Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
4,084 questions
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What is resistance precisely?
Is there a mathematical definition for resistance because I cannot find any. On the internet I find definitions such as:
The electrical resistance of an object is a measure of its opposition to the ...
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1 watt of power defines as? [closed]
Imagine you have a light bulb of 1 watt power. Then, is 1 watt defined as
•1 joule of electric energy transformed to 1 joule of light energy in 1 sec?
•what exactly is meant by 'consumption' of energy ...
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Would it be possible to make a conducting cable out of water? [closed]
I know it may be dumb, but water is a good conductor of electricity. If it is even possible, would it be fast and how efficient would it be?
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What happens to current in a wire with a chunk taken out of it?
What happens to current when a the cross sectional area of a wire changes?
Here is what I'm visualizing:
A material with conductivity $\sigma$ is formed into a square wire with cross sectional area $...
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Speed of current at higher and lower potential [closed]
It is said that, charge has more potential energy at higher potential as compared to lower potential in an electric circuit. So, is the speed of current faster at higher potential and slower at lower ...
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Feasibility of Supercapacitor Design Using Etched Brass-Coated Copper Wires [closed]
I'm working on designing a supercapacitor and would appreciate any insights into its feasibility and potential challenges.
Design Overview:
My plan involves creating multi-layer coils where the anode ...
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If I throw a neutral conductor piece at the cathode of a high power battery; and after it bounces at me; will I get a current passing through me? [closed]
Yeah all I want to ask is in the title
Here is my thought experiment....
When the conductor piece hits the negative terminal a $\delta^+$ charge develops in the conductor piece and a $\delta^-$ will ...
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Can we light a lightbulb using Earth's electric field, if it was inside a medium with high charge density?
I know my question is similar to "Why can't we generate electricity from Earth's electric field?", but in that question the bulb is held in air, with terminals 1 meters apart. Here, light ...
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Why do I get two different efficiency values using $ P = VI$ and $P = \frac{V^2}{R}$? [duplicate]
I am solving a question about power transmission efficiency and encountered two different results using two methods.
The problem states:
An electric power line, having a total resistance of $2 \, \...
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Under what conditions will a circuit violate conservation of charge and/or conservation of energy?
Consider the following circuit diagram containing two capacitors and an inductor:
Suppose that $C_1$ is initially charged to some voltage $V_i$ and that $S_1$ is closed at $t=0$. If the switches are ...
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How is the electrical information within a biological system measured using simple wires?
I would like to better understand how electrical signals within biological tissues are measured using simple wires. On one end, the exposed wire tip is embedded within biological tissue (for example, ...
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What connection does the Lorentz force have with conductors? [duplicate]
So if I have a battery of two terminals, my understanding is that a uniform electric field will be created between the terminals.
The surplus of electrons on the negative side should then experience a ...
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Does a packed fridge cost the same as an an empty fridge? (Electricity cost) [duplicate]
Discounting initial power to bring an item into a frozen state, then is the electricity cheaper to leave my fridge empty; or is the cost the same for it being packed with frozen foods?
If my fridge is ...
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Why is electric flux different from the mathematical definition of flux?
Mathematically, the flux of any quantity $q$ that flows is defined to be
$$\frac{\mathrm dq/\mathrm dt}{\text{Area}}$$
However, electric flux is the scalar product of the electric field and area $E\...
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How to calculate the effective permittivity of a material exposed to an electric field of a square wave? [closed]
Sorry if this is more of an engineering question, but i think it fits the forum.
I want to calculate the capacitance of a capacitor which is made out of a comb like structure (compare the ascii art ...
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'Volatility' of electric charge on a balloon
It is well-known that if a charged balloon touches an electroscope, some charge is transferred. When the balloon is removed, the electroscope keeps that charge. But actually the balloon does not need ...
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Transient Charge Redistribution Within a Finite Conducting Medium
Consider a spatially finite region of conductor, with conductivity $\sigma$. Now imagine a net charge density $\rho$ spatially distributed throughout the volume of the conductor at time $t=0$. Usually,...
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Effect of electric charge on human body
I was reading some other questions when I came up with this.
People are often warned about the danger of electric currents passing through the body. Is charging the human body with a small current ...
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Is it true for every case? 'The induced charges and inducing charges have the same magnitude but opposite in sign' [duplicate]
The electron at the farther end (A) of the rod might have less impact on the electrons in the sphere, meaning it may not affect the sphere's charges. For instance, if five electrons are sufficiently ...
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What will Electric field be when the charge on negative side of Capacitor is changed? [closed]
One of the two parallel metallic plates is uniformly charged with charge $+q$, and the other one is charged with charge $-q$, the electric field between them is $E$. When the negatively charged plate ...
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Electrical Power and The Product Rule
As we know, the formula for Instantaneous Electrical Power is:
$$P(t) = I(t)V(t) $$
But, if work is expressed as:
$$W(t) = q(t)V(t)$$
And Power is the time derivative of Work:
$$P(t) = W'(t)$$
Then by ...
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What is the efficiency of a Franklin's Bells device?
Just sitting here day dreaming, and I had a hypothesis that a Franklin's Bells device is likely extremely efficient. Its mostly a gut feeling though based on its low surface area contact point between ...
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Electric circuits: voltage connection
The intuitive answer to this question is to connect the voltmeter in parallel to the battery. However, the official answer says: the voltmeter is connected to the right of the battery, between the ...
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Why metal objects (like a door, a desk, or a machine) get charged?
I work at the University in a office at the science building. At my workplace, every time someone touches a metal object (like a door, a desk, or a machine), they receive a small electric shock. This ...
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Electrical insulation properties of flexible magnets
What thickness of rubber or pvc, ferrite or neodymium, magnet is required to electrically insulate a 12awg 120v 20amp wire for general commercial usage?
Tables, charts, formulae for different ...
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Can we increase solenoid heat efficiency by cutting it on small rings?
Suppose we have solenoid with resistance $R$ that produces magnetic field $B$ and heat by passing current $I$ through itself.
Lets cut it on $n$ parts and connect them in parallel. Now per-ring ...
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Alternating Current versus Direct Current
I was given an $I$ v/s $t$ graph that looks like this:
Will it be classified as AC or DC? The current switches directions once, so not DC (current flow should be in one direction only). I don't ...
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Why is the conductance of an insulator not $0$?
Even diamond, water, etc. have a specific resistance value. So when sufficient voltage is applied, current does flow through them. But they don't have free electrons like conductors. Water conducts ...
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Does it take some initial extra energy to start a circuit?
I imagine before a circuit flows the electrons are still. Some work needs to be done to establish a current. Otherwise we just arrive at a situation where a battery gives 8 Joules of energy per ...
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Physical Explanation of Maximum Power Transfer
I have seen a lot of videos on this theorem but all of them prove it using algebra or calculus. When I tried to think of this problem in terms of the physical definition of power i.e energy ...
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Apparent mathematical contradiction regarding constant potential inside conductor - what am I missing?
I know that the electric potential inside a conductor is always constant, regardless of anything surrounding the conductor.
Mathematically, I don't see how this makes sense. Please consider the ...
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What I think about surface charges in electrical circuits
Assume We have a simple electrical circuit with a DC Source of constant emf.
And I am talking about the ideal case.
The circuit also consists of "Push-Key" or a normal switch whatever you ...
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Measure real corona discharge intensity, range 2000-7500V?
I need to measure the actual corona discharge intensity produced by a particular circuit and electrode array. I'd love numbers as hard as possible, though am not sure what units apply; alternatively, ...
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How do circuits work at a subatomic level?
I imagine it’s like this. Let’s say we connect a copper wire to a battery’s terminals. The electrons from the negative side will thus exert a push on the electrons near the wire and it will continue. ...
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Do wind turbines spin at constant speed? If so, how? [closed]
All electrical power fed into the electric grid needs to be an AC power source at 60 Hz (in the U.S.) to within a very tight tolerance.
My understanding is that steam turbines are kept rotating at a ...
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Why are electrons in a wire so slow and what exactly makes them move?
If one applies an electric field to a conductor, then the electrons inside it will start moving around, until the field is balanced out to 0. It is said in Griffiths’ “Intro to E&M” that this ...
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How Are Fractal Wood Burning Patterns produced by DC Electricity?
Here are 3 typical videos of fractal wood burning: video 1, video 2 and video 3.
As can be seen in all the videos, the different Lichtenberg figures develop simultaneously from both the positive and ...
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Why is there an electric field but not magnetic field on the LHS of the integral form of Faraday's Law
Just started to learn Electromagnetism, and didn't quite understand, please help correct my misunderstanding:
The lectures said that the electromotive force (e.m.f), was
$$
{\cal E} = \oint \vec{F} \...
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What is the formal definition of capacity fade?
https://www.ipaceforums.co.uk/threads/capacity-fade-vs-power-fade.6794/
According to this post capacity fade is defined as the percentage of total capacity left. So I'm assuming it would be calculated ...
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Curl of current density in a wire with variable cross section
We have a wire with the shape of a cone. The cone is aligned along the z-azis. Major radius $r_M$ and minor radius $r_m$ and length $l$. An electric current $I_0$ is injected at the bottom. We could ...
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Do flourescent tube lights create magnetic fields like other conductors?
So, does every electron flow also have a corresponding magnetic field to go along with it, or is magnetic fields only a property of solid metal conductors?
Also, what about lightning?
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Can you loop a charge pump?
Is it possible, to charge two capacitors in parallel(eg. each two volts). Discharge them in series to a third capacitor(4 volts). Charge the first capacitor again with the initial voltage(2 volts). ...
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Currently arguing with my teacher about this electromagnetism question, any helpers?
Sorry if my Q is simple, I'm still in high school.
I'm currently arguing with my physics teacher regarding a Q, shown below.
The answers state this.
However, I am attempting to argue that the ...
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What happens to the charges in an inductor when you induce a voltage?
Say you have two inductors, and - very much like a transformer - you connect the first one to a voltage source, then place the other one close to it, so that there will be an emf induced by the change ...
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How can I calculate the magnetic field of a plasma?
If I created a plasma and put a large electric current through it would a magnetic field be created? If so how large would this field be and how can I calculate it?
For example, we put 1000 amperes ...
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Will the electrical potential difference between the Windward and Leeward sides of a mountain range generate electrical current?
I would like to know if it is possible that the electrical potential difference between the Windward side and the Leeward side of a mountain range, due to a thunderstorm occurring on the Windward side,...
user300400
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Battery in non-closed circuit with charged body and Earth
Looking at the clips on how the battery works, I understand that eventually one of the ends releases the electrons which then move through the conductor to the other end, to continue the reaction. Now ...
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Could you make a fire torch with electricity? [closed]
Similar to a blowtorch, is there a way to generate a flame without using gas or liquid fuel(like butane, propane, etc)?
(source)
For example I'm thinking about those portable air heaters, could one ...
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Why electric field increase near the cable connected in AC 220V socket even current is zero?
If I put low frequency electric field meter near the connected cable in AC 220V socket, he show 1200 V/m even if device is turn OFF(zero current), if disconnect cable from socket, field drop to 8 V/m.
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Were radioactive materials used in neon indicator lamps? [closed]
Were radioactive materials used in neon indicator lamps?
Old-fashioned glow starters for fluorescent lighting
[How a glowstarter works]
often contain small traces of radioactive gas (like $^{85}$Kr or ...
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