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

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2answers
43 views

Why does a rotating aluminium disc slow down when a current carrying coil with iron core is held above it?

What I don't understand is it the Emf induced that slows down the disc or is it a force.
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1answer
27 views

High Voltage Powerlines - clarification of energy loss

I've been having a bit of trouble understanding the High-Voltage powerlines. If I was sending power from $A \rightarrow B$, we have: Ohm's law $V = IR$ Power lost in the form of heat $P = I^2 R$ ...
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3answers
829 views

Does electricity have an associated entropy?

One can certainly measure entropy changes associated with the generation of electricity, but does electricity itself have an associated entropy (maybe related to voltage, current etc.)?
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1answer
48 views

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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1answer
95 views

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 ...
0
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1answer
28 views

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 ...
0
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1answer
35 views

charge on the capacitors

When we connecting a capacitor to a battery of $V$ volts. After it is completely charged, it is disconnected from the battery, and if we connected to another capacitor. In this case, there is no ...
-1
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2answers
278 views

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 ...
0
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1answer
64 views

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 ...
2
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2answers
111 views

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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1answer
36 views

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 ...
0
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1answer
123 views

Basic concepts of electrostatics

How to deal with a grounded conducting sphere (I.e finding charge on it) in uniform electric field ? And if any two charged conducting spheres are in each other's electric field then will ones field ...
1
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2answers
56 views

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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0answers
24 views

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 ?
2
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2answers
44 views

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 ...
0
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0answers
9 views

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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0answers
47 views

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 ...
5
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1answer
63 views

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 ...
1
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0answers
22 views

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?
0
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0answers
21 views

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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1answer
49 views

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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1answer
51 views

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, ...
2
votes
1answer
32 views

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 ...
1
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0answers
40 views

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 ...
4
votes
3answers
266 views

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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0answers
49 views

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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0answers
45 views

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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1answer
27 views

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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1answer
66 views

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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0answers
16 views

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 ...
2
votes
1answer
41 views

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 ...
3
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2answers
56 views

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 ...
0
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0answers
14 views

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 ...
1
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1answer
30 views

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 ...
0
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0answers
54 views

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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0answers
14 views

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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3answers
103 views

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 ...
0
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1answer
13 views

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 ...
0
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0answers
16 views

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? ...
0
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1answer
45 views

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 ...
-1
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2answers
74 views

How could a solar eclipse cause my light bulb to explode? [closed]

Any explanation to this? as it happened right during the phase of eclipse or is it just coincident? I had just finished my breakfast and on the way to go outside to watch the eclipse and before it ...
1
vote
1answer
18 views

Does electron drift model apply to current in liquids

The electrons in a metallic conductor, tend to drift at abysmally slow speeds, but still a current is able to flow through it, because the net movement is in the direction of the applied emf. How is ...
0
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1answer
34 views

How does the jumper in Christmas lights work?

This is the structure according to my textbook: I don't know what the glass insulator are for?? But there is indeed a thin layer of insulator coating on the jumper. Why I don't know, too, what that ...
0
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0answers
193 views

Electric Honeycomb [duplicate]

Set a vertically oriented steel needle over a horizontal metallic plate. Place some oil onto the plate. If you apply constant high voltage between the needle and the plate, a cell structure appears on ...
0
votes
0answers
9 views

Discharge Static Electricity from Carpet without chemicals

I've got a large amount of static electricity built up in a room. Is there any way I could discharge the static without the use of chemicals?
1
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2answers
76 views

How can the fact that there is no electric field inside a hollow conductor be explained by Faraday's ice pail experiment?

Basically something very similar to these pictures These are from two separate books. The bottom picture says that all the excess charge in an object can be transferred to an already charged metal ...
1
vote
1answer
223 views

Why don't we feel shock when there is lightning? [closed]

When there is lightning in the sky and I am are standing on the ground having no insulating material between me and the ground, why do I not feel an electric shock? If this looks stupid to you I am ...
2
votes
1answer
32 views

What are the clicking sounds when static electricity occurs?

Sometimes, when there's static electricity, soft clicking sounds can be heard. This may happen when two fabrics are rubbed or when you get a static shock. What exactly causes this sounds?
0
votes
1answer
29 views

Proving an AC current with peak amplitude of 311V is equivalent to a DC current of 220V [closed]

If one starts with an alternating current in the form of a sin wave with a peak amplitude of 311V and then goes through the usual RMS procedure of integrating $sin^2$ from 0 to 2$\pi$ then the result ...
3
votes
1answer
70 views

What phenomena occur in a low voltage arc between copper and graphite electrodes, and why is the result dependent on electrode polarity?

I was playing around with a laboratory power supply, drawing arcs between electrodes of various materials. I noticed phenomena that I found interesting, and couldn't really explain myself: The ...