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

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potential profile in two battery in series

Hi I would like to know the potential profile in two series battery. Simialr as that in the attached image for single battery.
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23 views

The Electric Quadrupole

I've read the following sentence: "Every electric circuit with two pairs of accessible terminals is called a quadrupole." I was wondering why does it happen that the multipole expansion gives us a ...
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1answer
42 views

Force between two finite parallel current carrying wires

Remark: This is not a homework question...It is pure out of theoretical interest. I asked this the mathematics-community a couple days ago and got no answer, so I figured I'd try here. Most standard ...
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1answer
33 views

Finding magnetic field inside rotating sphere

A sphere with radius $R$ has constant charge density $\rho$ per unit volume. This sphere rotates as a rigid body with an angular velocity of $\omega$ around an axis that goes through the center. What ...
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1answer
26 views

Electric Dipole force exerted by a charged wire on a dipole

Why is force exerted by a charged wire on a dipole given as $F = P×(dE(r))/(dr)$ where P is the dipole moment? Please explain in simple words and avoid using too much technical derivations.I am a ...
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25 views

How does one manipulate the frequency of alternating current? [on hold]

Suppose standard voltage, current, and frequency AC power is readily available for a project that requires the available standard voltage and current, but also requires an arbitrary number of cycles ...
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273 views

How do bathroom scales measure body fat percent?

My bathroom scale has 2 metal strips each for a foot and the producer claims that it can measure body fat percent. There is a warning in the manual, that if I have heart problems (I guess pacemaker), ...
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2answers
57 views

Why do i get a shock if i touch a live wire and my feets are on ground?

I understand that there is a large potential difference but i guess we humans offer a very large resistance.So,shouldn't the current be very small .Small enough not to kill us?
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How does the specific resistance / conductivity changes, when melting metals?

According to standard school models, the specific resistance (or conductivity) depends on the movability of the charges. In a metal lattice, some electrons can freely move and are only hindered by ...
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30 views

How does non-constant conductivity change surface charge on a wire?

Current density is equal to conductivity times electric field. Therefore flux through a cross section of a wire is equal to current over conductivity. Current has to be constant along a wire. This ...
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42 views

Resistor and voltage

Considering this simple circuit : The potential is supposed to be constant along each wire (because they're conductors), such that the left wire in its entirety is at the same potential as the ...
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20 views

How to determine whether a statically charged object is positively or negatively charged?

for example, I rub a ballon on carpet. What is an experiment I can do to tell which object is net positive charged and which is negative?
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How does insulating footwear prevent an electric shock?

The reason I have always heard to explain the reduction of electric shock when we wear insulating footwear goes as follows: When electricity passes from our body to the ground, an electric circuit ...
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1answer
22 views

What device is best to prevent electric motors from burning out? [closed]

Is there any equipment to prevent electric motors from burning out? I have researched about Transient voltage surge suppressor TVSS and also Surge protection device. Can this help?
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1answer
21 views

Can an electric current's magnetic field be represented by a magnet/magnets?

Is it possible to recreate the exact same magnetic field that electric currents have with a magnet and if it is, how?
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1answer
30 views

Can we generate electric current by injecting electrons into a copper panel

Suppose I take a vacuum tube and accelerate electrons in it by electric fields then collide it on a copper plate. Will the electrons then go inside it and generate an electric current by putting a ...
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1answer
35 views

Electricity should deform the conductor then why doesn't it?

In electric current both negative particles and positive particles flow but in opposite directions. So why doesn't the conductor's shape deform because its particles are moving here and there? OR is ...
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1answer
46 views

If the electric field is not a gradient, can it exist?

We know that the gradient of the electric potential function $V(x,y,z)$ is the electric field. But not all vector fields are gradients, for example $y\hat{i}-x\hat{j}$ is not a gradient. Does this ...
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2answers
27 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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0answers
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How to calculate the capacity of an electroscope out of the geometry and why is it independent on the pointer deflection?

How can one calculate the capacity of an elektroscope like the following from the geometry of the setup? How does this formula implies that the capacity does not (approximatly) depend on the ...
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2answers
80 views

Why is the voltage of a battery equal to the emf?

We know that there is an electric field inside the battery that works against the moving electrons of a circuit. But there is also the chemical force of the battery that at some point become equal. ...
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1answer
23 views

Question regarding Van De Graff generator Belt

I have made a VDG generator with a rubber band as the belt and a glass roller. It doesnt seem to work because I think the rubber band may be conductive. I was thinking of using other materials for ...
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2answers
72 views

Is it correct to use $P=\large\frac{V^2}{R}$ for AC circuits?

In one of my old notebooks, I found a problem which was basically about finding out resistance of a 100W light bulb (In my country electricity voltage is 220V). Then our teacher had used the equation ...
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1answer
50 views

Maximum power transfer proof

I have the following homework problem. Consider a power supply with fixed emf $ε$ and internal resistance $r$ causing current in a load resistance $R$. In this problem, $R$ is fixed and $r$ is a ...
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1answer
42 views

Can we create a electric field without actually using a battery or power source?

Can we create an electric field without actually using a battery or a source of electricity? Like a take 2 panels, one is positively charged and another is negatively charged and put them parallel to ...
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1answer
32 views

Electricity from electrons

If I was able to get electrons flowing through a glass tube what happens if I put wires connected to a bulb into that stream of electrons?
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39 views

Auto spinning turbine generator

This might be dumb question but I'm so curious to know if this actually works or is impossible. I was researching how you could generate electricity from magnets and copper wire and also have read how ...
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1answer
21 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 ...
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1answer
17 views

How can DC-magnetic fields be produced with the aid of currents?

How can DC-magnetic fields be produced with the aid of currents? What's a possible theoretical explanation for this, and how does one achieve this in the real world? What are the maximum fields that ...
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1answer
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Energy Loss during Sharing of Charge between two Capacitors

It is fairly easy to show that there is always a loss energy when two capacitors share their charge to attain the same common potential, but is it with the same ease that one can explain why it ...
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3answers
82 views

Why does the electric field vanish at infinity?

When $r \rightarrow \infty$, $E \rightarrow 0$ for a point charge or set of charges or a finite charge distribution. While this seems obvious, I cannot find a reason why this is true when inspecting ...
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2answers
47 views

What causes the electrical reaction between two carbon rods touching?

I recently watched this video in which carbon rods from a 6V lantern battery are removed and then touched together to create a makeshift arc reactor furnace. This produces electrified plasma which can ...
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0answers
27 views

Plotting the Graph of $1/I$ on the Y axis against R What does this represent? [duplicate]

What does the gradient, the intercepts represent, what is the equation of my line, and how do I use this information to calculate emf?
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2answers
86 views

Crazy? Generate unusable electricity

I know that sound crazy, but today I am wondering if there is a way to generate a current that is unusable by almost all electic/electronic devices? The idea would be to generate that current and ...
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2answers
25 views

Hydro-electric gravity problem - Is there a air-resistance-like force affecting water flow down a mountain making placing hydro-electric ?

Say I have a theoretical mountain with a river starting exactly at the peak. Gravity would act on the water, accelerating it down the mountain. There would also be a force limiting the water's ...
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Electromagnetic field to shield from EMP?

Could an electromagnetic field be use to protect against an EMP? As I understand, an EMP is an Electro Magnetic Pulse, so a sufficiently powerful field should be able to deflect one, right?
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48 views

Is lightning an example of energy emision from accelerated charge?

I have always heard that the inconsistency in explaining atomic models with classical mechanics was that the study of electrical charges had shown that whenever a charge is accelerated, it emits light ...
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24 views

Conductors and electric fields

I was given this problem: The maximum intensity of an electric field that can exist near the surface of a conductor in vacuum such that no field electron emission is produced is around $10^8$ V/m. ...
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2answers
29 views

Multimeter reading between wire & air

Why does a multimeter show 10-20 V(AC) when I connect one of its cables to the hot wire of a 220 V(AC) plug while the other cable is in the air? Also why does this not happen with a 5 V battery? (It ...
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22 views

where does electricity come from in piezoelectric?

I have some questions here. BaTiO3 is a material which exhibit piezoelectric effect when we give external pressure on it. It contain Ba2+, Ti4+, and O2- ion in its crystal unit. The Ti4+ ion will move ...
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1answer
22 views

Conductor held at constant potential

What does it mean for a conductor to be held at constant electric potential? So if my reference point is infinity, and I integrate inwards over the electric field to any point on the conductor, I will ...
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2answers
18 views

Finding the torque on a dipole affected by electric field

A $H_2$ molecule with charges $\pm p$ separated by $d=10^{-10}$m and masses $1.66\times 10^{-27}$kg is put into an electric field with uniform strength $E$, making an angle $\theta$ with this field. ...
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1answer
43 views

Why does my shirt make a crackling noise when it is static?

I thought that when clothing becomes "static" (used as a colloquial adjective for that state when clothing fresh out of the drier sticks to everything) it's because of a build up of electrons. That's ...
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1answer
48 views

How two electric charges know about each other? [duplicate]

Suppose we have two electric charges $q_1$ and $q_2$ a distance $r$ apart in euclidean three-space. Coulomb's force law states that there's a force $$\mathbf{F}_{12} = \dfrac{1}{4\pi\epsilon_0} ...
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1answer
54 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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1answer
26 views

Wireless energy flow through earths magnetic field

Seeing that technologies such as that developed by WItricity are based on magnetic fields, is it possible to transfer electricity that way through earths magnetic field?
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1answer
57 views

Show that the current in a cylindrical conductor is uniformly distributed across it's cross section

Using relevant equations for E and J, show that the current in a steady current I in a cylindrical conductor with uniform conductivity $\sigma$ is uniformly distributed across its cross-section. I ...
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2answers
29 views

Long life energy usage

Im doing a project on school. I want to re-use energy. I know that it will not run forever (but i hope it runs very long). So i wanted to ask if the image below is right and i could use it at school. ...
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13 views

Biological Signal Extraction Methods

EEG / MEG Back in 1929 Hans Berger recorded the first electrical potential variations in the brain from the scalp. Great advances have been made in this science since discover, with many scientists ...
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Electric field 0 everywhere inside Gaussian surface

Gauss's Law shows that the electric field everywhere inside a spherical shell of uniform charge density is $0$. Suppose we have a surface which divides space into two disjoint regions (an interior and ...