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Questions tagged [electricity]

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

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Does the cold affect electrical conduction?

Disclaimer: I'm not experienced in many phyiscal nor electrical terms and I have no idea where to ask this question elsewhere. I'd be open for a move request if needed. Today when using public ...
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122 views

Am I positively charged or negatively charged?

We often hear that the human body has a weak electrical charge. Is it a positive charge or negative charge? Or maybe different parts of me have different electrical charges? Or maybe there's a ...
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How do scientists determine the width a thunderbolt?

As I searched on the internet, I found a website stating that the width of a typical lightening strike is $2.5~$cm wide and $8$ km long. I intuitively understand that scientists can measure the length ...
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Would it be possible to conduct electricity using laser-ionized air?

If you had a high-powered laser and shined it through the atmosphere - causing a large amount of blooming and ionized air/plasma - could you use this as a conductive channel? I'm imagining a kind of ...
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What are some differences between electric force and gravitational force? [closed]

What are some differences between electric force and gravitational force? I mean, electric force is stronger, and electric force can be neutralized, but what else is there?
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Why don't insulators conduct electricity? [on hold]

I have been taught in school that because of the high energy band gap (approx. $9~\text{eV}$ or more) of an insulator, electrons can't jump to the conduction band. But also $1~\text{eV} = 1.6 \cdot ...
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31 views

How to measure an electron plasma with an electrically biased probe?

I want a crude way to confirm the existence of an electron cloud in a moderate vacuum of 2 mTorr. In my set up, filaments emit electrons into a magnetic trap which concentrates them (similar to an ...
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36 views

Electron waves through conductors

I'm not a student, professor, or academic scholar so please excuse me if this question seems "amateur". I'm very curious about how electricity, magnetism, and frequency all work together. From my ...
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42 views

Phase angle of current in AC circuit

Considering an AC circuit with a capacitor. I learnt that the current leads voltage by a phase angle π/2. This means current starts before voltage. But I learnt that current doesn't exist without ...
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1answer
18 views

Ratio of charges between capacitors in parallel and in series [closed]

Context: this is a multiple choice question, but no explanation is given Question: three capacitors of equal capacitance are connected in the following circuit. Determine the ratio of charge in ...
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32 views

why doesn't EM waves get weaker as we travel further away from the source [duplicate]

I know that as we get further away from the charge or from the magnetic field source both magnetic field and electric field decreases ,so why don't electromagnetic waves get weaker as the travel ...
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1answer
42 views

Is there any way to determine how long a wire is?

This is for transmission lines applications. Are there any way to know how long the wire like by getting the resistance of the wire(but how). Or is it possiblee to charge the wire until it produces ...
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Circuit problem with different resistors and analysis of voltage of electrons

So when I was learning electricity I had this confusion: assume there are 2 circuits, first is connected a resistor with very high resistance, second is connected to a resistor with very low ...
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52 views

Which explanation of the Seebeck effect is correct?

I have just begun reading about thermoelectricity. However I’ve been struggling to find a satisfying explanation for the the thermoelectric effects, specifically the Seebeck and Peltier effect, The ...
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36 views

Large objects in the universe sized by gravitational and electrical constants

In a famous talk (from 14:30 to 15:00) Nima Arkani-Hamed tells us that what "fixes the size of the earth" is the equilibrium between the gravitational pressure against the atomic pressure of the atoms ...
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46 views

Center tap transformer- How do we get voltages that are 180 out of phase?

I have been reading that in a center tap transformer, we get 2 voltages which are 180 out of phase. Can someone please explain how that happens.?
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3answers
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Why can't we have superconductors?

My book says, "Short circuiting occurs when the live wire comes in direct contact with the neutral wire, so a zero resistance path is provided to the current. A heavy current then passes through the ...
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25 views

Magnetic field at the center of a rotating charged square loop

Consider a square loop of side length $2a$, with a total charge $Q$ uniformly distributed along its sides (so that the line charge density is $\lambda=\frac{Q}{8a}$), set spinning at angular velocity $...
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1answer
51 views

How a spark is produced?

When we are closed to some metal sometimes spark is created. Is this because when we come close to a metal our charged fingers charge by induction the metal ? Then a voltage between our finger and ...
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1answer
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Why EMF induced in the coil acts to oppose any change in the magnetic flux?

This might be an absurd question for some of you guys. According to Lenz's Law an induced current will create a magnetic field that induces another current in which it opposes the current causing it ...
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1answer
31 views

At what pressure do semiconductors break down? [closed]

So let's say you were going to send some electronics to the bottom of the ocean, 3-5km down. This would be about $5km*1000kg=5Mkgf/m^{2}$. So at what pressure do circuit boards, transistors, etc stop ...
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1answer
35 views

What does it mean for an oven heating element to burn out?

The heating element in my oven has just burned out and I needed to replace it with a new one, because it simply wouldn't heat. When I took it out it looked pretty much OK (at least no huge difference ...
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2answers
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Does current flow when you connect a battery to earth?

Let's say that the earth has 0V and everything is ideal, does current still flow and why?
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Electrons and wires [duplicate]

The electrons that carry the electric energy are in wires or in the battery ? battery provides a potential difference but from where electrons flow to make for example a bulb light. If they flow from ...
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2answers
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From where electrons flow to make a bulb light?

Suppose we have the "basic" stuff like a battery 2 piece of wire and a bulb. Battery has a potential difference. But from where electrons flow to make the bulb light? from wire or from battery or from ...
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1answer
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Can electric potential be discontinuous?

I am studying the following problem, which is 9.11 of "Modern Electrodynamics" by Zangwill. The idea is that you have a wire attached to a perfectly conducting sphere (radius $a$) buried into the ...
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The flow of electric current

If positive charges have higher electric potential difference than negative charges then why the negative charges (electrons) are the one that are moving in a circuit? and to my knowledge the ...
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Is it true that conductors of electricity are terrible magnets, and vice versa? Why?

Certain metals, like gold, copper, and silver are excellent conductors of electricity, but make terrible magnets. Iron, nickel, and neodymium are excellent magnets but terrible electric conductors. ...
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What would happen if lightning struck a salt deposit?

I'm not familiar with the formulae involved in lightning discharge, so please bear with me here. As far as I'm aware, lightning (that is, cloud-to-ground lightning) tends to do one of three things, ...
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1answer
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Can we make a formula that describes the magnetic force as a function of electric field using length contraction equation ?

I know that the magnetism is just electricity and due to length contraction and the change in charge density moving charges experience what we call magnetic force. so my question is can we calculate ...
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Electrostatics question inquiry [closed]

The answer is C given that the left ball is positively charged. But since the sphere is heavily positively charged, shouldn’t the sphere repel the left positively charged ball rather than the left ...
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1answer
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Stack/Chimney Effect: a physical explanation on how height of chimney affects $\Delta P$

A fellow engineer told me that there are greenhouses which exploit the stack effect, in order to cover some or all of their electrical energy needs. This is achieved by installing small electrical ...
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3answers
126 views

Current in infinitely long wire? [closed]

Theoretically, suppose an infinite-length wire with completely no resistance (0Ω) connected to the terminals of a battery, and an electric lamp placed in the "center" of said wire. The question is: ...
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28 views

Hydrogen Sulfide New Superconductor? Is It Possible For Hydrogen Sulfide?

According to a very trusted science source : https://www.zmescience.com/science/news-science/superconductivity-artic-temperatures-05342/ There is now such thing as a Hydrogen Sulfide Superconductor ...
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$V = 4 volts$ but $I = 0$

Recently in my school, I tried to generate electricity from plants in a flower pot with copper and Zinc electrodes. The Potential difference in the voltmeter read 2 to 3 volts but when I connected the ...
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What force is responsible for the movement of electrons in a current caused by an electrochemical source?

From what I have read, batteries provide an electrochemical potential that causes electrons to move from the negative terminal through a conductor to the positive terminal. I have read numerous ...
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2answers
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Please help identify this physics apparatus!

This was my grandfather’s and have no idea what it is only that it is some piece of physics equipment! The main black cylinder doesn’t seem like it wants to rotate but not sure if it should?
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1answer
41 views

Can lightning bend metal?

If lightning strikes a metal pole, will it bend because of the force exerted by Earth's magnetic field on the current?
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What is the advantage of stacking the electrocytes? Of having the stacks side by side?

Electric rays (genus Torpedo) can deliver electric shocks to stun their prey and to discourage predators. The voltage is produced by thin, wafer￾like cells called electrocytes, each of which acts as a ...
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Why does the diameter of household wire affect the maximum safe current?

The greater the diameter of the wire used in household wiring, the greater the maximum current that can safely be carried by the wire. Why is this? Does the maximum safe current also depend on the ...
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2answers
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Is there a fundamental efficiency limit for generators?

Im currently interested in the theoretical efficiency limit of a generator, ie any device transforming kinetic energy to electrical energy. In particular, id be interested in turbines, that convert ...
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2answers
51 views

What is it about a light bulb that makes the resistence greater as the voltage increases?

I have a question on one of my physics labs that I do not exactly know how to answer. Question: Is the resistance for larger voltages greater than, less than, or equal to the resistance at smaller ...
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0answers
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What is the voltage breakdown of saw dust particle board?

I have done some testing for the electrical breakdown with the type of wood called particle board. But this particle board is made out of fine sawdust. So I guess what I’m asking is this. Question: ...
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2answers
17 views

Effect of electroplating on resistance

How will resistance of a wire be affected if I electroplate it with copper will it decrease ? And if yes then will the decrease be significant? I need to find a topic for my project I thought it might ...
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1answer
27 views

The direction of the electric field at a point on a diameter away from the center of a uniformly (positively) charged hemisphere

The answer is : perpendicular to the diameter. I don't understand how to arrive at that answer. I'm taking a high school physics course and have covered Electric field and Gauss's law for simple ...
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1answer
22 views

Hydrogen oxygen fuel cells

In hydrogen - oxygen fuel cell, the electrode used is carbon electrode.Hydrogen is passed through through the anode compartment where it is oxidised. Oxygen is passed through the cathode compartment ...
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A difficult mix between thermodynamics and electricity [closed]

Consider the device in the image.The cylinder has dielectric walls which do not permit heat change between the gas that is inside and the exterior environment.The cap A of the cylinder and the piston ...
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3answers
41 views

Does a filament's resistance increase as current through it decreases?

I'm confused about resistance's relationship to current and power. Scenario: CIRCUIT A 10 V battery 100 W incandescent light bulb Calculate resistance: I = P/E I = 100/10 I = 10 amps R = E/I R = ...
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1answer
25 views

Electric flux and electric field lines [duplicate]

Why we draw finite electric field lines passing through a surface when we can draw infinite ? also why electric flux is proportional to the number of lines passing through a surface ? i am confused ...
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1answer
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What is the equation for the electrical arc length of an arc that has been struck?

I have been experimenting with voltages at 2,320 volts AC. I am curious and haven’t found any equation to calculate the electrical arc distance that is drawn after striking an arc by touching the two ...