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

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5answers
2k views

How does a wire carry alternating current?

Consider a simple network of a bulb whose two terminals are connected to two wires with open ends A and B respectively A o--------💡--------o B Now if a DC ...
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3answers
59 views

What is the voltage in this circuit? [closed]

Attached is an image of circuit diagram for which I was asked to calculate the voltage for. However, because of the lack of information provided I belive this is impossible. Am I correct?
3
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1answer
84 views

Constant charge in special relativity

We had special relativity introduced in our course and used it to derive some facts. At one place we used the fact that if in frame of reference $U$ the electron has charge $e$, then it also has ...
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2answers
39 views

What does it means to say an electric charged person has a higher potential voltage compared to the door?

I'm studying electric potential energy and its defined as the energy needed to move a charge inside an electric field from a point $a$ to $b$. Then, it defines electric potential energy per charge, ...
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2answers
125 views

Will a bulb glow brighter if voltage is increased but current remains the same?

I understand that increasing voltage increases the energy given to each coulomb in the circuit, so in theory more energy given to a bulb should make a bulb glow brighter. But also if voltage is ...
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2answers
67 views

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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2answers
153 views

Why do metals become insulators when oxidized?

I don't know the connection between how forming a new bond with oxygen then changes the density of states to transform the metal into an insulator. It seems like a very powerful transformation.
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1answer
25 views

Does the alternating current “move” such that there can be Lorentz force present on the wire?

As in question, does the alternating current "move" such that there can be Lorentz force present the wire? Becuase the current alternates on a fixed place there can be no Lorentz force?
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1answer
23 views

how the current steadily flows due to motional emf?

In motional EMF, the positive charges (current) flows from higher to lower potential. If this is the case, then the current should stop at the point of lower potential. But this does not happen - the ...
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3answers
91 views

How does an ammeter in a circuit work?

Apologies for this simple question, but I'm having trouble grasping the concept of how an ammeter works. Taking the following circuit as an example: When the switch is closed, current flows ...
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1answer
56 views

Why is it necessary for a circuit to be complete?

Can electrons not flow through a load if they do not have a path to flow to the positive terminal of the battery? Why is it absolutely necessary for electrons to end up at the positive terminal?
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2answers
82 views

In a circuit one light-second long, does it matter where in the circuit the switch is placed? [duplicate]

I was looking at this textbook example that was posted to reddit: The accompanying comments basically thrashed it saying everything was wrong. I had a specific question about it, though, and this ...
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2answers
55 views

Can electricity flow in a sufficiently large insulator? [closed]

We know that electricity cannot pass through glass and wood. but what if we decrease their resistance? We can do so by taking a very broad cylinder (high diameter) because $$R= \frac{\rho L}{A}$$
0
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1answer
33 views

Is “applying a voltage” the same as “applying a potential” to an electrode?

From what I understand, voltage is the potential difference, but it seems like the terms are used interchangeably. This is confusing me because I am only just learning what these terms mean. I'm also ...
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0answers
19 views

Could Nikola Tesla's idea of “using Earth as the medium for communication and power delivery” work?

According to the "Feasibility" section of the "World Wireless System" article on Wikipedia: "opinion amongst Tesla proponents ranged from the idea not being practicable to claims some of Tesla's ...
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0answers
42 views

Distance of the electric field generated by a Slayer Exciter ( Variation of tesla coil )

I'm currently trying to create a really basic simulation of a slayer exciter for a demonstration I have to give at my college. The thing is we want to know how far does the electric field produced by ...
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1answer
47 views

Can we produce a wave by oscillating current? [closed]

If Radio waves can be generated by using oscillating current so if we changed the properties of current to produce less wavelengths or light waves - I'm not asking about the possibility of producing ...
0
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2answers
72 views

Charges on capacitor after full charge by battery

When the charging is finished what will be the charge on an ideal parallel plate capacitor ? To be specific what are the charges on different faces of the 2 plates ? All the books say, after 100% ...
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1answer
81 views

Why does transformer winding need large numbers of turns?

In transformers there are large number of turns in winding for both primary and secondary sides around the core. So, my question is why can not we just put one or two turns in winding as we need to ...
3
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4answers
93 views

Avoid static electricity shock on treadmill

I've recently started getting shocked from the treadmills at the gym whenever I touched the buttons on their console. It's getting seriously hard to use them because the shock is not mild it's rather ...
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1answer
24 views

Difficulty understanding the energy transformations during resistance in a circuit

I am currently having problems understanding the energy transformations that occur when resistance in a solid conducting wire restricts current flow. From my understanding, resistance in a solid ...
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1answer
70 views

A confusion with solenoidal windings

I have seen in solenoids, toroids, transformers, electromagnets and machines that the core is pretty insulated. Over this the winding coil is wrapped but it is a bare coil (turns are not insulated to ...
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1answer
39 views

Transfer of electrons and static electricity

From what I currently understand about static electricity, electrons "jump" from one object to another, which object loses electrons depends on where it falls on the Triboelectric series. For example ...
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0answers
14 views

Are the effects of faraday's law of induction worth considering in this experiment?

In my intro to physics lab at uni, we did an experiment where we were supposed to measure the amount of kinetic energy and momentum before and after collisions between two carts. For some reason, ...
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1answer
20 views

Short Circuit Fires

I understand that if there’s low resistance, Ohm’s law shows that the current drawn will be very high. However, isn’t resistance what causes heat in a wire? I get there’s a lot of current going ...
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3answers
32 views

Open Circuits vs. Charging a Capacator

When you attach a capacitor to a battery via two wires, charge transfer occurs from one of the plates to the other. However, in an open circuit, there is infinite resistance in the dead-ended wire, ...
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1answer
20 views

How many electrons pased in electrical circuit

Assume I have electrical circuit that is connected to 5V power supply and current straight is 1A. How to know how many electrons are passed in single point per hour?
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1answer
38 views

If I lick a 9V battery, why doesn't my tongue noticeably get hotter?

Power dissipated is I^2*R, I don't know the resistance of my tongue so I can't tell how much current goes through my tongue. A resistor I have does get hot and I'm guessing it has a higher resistance ...
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1answer
27 views

Power with varible resistance

I know that P=VI, but what i was thinking about is that if we kept the voltage constant and increased the resistance, we will have less energy consumed by the resistance per second. So, this seems ...
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3answers
51 views

Current and resistance

Why the current is the same at all of the positions in a series circuit??,although there are different voltages at different positions of the circuit. What i know is that as the electron passes one ...
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1answer
10 views

Passive cathodic protection

Trying to understand what is happening when we need protect peace of Fe by placing on it more active metal (for example Zn) like ...
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0answers
25 views

The change of length of positive column in glow discharge

When I was doing the experiment of glow discharge, I lowered the voltage between electrodes and find that the length of positive column will increased quickly around a certain voltage(the interval of ...
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0answers
28 views

If a heater was turned on its' own wire, would heating of the wire cause the resistance to increase, thus the current into the heater to decrease?

I'm thinking not, because; A) It wouldn't make much sense in the real world because you'd need to avoid ever turning a heater towards its own wire, and you'd have to regulate the temperatures of any ...
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1answer
34 views

Did I calculate this voltage correctly?

I have just started to learn physics. Please forgive me if I am completely wrong or something, I have just turned 14 haha. I am trying to learn about how to work out voltage for my year 10 exams. ...
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1answer
43 views

Could someone simply explain how a railgun works?

Could someone simply explain how a railgun works? What could possibly accelerate an object that fast in such a short distance? I've heard it has to do with current between two rails, but I simply do ...
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1answer
44 views

Thevenin theorem

Hi i got the trouble and i miss the concept about v out in thevenin i have the circuit like this so i used voltage divider for finding the voltage at point 1, but how to finding voltage at Vo , ...
8
votes
8answers
324 views

How do electrons know when a circuit is closed?

I was told that electrons do not begin flowing unless the circuit is closed. The electrons from the battery are not in the ends of wire when it is open, apparently, as there is no reason for them to ...
0
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1answer
37 views

How soon would electrons start flowing once I closed a switch on a circuit that was one light minute away from the battery

In a circuit, how do electrons "know" when the circuit is closed? To my understanding, they do not start flowing unless the circuit is closed. How soon would they start flowing once I closed a ...
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0answers
15 views

Hollow metallic waveguides versus optical waveguides versus cables

In almost every physics program, you learn about electricity, electromagnetism, photonics, ... Within the electricity course, you learn about transporting electric energy as electrons through cables. ...
3
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2answers
140 views

What happens in circuits where the propagation time of the electric field is significant?

Kirchhoff's current law assumes "that whenever current flows into one end of a conductor it immediately flows out the other end". I want to understand what happens when we cannot make this ...
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0answers
24 views

What happens to the electrons at junction?

In a Closed circuit at any wire junction, one end of a wire is bound to an end of another wire . Now the Circuit is closed. So the electrons are passing through the wire. Now at the junction there is ...
2
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0answers
63 views

Why does the characteristic curve (V vs I) for a light bulb backbend?

When teaching Ohm's Law, I have students do an exploration of a small, incandescent light bulb with a low frequency (1-2 Hz) sine wave. It's a simple series circuit of source and light bulb, ...
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3answers
72 views

Speed of electricity in cable [duplicate]

Movement speed of electricity in cable, is same as speed of light in space? In other words, electricity moves in usual electro cable aproximatelly 300 000 km/second ?
0
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3answers
63 views

Why does AC induction motor rotate the same way?

Suppose an aluminium disc is suspended where it can freely rotate. A magnet is placed above (not touching) the aluminium disc and made to spun. This obvious causes a changing magnetic field. By ...
0
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1answer
35 views

Why does not the electrons in a conducting the wire end?

What happens to the electrons in a conducting wire, Why does not the electrons in the wire end? I have read answers on the web but have not manage to understand, the free electrons from the ...
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1answer
32 views

Can we use a photon to use it as a changing field in an electric generator? [closed]

In an electric generator we use a changing magnetic field to create electricity. But what if we use a photon's oscillation of EM waves to generate electricity in a metal wire as we do in an electric ...
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0answers
22 views

Would it be possible to transform power using capacitors instead of coils?

Would it be possible to use capacitors to transform electrical tension (up or down), in the following way? Let's say you have a 10v battery, and you want to transform the tension up to 40 v. First, ...
0
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1answer
56 views

Why is the resistivity of a copper cable much higher than copper?

I was looking at the data sheet for a copper cable and noticed the conductor resistance to be specified at around 5 mOhm/m. This is magnitudes higher than pure copper, which has a resistance in the ...
5
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1answer
84 views

Does a Tesla coil work in space?

If I took a Tesla coil into space, and then turned it on near, but not touching metal objects- would charge jump to the metal objects? It's my understanding I wouldn't see a flash, since the lightning ...
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1answer
67 views

Will a small magnet affect an insulated computer wire?

I'm designing something that involves a small magnet, probably about 0.5m in diameter, which will rest next to a computer wire carrying data, video, audio, etc. If the wire is insulated (think USB or ...