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

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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
44 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
211 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
46 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
196 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
1k 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
60 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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124 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
74 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
159 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 ...
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1answer
579 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
66 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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69 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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2answers
512 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
496 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
502 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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2answers
456 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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2answers
1k 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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3answers
1k 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
536 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
3k 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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0answers
338 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
1k 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
734 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
509 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
676 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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1answer
292 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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82 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
58 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
327 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
23 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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2answers
100 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
87 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
292 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 ...
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2answers
537 views

How to accurately mark with arrows an electric circuit

As I understood, we choose to mark the current with arrows going from the plus pole to the minus pole (even though we know that in reality it is the contrary). As I'm looking at electric circuits, I ...
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3answers
815 views

How is Kirchhoff's voltage law understood in the water flow analogy?

I met the Kirchhoff circuit laws in the past, but now I'm trying to associate them with a practical representation to be sure to understand them. Let's start with the Kirchhoff current law: If I say ...
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1answer
138 views

Does alternating current come from DC?

I wonder whether alternating current is produced from DC current or whether AC and DC are entirely different concepts. Is there any relationship between AC and DC?
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3answers
677 views

The Difference Between voltage and current

I know that this question has been asked many times before, and I have read over several of the threads asking this question, but they do not include the gripe I have with my problem of understanding ...
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1answer
2k views

Why are ammeters used in series and voltmeters in parallel?

As I'm reading a course on electricity, this one says that an ammeter should be branched inline and not on a bridge. Can someone explain to me physically why we branch a amperemeter inline and a ...
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0answers
59 views

About the nature of the electric current

I'm currently studying electricity on my own, and as I read in a metal electrons are moving across the metal freely (depending on the attraction of the nucleus). As we close the circuit, an ...
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1answer
56 views

Why is the voltage negative?

What I don't understand is why the the two voltage sources are subtracted when working out the emf for part a, The graph does not show the orientation of the solar panel so I thought I was to ...
2
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3answers
567 views

Calculate the flux of a point charge with Gauss's law

I know from my class that to calculate the flux of a point charge with Gauss's law, I have to make a surface that intersects with all of the flux lines resulting from the charge, and then make this ...
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1answer
68 views

Electrical charge equilibrium and the piezoelectric effect

About the piezoelectric effect: if I press a crystal the electrical charges segregate and an electrical voltage appears on the other two faces of the crystal. See this link for example: ...
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2answers
453 views

Is there a relationship between the diameter of a copper wire and the bandwidth it can carry?

I'd suspect intuitively that the bandwidth should decrease as the diameter decreases, but I don't have any reasoning to back it up. Secondly, would the actual wavelengths that it can carry, also ...
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1answer
102 views

Transmission lines…which one is high? potential or potential difference?

The electric potential at generating station is 11,000 V...why such high potential is generated there? From generating station it is transferred to local station...is there any electric potential at ...
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2answers
99 views

Calculate expected Voltage at a distant electrode

Firstly, please forgive me for misconceptions and errors as my knowledge of Physics is very basic. I have EEG data (uV vs time) traces for an array of platinum electrodes placed on the surface of ...
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0answers
174 views

Is ohm's law violated in electric transmission lines?

Electricity is generated at a very high voltage say, 11,000 V... Does that voltage refer to the potential difference across the transmission line or does it refer to the electric potential at the ...
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2answers
3k views

Why the current decreases with increase in voltage in transmission lines? But according to Ohm's law current should increase with Voltage

Is the Ohm's law violated here? And also why is electricity generated at 11,000 V in India?
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3answers
224 views

Reality of “electrical explosion”

I have often heard people who have been electrocuted refer to the "explosion" and how they were "thrown back" by the "blast". Sometimes the force of the blast is reported to throw people many metres. ...
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3answers
75 views

Is a flow of ionized water an electric current?

If $H_2O$ ions have a net electric charge and electric current is the flow of electric charge, can a stream of water ions be considered an electric current? If so, is it conceivably possible (not ...