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

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Alternative solar panels

I was doing a bit of thinking recently, when I stumbled on an interesting idea. In a simplified sense, solar cells function by absorbing light and converting it into electrical energy. Since visible ...
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176 views

Boundary conditions of this problem

We have A point charge, a homogeneously charged insulator with total charge $Q''$ which is a ball with radius $R$, a conducting metal ball with charge $Q'$, radius $R$ and a grounded metal (no ...
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73 views

In Leyden Jars, how does the outer metal get charged?

In a Leyden jar, I have read that a charged object is brought in contact with the conductor in contact with the metal inside the jar, thus giving the inner metal a similar charge. And the metal ...
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41 views

Form factor and average value [closed]

Why Our Electricity Flowing in the Sequence of 11kv,33,66,132kv,why not Flow in 10 kv,11,12,13,14 that Sequence.
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609 views

Potentiometer at null pointer!

Consider the situation when a cell of an unknown emf is being measured using a potentiometer. We slide the jockey so as to obtain the null point. Now, is there any current in the potentiometer wire at ...
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2k views

Thermo-Emf variation with temperature

In the following experiment for seebeck effect After a certain temperature, the thermo-emf begins to fall. Why does this happen? What is happening microscopically at this level to cause such an ...
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2answers
175 views

If we connect a source of electricity in a large water body ,will it be dangerous? [duplicate]

I was wondering whether a person will be electrocuted if he is in large pool or a sea which is connected through a source of electricity . As sea water is saline it will conduct electricity so will it ...
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1answer
2k views

Why does rubbing feet against sheets create a spark?

Sometimes when I'm in bed at night, I rub my feet against the sheets and light is created. What exactly is going on? I'm familiar with static electricity, and the triboelectric effect (creating a ...
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52 views

Charging a spherical capacitance

How could one charge a spherical capacitor with a battery or any other emf source?
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2k views

How do substances with like charges repel each other?

I have read in a number of places how substances with opposite charges attract each other: The excess electrons in the one substance repels the electrons in the other substance so that they move away ...
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177 views

What exactly is ''electric energy''?

If the two fundamental types of energy are kinetic and potential energy, is electric energy simply the kinetic energy of charge carriers? Also, is the statement "A cell converts chemical potential ...
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226 views

Gas vs electric cooking

I've heard it said many times that you're more likely to burn food on an electric stove than a gas one, but I can't tell a difference. This seems to me to be a fallacy perpetuated by the natural gas ...
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68 views

Back $emf$ and power?

The formula relating current to back emf is $V-E=IR$ where $V$ is the source pd and $E$ is the back Emf. Thus it can be seen that as the back emf increases the current decreases. But what is the ...
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55 views

How is the wattage of electrical appliance specified?

What does it mean by a bulb is 60 Watt or 100 watt (I know it means it emits 60 or 100 Joules of energy per second, but at what conditions)? Which one glows brighter when connected in series?? What ...
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1answer
65 views

What is the difference between S/cm and Scm-1?

Conductivity is noted in S.cm-1 in this http://pubs.acs.org/doi/abs/10.1021/ja502765n i wanted to compare it to the conductivity values listed on wikipedia for common materials. i could not find ...
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2answers
129 views

Electricity and Dust

My question is, does an electrically charged material attract dust? Would it be possible to make a device like a vacuum cleaner based on a mechanism like this (in principle)?
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277 views

Why do the plugs in Europe and US have different voltage? [closed]

Is there a reason why plugs tend to be 110 V in America but 220 V in Europe? Is one of them better than the other?
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271 views

Why and how will the string break?

While i was searching on the identity discussed earlier that is $$1 + 2 + 3 + 4 + 5 + ... = -\frac{1}{12}$$ I found a similar identity applied to physics concept. It started by arranging long ...
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3answers
365 views

Static Electricity and Grounding Confusion

In an electroscope, you take metallic balls, and rub them with either a comb or a glass. Touching the balls with your finger is said to undo the effect of rubbing them with the comb or glass, since ...
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221 views

Why can't an excess of electrons or holes by themselves cause current flow?

I am a beginner in electrical engineering. Often times (most cases actually), the underlying physics aren't really explained to us and we are just left to assume that it works "because it works." This ...
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29 views

How might inducted current/ voltage in multiple coil layers connected in parallel behave?

This is a branch from this question. In the event that two or more layers are connected in parallel - would the energy created across each layer likely be significantly less? In the event of (say) ...
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64 views

Other units of resistance [closed]

Resistance is $\frac{V}{I}$, and we get the unit $\Omega$. Another unit is $\frac{W}{A^2}$. How do you derive that unit?
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1answer
212 views

Application of Displacement Current

I'm reasonably happy with the derivation and results of displacement current, however, I'd like to be aware of a few practical applications of this idea. So far, the only one I'm aware of is when ...
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7answers
17k views

Does electricity flow on the surface of a wire or in the interior?

I was having a conversation with my father and father-in-law, both of whom are in electric related work, and we came to a point where none of us knew how to proceed. I was under the impression that ...
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1answer
34 views

Relative perimittivity of conductor?

Why is the relative permittivity $\epsilon_r$ infinite for a conductor? Where does it come from mathematically and does it make physical sense?
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336 views

DC current in ideal conductor and skin effect?

I know that the skin depth derived for AC current goes as $$\delta \propto \sqrt{\frac{1}{\omega \sigma}}$$ where $\omega$ is the angular frequency of the field and $\sigma$ is the conductivty. Now: ...
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71 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 ...
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2answers
136 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?
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1answer
281 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 ...
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84 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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324 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
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4answers
9k views

Birds sitting on electric wires: potential difference between the legs

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 ...
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408 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 ...
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384 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 ...
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4answers
763 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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86 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 ...
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1answer
937 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 ...
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1answer
196 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 ...
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1answer
90 views

Circuits and Power [closed]

"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 ...
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2answers
3k 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. ...
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1answer
54 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 ...
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3answers
677 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 ...
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1answer
115 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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233 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. This is the animation for the experiment. Its pretty obvious that the ...
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3answers
2k 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 ...
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2answers
706 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 ...
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3answers
712 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
5k 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
59 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 ...
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2answers
113 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 ...