# Tagged Questions

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

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### How do you calculate the brightness of an electronic arc through a gas?

Quick question: I want to model the brightness of a xenon flash tube when a capacitor is discharged through it, but I can not find any equations related to this. It only has to be a rough model, just ...
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### What does electrically charged mean?

So I was reading my physics textbook and it said that "Suppose we have two metal spheres, one highly charged and the other electrically neutral." What does it mean by highly charged? Does that mean ...
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Why are there no electrical generators utilising the electron/s of beta decay from a radioisotope for generating a working current? For example, how much radioisotope would I need to generate 1A or ...
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### Why is the total potential difference in a circuit the sum of the individual potential differences?

I am having difficulty in applying my understanding of electrical potential to circuits. Why is the total potential difference in a circuit the sum of the individual potential differences among ...
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### Velocity of an Electron as it Passes through a Uniformly Charged Ring

I've been presented with a problem in which an electron is placed a certain distance x from the center of a positively charged ring and allowed to move freely. The ring has a known charge density λ. I ...
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### Does magnetic induction produce potential across zero resistance wire?

If magnetic field is increased at a constant rate inside a zero resistance wire loop, then, according to Faraday's law , $$\varepsilon = \frac{dΦ}{dt}$$ Thus, a potential difference is produced. ...
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### Magnetic ball Inside a rolling hollow copper sphere?

Just curious with regards to the production of electricity. What would happen if you put a magnetic ball inside a hollow copper sphere and rolled it down a hill? Where would current be generated ...
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### What causes electrical boxes to hum?

Often times you pass by an electrical box on an electrical pole and you hear a distinct hum emanating from it. What causes that tone? Does the flow of electricity itself have a sound? Or does the flow ...
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### Negative Electric Capacitance

I know electric capacitance is always positive (otherwise it doesn't make any physical sense). But the capacitance is related to the potential difference, which can be positive or negative, depends ...
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### Is wearing metal armor during lightning safe?

I recently saw in a television show that wearing a metal armor during lightning is good because metal provides the path of least resistance for electricity to flow to the ground. Now my question is,is ...
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### Why did LED lit up while soldering? [closed]

I was soldering an LED when accidentally the soldering wire touched the LED's other Pin while the soldering iron was touching the other and the LED lit up, not bright but bright enough to be seen. I ...
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### A working “mechanical” model that explains current in a wire/circuit?

In class we learned about point charges, electrostatic force, voltage, current etc. and discussed circuits along the way. Now problems arise when I try to apply the learned concepts to explain how ...
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### Electric field outside conductor with cavity

Recently I heard a lecturer claim that the electric field outside a solid conductor containing a cavity with a point charge $q$ at a point $\mathbf{r}$ is the same as the electric field due to the ...
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### What makes Human a Conductor

Conductors, are those which have free electrons... and because of this have same electric potential all over. But considering our body, which has many electrical voltage, current signals passing by in ...
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### Charging identical spheres using induction

Suppose I can induce a charge Q in a conducting sphere by the traditional induction method, then why is it that the charges would be equally shared if I put this sphere in contact with another ...
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### Tough mudder “Electroshock therapy” obstacle [closed]

The Tough mudder is an obstacle race where some obstacles test someone's mental grit. One of the obstacles is the "Electroshock therapy" where someone has to run through dangling wires that carry ...
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### Can I electrify a pin by applying current in its base? [closed]

I imagine electric circuits as loops. So I wonder, if it is possible to electrify a pin without connecting its two edges, instead only applying current at its base. But I want the current to run ...
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### heating elements and arc welding?

In a water heater stove or arc welder, the most basic electric circuit is formed when one has a source (AC or DC) and 2 wires going to and from the heating element, in the case of the heater and ...
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### Why do electric shocks send you flying?

One question which has recently been interesting me is: Why exactly do people get thrown back when they are shocked by electricity. I have done some research to find the answer to this, and i am yet ...
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### Galvanic Cells and Electric Potential

In a battery or a galvanic cell, the electric potential of the battery is due to a difference of charges between the two cells like in a capacitor? So it is the electric field due to this separation ...
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### Quasi-fermi levels in a solar cell?

I was wondering, if my fermi levels splits up due to n and p type doping into two fermi levels, one for the p type one for the n type, and now due to light radiation my fermi levels split up into 2 ...
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### Is this the reason why a circuit with no components (except wire) would discharge the battery faster?

I read that if I simply connect two ends of a battery it would discharge really quick and it would last longer if the circuit contained e.g. a light bulb. I wondered why is this happening and my ...
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### What is a n-type doped solar cell?

I always thought a solar cell consists of two areas, a n-type and a p-type doped one. So what exactly is meant by n-type doped solar cells? Does it not have a p-type doped area? And how does it work ...
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### Intuitive definition of electromagnetic field

I am curious about the following: Checking about what is an EM field in wiki it says: An electromagnetic field (also EMF or EM field) is a physical field produced by electrically charged ...
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### Number of electrons flowing in a circuit [closed]

Does the number of electrons flowing in a circuit get affected when we turn on the light? If yes or no, then why. Help please.
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### What would happen if an N doped semiconductor is connected to voltage?

I've been trying to learn electronics alone, and recently stumbled upon transistors. To my understanding, transistors are like two PN junctions back to back, but with the P region very thin. This ...
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### What makes B-field not be arbitrarily large very close to an electric conductor?

Assume an inifinitely long, straight thin electrical conductor with current I. It follows from Ampere's law that the B-field intensity is proportional to 1/r, where r is the distance from the ...
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### Does a switched on power socket consume electricity? [closed]

Lets say I have a TV and a power socket but the TV switch is off however the socket switch is switched on, so will it consume electricity?
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### Tesla coil arc in air - where is it going?

here is a picture of a Tesla coil with a discharge that seemingly terminates in the air. What completes the circuit at the end of the streamers?
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### Water flow in salt solutions contemporary exposed to an electrical and constant magnetic field

When a permanent magnet is held motionless close to a salt solution which already has been exposed to an electrical field a flow in the water will be induced and can be detected by applying some ...
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### Why can xenon gas stay ionised after the “trigger voltage” is removed?

From my understanding of a Xenon flash circuit, a storage capacitor and a trigger capacitor are charged up to about 240V (both with similar RC values, but less capacitance is needed for the trigger ...
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### RF disturbances produced by transmission power lines

I need a book or paper that contains "the effects of transmission lines on the radio frequency transmission and disturbances". Could you help me find a useful textbook? Thank you
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### What state is needed to model AC 3 phase induction motor?

Suppose I have a regular 3 phase 50hz AC squirrel cage motor of known design. If I wanted to make a model of this motor, would I need to know more than: Angle of rotor Angular velocity of rotor ...
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### What is ultimate AC frequency and phenomena related to it?

Just as in title. What is the top AC frequency physically possible to obtain? And are there (and if yes, what?) phenomena occuring only at large frequencies? I'm thinking about a metallic wire. I know ...
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### Removal of heat from a closed system using electricity

I was thinking this morning about how heat could be removed from a system in such a way that it is stored for future use. My ideas are a form of thermo-electric system that converts heat into ...
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### I need some clarification about my understanding of voltages and resistance

So I was reading through this question, and I think resolved my query about what voltage actually is. I don't understand what we really mean by voltage drop But I just want further clarification ...
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### How does differing surface resistance in a parallel plate capacitor effect the field strength?

I have been trying to find out how using different conductive materials for each parallel plate for a parallel plate capacitor will effect the field strength. Meaning if one of the parallel plates ...
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### When you smooth-en a surface at microscopic level, friction increases. Why?

When I was learning a chapter related to Static electricity, my teacher had mentioned that when you rub your comb with DRY hair specifically, static electricity is generated due to friction. Further ...
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### Why do electrical storms cause metal objects to vibrate?

I am curious about the vibration of metal objects as a sign of an impending lightening strike. This is apparently a common occurrence; so much so that a quick google search will yield many pages ...
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### Why do my fingertips spark when rubbing a blanket? [duplicate]

I was sleeping in the dark when I reached over for my blanket. It slipped out between my fingers and made a light spark. I repeated in different parts of the blanket at least ten times. I can't ...
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### Levitating capacitor

As the title already says, I would like to make a large capacitor levitate. Before you dismiss this question please hear me out: In essence, this is intended to be a way to avoid the constrains of a ...
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### The source and sink phenomenological description of charge - how realistic is it?

I've heard over and over an electron described as a source of the electric field, but that is a misleading term. Source makes one thing of a tap, with a constant flow of something coming out of it. ...
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### Why do we get electric shocks when most structures are insulators?

Suppose I was standing in the sea, and touched an electric fence; I would receive an electric shock, because both my body and the sea are conductors, and create a path for the electricity to flow. The ...
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### Energy in conductors with $\vec{E}$-field

The question is deceptively simple. Suppose I have a uniform circular wire in which I have created the a E-field by some mean. We that without the source the electric field should not be there, so if ...
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### Calculating the output current and voltage of series and parallel connected solar panels

I have two solar panels, one is rated as $I=2A$ (current) and $V=20V$ (voltage) and the other as $I=3A$ and $V=15V$. If I connect them in parallel, how to calculate the current and voltage of the ...
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### What will be effects of harnessing lightning?

In Feynman's Lectures, volume 2, chapter 9, there is a mention of earth getting charged by thunderstorm lightning. It is the thunderstorms throughout the world that are charging the earth with an ...
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### Why does not a battery kept in empty space discharge on its own? If space between the terminals is empty, what prevents the electrons to flow?

Given here is the picture of a twisted battery kept in free space (vacuum). Will the battery discharge quickly? I mean, it should discharge faster than it would if we were to connect the terminals ...
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### Electric potential of a sphere at a point on its surface

I'm struggling to figure out how to determine the infinitesimal area of the sphere given in the question. More specifically, in part (b) of the question. For part (a) it's the volume so V = ...
Inspired by this video where a $9 \mu F$ capacitor is made from aluminum foil, if I had students put this together in a classroom, one question I would have is what would it take to have this power an ...