
70 views

What is fatal? Current or voltage? [duplicate]

I have been searching this answer for quite a while. I asked my physics teacher and he said it is current that causes death. A friend of mine, who is a EE student, and his answer was voltage. When i ...
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2answers
43 views

Does the conductivity of a wire in a vacuum decrease over time?

Does the conductivity of a wire in a vacuum decrease over time, say over the period of years or decades? In other words: Does current degrade a wire, making it less conductive? If so, by how much, and ...
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1answer
31 views

Out of phase AC transmission lines in parallel

I've been reading up on power transmission networks and came across this thing. http://en.wikipedia.org/wiki/Quadrature_booster Basically it balances the load between two parallel power lines by ...
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0answers
16 views

What does it mean to charge a length of wire up to potential v?

I have to study the text "On the Theory of the Electric Telegraph," By William Thomson, 1855. I am having trouble gaining a conceptual understanding of the opening: "Let c be the electro-statical ...
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2answers
457 views

Why do old transformers make sounds, but new ones don't?

What I think is that maybe insulation is gradually removed between plates, and eddy currents start passing from one plate to another and this produces sound. Am I right?
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2answers
56 views

Will Positron Cause flow of electricity?

Recently someone told me about antimatter. Antimatter is something that is completely opposite to matter. What I would like to know is let's say this universe was made of Anti-Matter. So since the ...
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1answer
60 views

Question on Shockley's equation for FETs

I'm currently studying FETs (Field Effect Transistors) in Navy school. What I know so far is that in FETs, $V_{gs}$ is reversed biased, creating a depletion zone. What this means in plain English is ...
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1answer
22 views

Potential Difference of a wire?

Imagine a circuit with only a 12 Volts battery and a wire connecting the ends of the battery. Point A and point B lies on the wire. What is then the potential difference between point A and B if the ...
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0answers
16 views

How does the Triboelectric effect work? [duplicate]

The general description for the Triboelectric effect (the main cause of static electricity in everyday life) is that when two certain materials come into contact, electrons are transferred between ...
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1answer
43 views

Getting Deep into Drift Velocity

We know for a metallic conductor Current $\frac{I}{enA} = v$ where $v$ is drift velocity , $e$ is the charge of an electron, $n$ is no of electrons per unit volume and $A$ is area of cross section. ...
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52 views

Polarization vector of dielectric electrostatics

I know two laws for Polarization vector of a dielectric material $$\vec P = N q \vec{\Delta L}$$ Where N is the number of dipoles per meter cube, $\vec{\Delta L}$ is the vector that represents the ...
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1answer
64 views

Can high voltage power lines attract physical objects?

An electrician told today in a conversation that 10-60 KV high power lines have a passive property of attracting (pulling towards them) physical objects (e.g. a human body), and that’s what makes them ...
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1answer
44 views

Electric Field of a circular arc at a point

Given that the circular arc wire with radius 'r' has a linear charge density λ. What is the Electric field at the origin? I took a small segment dy, which is 'θ' above the x-axis with charge ...
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39 views

Using a role-play to teach ohm's law

An education research project: can a role-play be used to help understand Ohm's Law? I need to have this analogy checked for scientific validity. A group of 25 primary children will participate, with ...
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3answers
76 views

How fast does an electron travel in a circuit?

How is it possible to calculate the speed of an electron in a circuit? What factors does it depend on?
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1answer
70 views

Why high voltage transmission lines?

This is a question which I seem to have tackled multiple times, solved each time after reading a dodgy internet explanation, then partially forgotten about and retackled half a year later. It is time ...
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3answers
53 views

Explaining the current flow of the positive shunt clipper (diodes)

I am currently studying clippers or parallel limiters in the Navy and I was wondering if someone could clear up a few things for me. Here is a picture that fits my description: A clipper has a ...
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1answer
101 views

Electricity from Pendulum

Can Electricity be generated from a pendulum?. Considering pendulum in its ideal condition i.e. it never stops. If Yes, How? Pendulum can be a simple, complex or any other type. What exactly I mean to ...
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21 views

Nichrome wire, resistance properties

Nichrome wire is often used as resistance wire, because it's got a high melting point (around $1400^\circ C$) and resists oxidation well. If you pass a current through a Copper wire, it's got a very ...
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30 views

Physical sides of Electromagnetic Wave Propagation as nonlinear in metal

This Wikipedia page says that the electromagnetic wave propagation in air can be done by Freshnel transform: $$U_{0}(x,y) = - \frac{j}{\lambda} \frac{e^{jkz}}{z} \int\limits_{-\infty}^{\infty} ...
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1answer
30 views

Graphs of electric quantities for cell with internal resistance [closed]

A cell of EMF $E$ and internal resistance $r$ is connected to an external resistance $R$. Draw graphs to show the variation of (a) $E$ with $R$, and (b) terminal potential difference $V$ of the cell ...
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1answer
36 views

Power dissipation in High Voltage Cables

I was doing the following physics problem in physics class: You have two dimensionally identical pieces of metal, one made from aluminium the other made from iron. It is given to us that ...
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1answer
19 views

Why the leafs of a gold-leaf electroscope close together?

I understand why the leafs of the apparatus repel, but why do they close together after we ground the apparatus? Are the two gold leafs are attracting each other? Or are they closing because of ...
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1answer
44 views

Why is electricity so successful (how to explain the variety of transducers we have discovered)

From piezoelectric crystals, to loudspeakers, microphones, hydrophones, strain gauges; electricity possesses the amazing ability to transfer energy/information to and from so many different media. I ...
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1answer
44 views

Solving kinetic energy exercise through electrical work formula instead of voltage formula?

While studying electric potential, I run into an issue on exercise 43 of Chapter 24 of Fundamentals of Physics 8th ed. Vol. 3 (Halliday et al.). The exercise states the following, paraphrased: A ...
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1answer
93 views

Distribution of current of a rotating cone

If I have a hollow cone (surface with no bottom cover ) as the one in the picture. The cone has surface charged density $\sigma$. It rotates around the symmetry axis with an angular velocity ...