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

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13 views

How does a plasma globe work?

I am trying to simulate a plasma globe using computer. But I do not know how to model the motion of its filaments. My first guess is to construct a potential field. And the filaments are the paths ...
-2
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2answers
48 views

How does light get from one bulb to another in a sequence of light bulb?

How does light get from one bulb to another in a sequence of light? Like in the advertisements or a smaller group? Is it the same light?
0
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1answer
27 views

Electric and Water Flow Analogy

I’ve been studying electricity lately and it has been quite hard to understand the terminology, and picturing it in my mind. After struggling to understand what each property of electric currents ...
0
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0answers
26 views

Using increase in pressure from melting of ice to produce energy? [on hold]

When ice is melted in a sealed piston, it would increase the pressure within and cause the piston to rise, right? Could this be combined with piezoelectric generator to produce electricity? If so, why ...
0
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0answers
38 views

“+” and “-” sign in Maxwell Stress tensor

I have trouble in determining the "+" and "-" sign of momentum per unit time, per unit area of the following question. Why in the second part, $d\vec{a}$ is pointing in the $ -\vec{z} $ direction? I ...
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3answers
39 views

What would we observe from thompson's lamp thought experiment?

The thought experiment goes like this: Say there is some circuit which turns a lamp on/off with just a flick of a switch. Say its off; you flick it, it turns on; flick it again it turns off, ...
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1answer
28 views

Calculating kWh from time series of kW

I have a time series of kW where each sample is measured at regular intervals (10 seconds). Could anyone explain to me how could I calculate the total power consumed (kWh) over an hour? Thanks
-1
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0answers
29 views

what will happen when you attached your hand to a two 220 volt wire of their phase defference by 120 degree? [on hold]

What will happen when you attached your hand to a two 220volt wire with their phase difference by 120 degree?
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1answer
28 views

What happens to an Electron when its charge is transferred elsewhere [on hold]

I am vastly uneducated in the areas of physics and chemistry. I am aware that electrons do have a mass, and that they carry a charge. I think that when an electron gains energy it becomes excited and ...
0
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0answers
15 views

Carrier charge density [on hold]

A conductor has increasing cross sectional area. Will the carrier charge density change? And will the drift velocity change according to change in magnitude of carrier charge density or will it ...
18
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4answers
5k views

Birds sitting on electric wires: potential difference between their feet

We have seen birds sitting on uninsulated electric wires of high voltage transmission lines overhead without getting harmed, because sitting on only one wire doesn't complete any circuit. But what ...
0
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0answers
35 views

Power wasted and power delivered?

If a power source is supplying a current I and a voltage V, that travels to its destination through resistors of restance R is the power delivered at the destination = $VI - RI^2$, where $(Pi=) VI$ is ...
0
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2answers
19 views

combination of cells

There are m*n identical cells of emf E and internal resistance r connected in parallel rows. This combination of cells is connected across an external resistance R. For what arrangement of the ...
0
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0answers
15 views

Wattage of a motor need to move a load? [closed]

How can I calculate the wattage needed for a motor at 48 volts that is directly attached to a wheel with a diameter of 17" to move a 200 pound load that is above the single axle/wheel? Assuming the ...
0
votes
0answers
16 views

Sphere between two parallel plates [closed]

I'm stuck on the following physics question; I'm not sure how much, if any, of what I'm doing is right: A small sphere of mass 1.0 × 10−6 kg carries a total charge of 2.0 × 10−8 C. The sphere hangs ...
5
votes
4answers
515 views

How are electric flux calculations not double integrals?

A disk of radius 0.10 m is oriented with its normal unit vector $\hat{n}$ at 30$^{\circ}$ to a uniform electric field $\vec{E}$ of magnitude 2000 N/C. What is the electric flux through the disk? ...
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1answer
24 views

Battery Capacity vs. Battery draw

Pardon my ignorance but I just can seem to find an Answer to my question and I hope that you can help me. What is the equation for calculating how long a Lithium Battery can supply a device? For ...
2
votes
1answer
47 views

What are all the lines on a double circuit tower?

I understand what three-phase power is. But when I look at some pictures of a double-circuit-three-phase-power-line I see two or three lines close together? What is the purpose of these lines close ...
3
votes
1answer
47 views

Why does not my power stop when alternating current goes at 0 between positive and negative?

I am having some trouble understanding three-phase alternating current. I realize that most houses are not three-phase but single phase. Would that not mean that at some point when the flow of ...
1
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1answer
36 views

Circuits and Power

"The diagram below represents a simple circuit composed of 5 identical light bulbs and 2 flashlight batteries. Which bulb (or bulbs) would you expect to be the brightest? a) V only b) V and W ...
4
votes
2answers
67 views

Why does an electric motor burn up when you physically stop it?

As an electric motor spins, the energy from the electricity is 'conducted' to the rotor by the magnetic fields. However, when the motor is stopped, the energy becomes heat and burns up to motor. ...
-2
votes
1answer
37 views

Does 1 volt cancel out 1 ohm? Can current be 0? [closed]

$V=IR$ Right? $100 (\rm{V}) = 0 (\rm{A}) \times 100 (\rm{\Omega})$ Lets say something has $100 \rm V$ potential But since this object is surrounded by air and current is not flowing therefore there ...
3
votes
3answers
117 views

If the current is increased, is there more charge flowing or is it moving quicker?

Problem Current is the amount of charge that is flowing through a component per unit of time. For a given voltage, Ohm's law tells us that if we increase the resistance, then the current must ...
-3
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0answers
54 views

why is universe neutrally charged?

I've read that the universe is neutrally charged. Therefore the number of protons and electrons of the universe are equal. But why the universe is neutral? What problem is caused if we assume that the ...
0
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1answer
17 views

Current when the slide wire attains a constant velocity

In a slide wire generator, when the slide wire attains a final constant velocity, is the current in the circuit 0? It does not make sense if it is 0 as the area keeps increasing, allowing more flux ...
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0answers
18 views

Source of electrons in Crooks tube experiment (Inside the Discharge tube)

In the experiment, gases are put at low pressure inside the discharge tube. Now the issue that arises is a very simple one. ...
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3answers
63 views

How “earthing” electricity work?

I made a simple bulb-battery circuit and then I cut one of the wires and attached both ends to cemented floor, the bulb didn't glow, this means cemented floor is a ...
0
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2answers
45 views

Why does holding an electrical switch in between on and off states cause sparks?

If air is a bad conductor, then why do sparks develop when an electrical switch is held in between on and off states? Why are sparks generated when cables carrying heavy electric current are brought ...
0
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0answers
24 views

What do we mean by “ground” in an electrical circuit? [migrated]

What do we mean by ground in an electrical circuit? When we want to solve electrical circuits problems, we set a "ground" level which is mean that the potential on it equal to $0$. I wonder how the ...
2
votes
3answers
72 views

Electric impluses inside nerve cells

I'm not a biologist, nor physicist, but there is one thing I try to understand about the elecricity inside human body. I wasn't sure whether place this question here, or perhaps on biology portal, but ...
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3answers
203 views

Can magnetic flux be negative

I am studying magnetic flux linkage in an ac generator and it appears to be that magnetic flux linkage is negative half the time, how can this be?? Also with lenz's law why is emf defined as negative ...
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1answer
37 views

What is the relationship between the verbal definition and the mathematical definition of some quantities?

I know this is probably an easy question, but it's been a while since I've studied physics and I've started reading some circuit analysis textbooks. I'm finding hard to understand the relationship ...
0
votes
2answers
39 views

Finding the voltage of an inductor in a RL series circuit [closed]

Here is the solution: This assigned question is an odd one since it doesn't seem to have anything to do with phasors which is the chapter I am currently studying. I know that that the phase ...
0
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2answers
38 views

How much electricity can be produced by my thermoelectric generator?

I am using a thermoelectric cooler from a pc's heatsink to produce electricity. Its size is 30mm by 30mm. I will cool it on one side at -10 degree Celsius and the other at 24 degree Celsius. Can ...
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1answer
30 views

Circuit analysis: Two nodes as one?

Can I treat these two nodes in the center as if there were only one node connecting these four components?
0
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1answer
25 views

Which thermoelectric effect is better?

I am doing an experiment which requires the thermoelectric effect. I know about the Seebeck and the Peltier effects. Well, from what I have found till now on these topics is that they both can produce ...
0
votes
2answers
51 views

Water and electricity? Hot or Cold?

Is hot water or cold water more conductive for electricity or is it the same regardless?
2
votes
1answer
30 views

Steam and Electricity

If an electrical conduit with sufficient voltage were cut and lay naked inside a chamber of steam, would an electrical arc occur? As a secondary question, if the steam were subject to a stabilized ...
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1answer
26 views

Can electrons coincidentally flow along a circuit to cause current?

My understanding of circuits which are not supplied an e.m.f. is that the electrons randomly just flow about in random directions, and since there's so many of them, probability dictates that any ...
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0answers
24 views

Does back emf occur in transformers?

Does back emf occur in transformers and if so does it reduce the efficiency of the transformer and can it be reduced?
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0answers
18 views

How do the different types of energy apply to voltage in a circuit

I was just wondering what happens in a circuit in terms of different types of energy transformations. If you apply a voltage to a circuit then electrons start moving (very slowly). Since the electrons ...
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0answers
23 views

An EM problem of polarized sphere

Today, I'm doing an EM problem and my question is exactly the same as this site shows: http://www.physicsforums.com/showthread.php?t=133501 To reiterate my confusion, why we can't use that integral ...
0
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3answers
46 views

question on dipole moment of water molecule

I read a line today and don't get it: "Molecules with mirror symmetry like oxygen, nitrogen, carbon dioxide, and carbon tetrachloride have no permanent dipole moments." ...
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0answers
24 views

Why do the chargers produce persistent high pitch sound?

I have noticed that my Nexus Orb charger and a charger for the shaver produce some unpleasant high pitch sounds - near the fork. Why are they doing this? Does it indicate any problem with my ...
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0answers
23 views

Magnetic flux and transformers

I have two linked quesitons, 1. what is magnetic flux linkage's formal definitaiton and 2. when people say the flux flows better thru a soft iron core then the air what do they mean by flux flowing ...
0
votes
1answer
34 views

The shape of the graph of the equation: V= -rI + E

I have recently collected data (for a school experiment) in order to measure the EMF and the internal resistance of a solar cell. The data complied with the equation: $V = -rI + E$, i.e. the voltage ...
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1answer
83 views

The relation between the movement of electrons and energy

So, I've been enjoying reading a lot of helpful posts, but now, I found myself in the need of asking something. I have a hard time grasping the general concept of electricity / how the relation ...
1
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1answer
54 views

What is the capacitance of parallel plate capacitor with different electrode material?

What is the capacitance of parallel plate capacitor with different electrode material? The capacitance of parallel plate capacitor depends on dielectric material, surface area, and separation between ...
4
votes
1answer
44 views

Electric arc due to static discharge in a T-Shirt possible?

Yesterday, when I came home, I went to the bathroom (lights off) and i took off my T-Shirt (100% cotton) which I wore under a Shirt (50% cotton, 50% polyester). I believe to have seen a small but well ...
0
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0answers
34 views

What would the graph between P (power) and i (current) look like if the graph between V (potential difference) and i is parabolic?

The answer is same... That us the graph between P and I will also be a parabola.... Similar to the graph between V and I. But how? Can anyone explain through mathematical approach ? I used ...