# Tagged Questions

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

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### Why does the Emf generated by a magnet going through rings of coil generate a sinusoidal curve of Emf vs time?

I am having trouble writing the reason for the part of the curve to cut the x axis at Emf = 0 and when reason for curve to form max and min peaks.
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### Conceptual Doubt Regarding Electric Circuits [closed]

There are a few questions which have always bugged me. Unfortunately, due to time constraints, I end up memorizing an example, hoping to imitate that knowledge in an exam question. Consider the ...
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### Is it possible to express Fleming's Left Hand Rule and Right Hand Rule in terms of vectors?

I recently studied Fleming's Right Hand Rule and Fleming's Right Hand Rule for electromagnetism (For locating direction of Force, Magnetic Field and Current). Using my hands to find the direction is ...
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### Why is Electric field flux through a closed surface in Gauss's law not zero?

I learned that the vector flux through any closed surface is always 0. So if you have a sphere(closed surface) and you put it in an uniform electric field, then the total flux is 0. However, the ...
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### if the voltage is the driving force of the current, how can it lead or lag?

Correct me if I'm wrong on this, but up till now I've assumed that the voltage across a resistor could be seen as both the energy lost by a current passing through it and the energy needed for a ...
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### Batteries Do Not Supply Electrons?

I've read that a battery does not supply electrons, it establishes the electric field that exerts force on the electrons in the wires. This makes total sense to me for AC, but not for DC. The way I ...
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### why is the vertical component of the phasor an imaginary number?

I was learning about the phasor representation of AC circuits, and on adding two out of phase phasors they were each resolved in to a horizontal and vertical component to facilitate the addition. What ...
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### Are AC waves actually a sin function or just appear in their alternating nature as sinusoidal waves?

I mean do we use the graph of a sin wave just as a representation of how the current varies, or are the actual instantaneous values of current really an output of a sin function of the angle the ...
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### Why are electric shocks felt asymmetrically?

I have been zapping people quite a lot recently (e.g. when shaking hands), probably due to new shoes. What I noticed is that usually I can't actually feel the shock, even though the other person quite ...
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### Why do they rub rubber with wool while glass with silk and not otherwise?

why not the other way round, and why do they choose wool and silk in particular to charge the rubber and glass rods ?
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### Movement of charges in presence of electric potential difference

This might appear to be a bad question to some but i can't figure out the answer. While reading about an electric circuit, i found this on the web: Over the course of time, one could think of ...
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### Effect of potential difference on capacitance

I've read multiple threads here discussing the relation between capacitance and potential difference and they have begun to confuse me. I have a homework question about which of the following will ...
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### Ambiguity on the notion of potential in electrical circuits?

As everybody else I have been taught elementary electrical circuits from secondary school to engineering level in analog electronics at university. Invariably, the notion of potential used to ...
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### Electronic Transport not covered by Bandstructure in Solid State Physics

From what I have read, most of the electronic transport phenomena in solids state physics seems to able to be determined with the bandstructure. Schottky Barriers, bandgaps, band discontinuities can ...
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### Why is the electric current instantaneous while the drift velocity of electrons is slow? [duplicate]

The speed of an electron is very slow while going through a conductor(like 1mm per second),but the current passes instantaneous.why?
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### Mean-free-time between collisions and drift-velocity

In a physics text book I need help to make sense of the part highlighted in yellow: This is out of context of course, so just to make it clearer: $\tau$ is the mean free time of the electrons in a ...
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### Null point (vector) between n point charges

I have derived the result for 2 positive charges, and for one positive one negative can be obtained by using the minus sign correctly. But I was unable to extend it or solve for n charges. Is my ...
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### Lightning Conductor Working

During a thunderstorm charges collect on clouds until a field which is more than the air's dielectric strength is created. Because now there is a potential difference between the ground (0 Volts) and ...
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### What could magnetic monopoles do that electrically charged particles can't?

I understand the significance to physics, but what can a magnetic monopole be used for assuming we could free them from spin ice and put them to work? What would be a magnetic version of electricity? ...
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### What is the reason for extremely high speed of electric current?

I know that electric current is the flow of electrons but electrons have a very slow drift speed (about 2mm/s). How is it that electric current reaches its destination at almost the speed of light?
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### Magnetic field of rotating charged insulating loop

A charged insulated square loop of side length $a$ is rotated about an axis perpendicular to its plane. What is the ratio of the magnetic field in its centre to the magnetic field of a rotating ...
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### Are objects generally neutral or charged?

Basically the questions relates to what is taught about electroneutrality and has 2 parts: Is the overall charge in the universe zero? Are objects the world generally neutral or slightly charged, ...
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### relationship between electrical resistance and Hagen Poiseuille's law

For the electrical resistance of a conductor, we have $$R = \rho \frac{l}{A}$$ Noting the structural similarity between the Hagen-Poiseuille law and Ohm's law, we can define a similar quantity for ...
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### Understanding the relationship between electricity and magnetism

I keep on hearing that magnetism is just another form of electricity and vice versa. If that's the case why can't we use magnets as batteries, and why aren't my batteries magnetic?
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### Amplitude of voltage from centre tap rectifier?

Should be the amplitude of voltage obtained from a centre tap transformer be about half if not rectified? Because in centre tap the potential difference for each half cycle is taken a cross only half ...
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### Wind turbine design question [closed]

I am planning to design a wind turbine that is has rotor blade radius of 0.915m and is connected to a generator. The generators specifications are, it is an ac generator with 5000 coil turnings and a ...
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### Is the electric field strength along an equipotential surface constant?

I'm trying to determine whether or not the electric field strength $|\vec{\mathcal{E}}|$ is constant everywhere on an equipotential surface. I know an equipotential surface is defined as  S = \{\...
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### Can current be induced in a grounded conductor?

I'm engaged in a rather lively debate with a group whose physics I believe to be a bit shaky. Basically they're claiming that if a conductive object is grounded to earth, the current cannot be ...
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### Do electric and magnetic lines of force physically exist?

As per my imagination any thing can't impose force on the other by not giving even a touch(i,e action at a distance). So I thought there must be some physical existence of lines of force. Although ...
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### Voltage without charge

Can a non-moving charge still have a (nonzero) voltage level? Basically, if i(amperes, measuring current)=0, does V(voltage) have to be 0 too?
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### Why does alternating current change direction? [closed]

As the title implies, I would like to learn why. I have read wikipedia pages in 3 different languages, searched the net and found nothing. Thanks in advance.
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### Why are some Air Gap Sparks Orange?

While testing the ignition system on my car with a variable gap spark tester I noticed that the spark was orange. I suspect that there may be a problem with the ignition coil such that there is ...
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### ionisation of gases by electrons

In canal ray experiment, how do accelearating electrons coming from cathode knock out electrons from the gaseous atoms in the discharge tube and thus ionise them ?what is happening exactly when an ...
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### What is the voltage of an average carpet static shock? Can you make it lethal?

I think I heard somewhere that it was in the thousands of volts, but it had extremely, extremely low amps. Could you somehow transform the current to make it larger or something? Or does the equation ...
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### Why are metals worse conductors when heated?

When metals, (such as in circuits), are heated, their ability to conduct electric current is hampered. Why is this? Does the transition towards liquid disrupt a metal's ability to conduct, or is ...
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### Temperature dependence on conductivity of a metal in terms of band gap, conduction band, valence band,

I am trying to find an answer to the following question: Why did the conductivity of one of the metals decrease with increasing temperature? Explain in terms of ...
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### I got an electric shock from a metal door…but no one else did?

Earlier today I got shocked 3 times by a metal door that didn't shock anyone else. The door (to a convenience store) is glass with a metal grate built in, and a metal handle and edges. I touched the ...
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### How can there be a voltage when there is no current?

I'm told at school that the Electromotive Force (e.m.f) of a battery equals the potential difference between the terminals of the battery when there is no current. How is that possible? How can there ...
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### 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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### How electrical energy is transfered trhough a wire, and what's flow of charge?

I've read these texts about misconceptions about electricity. This is my understanding: Electrons do move, mut slowly and randomly. What happens is that, in fact, they're just 'conducting' the ...
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### Why isn't there short circuit in a Mylar conducting sheet?

Basically, we use probes connected to a ammeter to outline equipotential lines. I don't know why it's ammeter not voltmeter. Think it's because if there there is no potential difference, there won't ...
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### How does the earth wire work? [duplicate]

Since we say when the live wire touches the metal casing of the appliance, the appliance gets live and touching it we feel a shock. Now let's think about the same situation having a earth wire. Here ...
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### If air cannot conduct electricity, how can lightning happen?

If air cannot conduct electricity, how can lightning happen?
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### Creating electricity from mains water pressure.

Could someone cleverer than me help me out? I had a crazy thought going through my head the other day and I can't lay my mind to rest until I get an answer. Q. How much energy could be produced by ...
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### How much current travels transversely in a coil ?

Excuse the the cryptic q. I was just wondering, say in a guitar pickup or AC transformer, we have a coil of copper wire that is coiled around a magnetic core(s). Current is induced in the wire by the ...
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### How to know what materials are good conductors of electricity?

I'm not asking a question like "Is the wood conductive?". No. I'm asking what properties do they have to have to be good conductors. Theoretically I mean.
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### What material used in soil based microbial fuel?

I have seen from wikipedia that there are soil based microbial fuel which need only anode and cathode while soil itself could act as proton exchange filter But what kind of other material it needed? ...
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### power in an ac circuit - difference between in series and parallel

In AC-circuits, we have different kinds of power: active power $P$, reactive power $Q$ and apparent power $|S|$. Let's say we have a circuit with a resistor $R$ and an inductor $L$. My understanding ...