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

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How power lines use high voltages with a low current?

I've read that power lines use high voltages and low currents to reduce power loss due to resistance. Looking at the formula for power - P = VI So to increase P, you increase V rather than I for ...
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1answer
18 views

Electric field of a non-conducting, non uniform sheet

I have to find an expression for the electric field everywhere (mag and direction). The sheet is lying on the yz plane with the center at the origin. The width of the sheet is equal to 2b. The charge ...
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1answer
11 views

Potential difference in a circuit of n cells = 0? How?

I was supposed to find the potential difference across any one cell in an arrangement consisting of n cells of EMF E connected in series in a closed circuit and internal resistance r. I proceeded by ...
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3answers
434 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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0answers
36 views

Determining potential in coaxial cylinders

If I have two conducting, coaxial cylinders as shown: The potential at the outer cylinder is = 0. And I apply a potential difference across both cylinders in the form $V_a - V_b = V_{ab}$, how can ...
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2answers
25 views

Electron flow: Are these two simulations contradicting each other?

These two videos explain how a diode works: https://www.youtube.com/watch?v=W6QUEq0nUH8#t=03m25s (3:25) https://www.youtube.com/watch?v=JBtEckh3L9Q#t=07m40s (7:40) In the second video, electrons ...
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1answer
44 views

Is the sea of electrons in a metal at rest when the metal is in electrostatic equilibrium?

It is said that charges inside a metal in electrostatic equilibrium are at rest, and are stationary. However, don’t the electrons have their own thermal vibrations and whatnot? Aren’t they always ...
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1answer
790 views

Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
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1answer
104 views

Microscopic fields inside a conductor

In a neutral conductor if we assume electrons as point charges, the electric field in the space between them cannot be identically zero. This microscopic field may be very weak. What if we were very ...
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2answers
99 views

How is a potential difference created between two points?

I would like to know how potential difference is created between two points?Is potential difference created by adding more electrons at one side?If that's the case how to add more electrons at one ...
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2answers
299 views

If we connect a block of p-type semiconductor only to a positive terminal, will it become positively charged?

Connect the positive terminal of a battery to a piece of p-doped semiconductor, say, silicon doped with boron. Will the terminal pull electrons out of the doped silicon, or equivalently, inject holes ...
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0answers
48 views

How can the effects of temperature be accounted for in-situ electrical resistance corrosion monitoring?

In reading the Berkeley Lab's article Rust Never Sleeps, where research is underway investigating the use of iron oxide rust as a photovoltaic, they state: Rust – iron oxide – is a poor conductor ...
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2answers
387 views

How is the current flow perpendicular to the wire?

This answer gives a great explanation of how surface charge builds up to force the current to move perpendicular to the wire: http://physics.stackexchange.com/a/102936/41086 However, it fails to ...
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1answer
354 views

If I charge a battery using a much higher current, can it explode?

If I have a 12V 4Ah lead acid battery and use a battery charger that, let's say for example, can charge 10A, 50A, or 100A. If I theoretically turned it to 100A will the battery explode? I understand ...
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0answers
111 views

Why chewing a battery increases its power? [closed]

I know almost nothing about physics. Last night my TV remote was not working. I chewed the batteries and woh! It still had power left. How does chewing a battery increases its power? I think it's a ...
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2answers
211 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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1answer
185 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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5answers
3k views

How can one derive the Ohm's Law?

I am looking for the derivation of the Ohm's Law i.e., V is directly proportional to I. Can someone help me with it?
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1answer
96 views

Potential difference between Earth's surface and 2 meters above

Assuming Earth is a charged sphere of radius $R = 6400\times10^3$ m with uniform surface charge density $\sigma = -10^{-9}$ C/m2 and with $\epsilon_0 = 8.85\times10^{-12}$ F/m I find that ...
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2answers
40 views

Do permanent magnets have an electric current surrounding them?

Permanent magnets seems to have different properties to electromagnets, such that electromagnets can be used for induction and energy transfer if a conductor is placed within their changing magnetic ...
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3answers
23k views

Why does connecting a battery's positive terminal to the negative terminal of another battery not create a short circuit?

This is a question regarding the physics behind the observation. I have guessed the answer to the question, but I may be wrong, so I want to wait for the responses before posting it. Some major ...
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2answers
251 views

Would I get a shock from a Weyl fermion?

I know this is only just a new discovery. I assume this new quasi particle is a form of what "electricians" call current. I wonder though if it is more like AC or DC when it comes to touching the ...
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0answers
12 views

If charge is carried by ions, is there a limit to the amount of charge that salt water can conduct? [duplicate]

The reason salt water is so conductive is dissolved ions (e.g. $\mathrm{Cl^-}$ and $\mathrm{Na^+}$). If I put an anode and a cathode in water, will ions eventually build up and create an opposing ...
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1answer
163 views

What happens to gas molecules after ionization?

I know that gas molecules conduct electricity after they get ionized but what will happen if we keep increasing the voltage even after ionization? Will it explode? If it will then how much energy ...
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2answers
124 views

Ohm's law holds at constant temperature - what about Joule heating?

Ohm's law states that the resistance of a conductor is constant provided its physical conditions, such as temperature, remain constant. But what I'm thinking is that as you increase the voltage across ...
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5answers
144 views

The potentiality of the electric field

Could you please explain using just words why electric the field is potentially? I know the proof using integral: $$A = \int_{12}q\vec{E}\cdot{d}\vec{r} = qQ\int_{12}\frac{\vec{r}\cdot{d}\vec{r}}{r^3} ...
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0answers
9 views

Solar Project, help needed [migrated]

I have a project where I need to install 2 ip cameras and 1 radio transmitter in a remote location that will depend on solar power. the cameras and transmitter are 12vDC and have a combined draw of ...
3
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1answer
239 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
9 views

Reasons for a voltage follower introducing voltage gain? [migrated]

Im using a 3130 op amp as a voltage follower (unity gain buffer amplifier). However it is introducing voltage gain. It is wired the following way: This is then just fed into a simple low pass RC ...
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2answers
153 views

Why Change Of Magnetic Flux Induces Current In circuit?

Why change of magnetic flux with the time through a coil induces current in it? Please tell me that what happen to charge in the coil if the magnet or electromagnet wave around this? Also, why a ...
8
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2answers
2k views

Tying knots in power cables to prevent power surge from lightning strikes

There are plenty of references to this claim on the internet that tying knots in power cables will prevent a piece of equipment e.g. television or computer from a power surge. How can this be ...
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2answers
52 views

Resistance of hollow metal sphere

A hollow metallic sphere has inner and outer radii $a$ and $b$ respectively. How to calculate its resistance between two a points $A$ (on the inner surface) and a point $B$ (on the outer surface)? ...
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2answers
30 views

How do you model the resistance across a symmetric sheet of plastic, streched (think ceran wrap) between a circular anode and cathode?

Here is the problem. You need to model the resistance across a circular sheet of polypropylene (plastic). The resistivity of polypropylene is 1E15 Ohms per meter. The expression for resistance on a ...
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0answers
43 views

Is this a good explanation of electron mobility to the layman?

I'm writing an informative paper on graphene for my writing class (layman-oriented), and was describing electron mobility in very simplified terms. Let me know if anything is mistaken, badly ...
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4answers
9k views

Why do power lines sag when they are heated up?

I was reading some information about the 2003 power blackout in the Northeastern US. Beginning early in the afternoon of August 14, 2003 big transmission lines began to fail in First Energy's ...
13
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11answers
14k views

What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)?

This is a confused part ever since I started learning electricity. What is the difference between electric potential, potential difference (PD), voltage and electromotive force (EMF)? All of them have ...
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3answers
310 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
422 views

How can one explain the Kelvin Water drop experiment without assuming the container to already possess a positive charge?

Kelvin Water Dropper experiment refers to the electrostatic generator invented by Lord Kelvin, which uses falling water to generate a voltage by electrostatic induction occurring between ...
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3answers
82 views

Does an induction cooktop consume as much energy when it's heating something as it does when it isn't? [closed]

If you plug in an electrical charger or an adapter of an electronic device such as a mobile phone or a laptop into the power socket, but you don't actually attach the device into the charger, the ...
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2answers
120 views

Why does this capillary action generator not work?

So I was doing a bit of reading. Apparently the the obstacle to generating energy from the forces driving capillary action is breaking the surface tension at the top of a capillary tube. It is just ...
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2answers
383 views

Is it possible to use induction ampermeter to measure power consumption of electric water heater and dryer?

I hope this practical question is not OT and not too trivial for this forum. I am renting an apartment in a duplex with a shared water heater and dryer. Turns out, both water heater and the dryer are ...
4
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3answers
371 views

Why does hair stand up when standing under power lines?

My initial guess would be the immense electric field around the lines, that causes hair to get charged and due to each hair having the same charge they start to repel each other. So what is exactly ...
4
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1answer
55 views

Graph of Electrical Resistivity of Air vs Air Pressure

I've search many place ( Google, forums etc ) but can't seem to find anything that explains the Relationship between: Electrical Resistivity of Air vs Air Pressure Constant Variable: ...
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1answer
157 views

Computing energy loss for a hysteresis curve

Let a hysteresis loop be as shown in the figure, with $B_0$ the applied external field due to a current $I$ in a toroid, and $B_M$ the additional field due to the ferromagnetic material. Hence we ...
0
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0answers
11 views

Do electrons transfer during static electricity by conduction to follow octet? [duplicate]

When silk and balloon are rubbed together, electrons from silk travel to balloon. Is it because balloon is trying to gain a full outer shell and become stable? Then I guess both should want to do that ...
2
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2answers
174 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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0answers
22 views

Magnetic field due to current carrying sheet

I have 2 infinite plates (x direction) with the width of A (y direction) and the distance between them is d (z direction). The current density is J on the first plate and -J on the second (the ...
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3answers
109 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
142 views

Static Electricity - Plastic comb, hair and small pieces of paper doesn't work for me?

All I have to do is run the plastic comb through my hair and hover it over small pieces of paper, right? The comb should then be charged and attract the pieces of paper... but that doesn't seem to ...
36
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2answers
3k views

Wind generators - why so few blades?

Why commercial wind generators usually have just 2-3 blades? Having more blades would allow to increase power OR decrease diameter. Decreased diameter would also reduce stress due to different wind ...