Questions tagged [electricity]
The study of the presence and flow of electric charge. Charges, currents, fields, potentials.
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Divergence of electric field for point charge at origin
I'm aware that I've likely made a very simple error/misunderstanding here, but I have some confusion about the divergence of an electric field of a point charge which should be zero at all points in ...
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Does current flow equally through the cross section of a wire in DC?
(Most Probably a duplicate, but I couldn't find it)
I have heard about 'Skin Effect' in AC, but currently Im only and only concerned about DC.
When current flows in simple DC circuit, does the current ...
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Why won't the bulb light? [closed]
Here's what the marking scheme says: "Capacitor gets charged first and acts as an insulator/blocks current".
However, electrons flow from negative to positive, so shouldn't the electrons ...
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Electric field definition
In my book it says that "electric field" is defined as the "force per unit charge". What does the "unit charge" mean? My initial thoughts was that it meant 1 Coulumb, but ...
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How to boil 40ml of water using a solar panel of 15v and 1amp? [closed]
I am making an application to use in third world countries where there is unlimited sunshine
I need to boile a very small amount of water, up to 40ml, using a solar panel that generates 15v and up to ...
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How can a surface charge create field on itself? [closed]
How is the surface charge creating a field on itself ?Grifith has put me in confusion.The example 4.8 of electrodynamics by Grifith shows that the bound surface charge is partly due to the field of a ...
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Is this approach of calculating mutual induction from magnetic flux Ok? [closed]
Coursework from Khan Academy, Electromagnetic Induction, - Mutual Induction worked example. For context video link - Mutual Induction Worked Example Link
Doubt link: - Image of the solved question ...
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Motor Effect Experiment
I recently saw an demonstration (image below) where the motor effect was being shown. They used the fact that forces come in pairs (Newton's third law) and so when current goes through the copper rod, ...
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Why is there a difference in potential across a component (potential difference)
I understand that potential difference is the difference in the potential across a component.
This is the difference in the amount of (work) energy it takes for charge to be moved across the component....
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Energy conversions in Electric furnace
Heating furnaces use eddy current to work, but I have a problem understanding something, what are the energy conversions that happen in the electric furnace? Is it magnetic->electric->thermal or ...
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Why do electrons dissipate all of their potential energy in resistors instead of storing some part of it in them as kinetic energy? [duplicate]
Suppose there is a circuit with one resistor and one voltage source.now we know that if the voltage souce is ideal then electrons will dissipate all of their potential energy while moving through the ...
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Effect of solenoid on iron core in ac and dc circuit [closed]
If i have 2 insulated coils and i wrap each one of them on a iron core (i have 2 seperate ciruits) if i add a dc source “battery” in the first circuit and an ac source in the second circuit would ...
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If the electrons leaving and entering the battery per unit time is different during transient phase then how it's voltage doesn't change?
I am a high school student and I am very confused in how battery's and electricity actually works?
My question is: suppose we have an ideal battery, we know as soon as we switch on the DC circuit, a ...
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How do electrons get kinetic energy in a circuit? [duplicate]
Consider the following circuit with its switch closed.
Electrons start moving from the negative terminal and then move throughout the circuit, I have two questions.
From where do these electrons get ...
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Potential drop against internal resistance of cells in combination
Suppose two cells of emf and internal resistance e1, r1 and e2, r2 respectively are connected in series. The negative electrode of 1st cell is connected to negative electrode of the second cell. Why ...
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Why is electricity so sporadic in it’s movement, when solids, liquids, and gasses, are usually straightforward?
Basically Newton’s second law states an object will remain in the same trajectory unless acted on by another force. what forces are acting upon an electric arc when it makes a jump between wires? or ...
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How does a large resistor in parallel with a thermistor affect the voltage-temperature graph curve?
I want to know whether my understanding of the thermistor being in parallel with a large fixed resistor is correct. There is another resistor in parallel with the thermistor but that is fixed and not ...
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Will a computer itself consume any energy if placed under super-conducting conditions?
By definition, any electronic circuits placed under super-conducting conditions (very low temperatures) will not dissipate energy to the surroundings as the resistance is 0.
If a computer was placed ...
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WIll maintaining the ratio of 'Voltage/Resistance' violate Ohm's Law?
In an ohmic conductor if voltage and resistance are increased in a constant ratio, the current will remain same and if it remains same, won't it violate the Ohm's Law?
As because Ohm's Law states '...
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What is the max distance between two conductors in vacum to close electrical circle [duplicate]
Assuming having one wire connected to the + side of a battery and another one wire connected to the -, what is the max distance between the wires so electricity will still flow from - to the + . Is it ...
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Why doesn't coil in an Ac generator not get deflected in accordance to the flemming's left hand rule when current starts to flow through it [closed]
Why doesn't coil in an Ac generator not get deflected in accordance to the Flemming's left hand rule when current starts to flow through it.
When the coil is ...
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Do attracted to electrode charged particles make current?
Consider a bulb with an anode. Cathode, is out of bulb.
Bulb is filled with gas.
Now, gas molecules are ionized by, for example external radiation.
Bulb should now contain "free" electrons, ...
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Would it be possible to create a compact and discreet static electricity generator that would induce a positive charge in a person?
I am wondering if it would be possible to create and use a static electricity generator that would induce a positive charge in a person. The primary purpose of this would be to repel small water ...
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Why is a powersource characterized by voltage?
Why is it that powersources are characterized by their voltage? If we are given a power source with a certain voltage we know that the potential difference per charge will be constant, and it will be ...
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Electric field and potential in Möbius band
Suppose I have a Möbius band with uniform density charge $\sigma$. ¿What would happen since is not possible to find the electric field or potential in its surface as:
$$ \vec{E} = \iint \frac{K_e dq}{...
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How do I calculate the distance between one atom to another in a cooper conductor? [closed]
Regarding the atomic model which free electrons are moving from one atom to another, I want to estimate the distance between those atoms
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Current in a Nonuniform Diameter Wire
According to the text Current depends on Area, but then in problems with a "nonuniform diameter" we say that the Current does not change even though the Area changes.
I think I understand ...
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Power equation in transmission lines [duplicate]
In transmission lines we increase the power to "reduce energy loss in the form of heat". Can someone explain exactly how and also I understand that we have to keep our power constant ...
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Pushing air downwards using a fan, to hover in air
I believe that I am simply missing something over here, but cannot find it.
I want to just think theoretically, that if I use a fan (drone manner) to push air downwards, like a rocket, I would be ...
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Experiment describing superconductivity discovery [duplicate]
We study in Ohm's law that current $I$ is directly proportional to voltage difference $V$ between two points, where resistance $R$ is the proportionality constant.
In 1911, if K. Onnes measured ...
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Why doesn't the landing of birds on powerlines ever lead to sparks like a Van der Graaf generator? [duplicate]
I saw a Van der Graaf generator spark when a demonstrator touched it. I believe the voltage was 600 kV which is in the range of high voltage power lines. Other discussions about birds on power lines ...
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If you have a negatively charged plastic rod, what will the direction of the electric field be?
A task by my professor includes a negatively charged rod, and he says the direction of the electric field should be in the direction of the radius of the rod--that is, outward! But we learned ...
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Does the presence of a disconnected coil nearby affect the self-inductance of a coil under test?
Picture two coils in close proximity. They have the same dimensions and are located co-axially, with a small gap between then (like Helmholtz coils, but much closer together than in the standard ...
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Finding the Magnetic Field within a solenoid
So, I have to find the magnetic field within a solenoid such that the field at a point(on axis) is half than that it would be at the centre. Length of the solenoid is 20cm and the current through it ...
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What is the microscopic physics of DC voltage propagation?
When a battery is connected to a circuit the voltage appears to the circuit as half a pulse and is propagated as an em wave, as any other pulse would be. This em generation must be the result of ...
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How do electric fields in circuits exactly work?
I have been introduced to circuits and told that an electric field, along with a emf provided by an external source (which can't be electrostatic), causes electrons to move. They follow the direction ...
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Short circuit on one branch of parallel connection [closed]
I don't understand how that extra branch that starts in (a) affects the circuit. If R4 did not exist, then r2 and r3 would be ignored but now you have to take into account the (b) knot. How can we ...
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If you put a magnet inside a coil and spin the surface they both are over, will this generate electricity?
A changing magnetic field induces an electric current in a coil. If you cross a magnet through the coil it will induce a current, but if the magnet is at rest relative to the coil there will be no ...
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What is the difference between ionic conductivity and electrical conductivity in an electrolyte?
If we apply an AC current to a conductor it creates an associated alternating magnetic field around it. That's the theory. Additionally, when a current passes through the conductor, there is some ...
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Electric Furnace Temperature Theory [closed]
I am designing a small melting furnace using 120VAC with an ideal maximum current of 10A. I'll be using Kanthal A-1 resistance ...
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Should I put my freezer in the middle of the living room? [duplicate]
There is a freezer in my kitchen. It has frozen fish fingers and spinach and potato waffles and leftovers. The food stays below freezing temperature using the principle of latent heat. The freezer ...
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Charge in a capacitor circuit [closed]
Firstly switch K is being closed and that one capacitor is being fully charged. Then the switch K is being opened again. What will be the difference of total charge in the system before and after ...
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Experimental realization of rectangular potential barrier
I was reading a QM book where they put the following figure aiming to explain how to realize experimentally a potential barrier/well. In the left (barrier) and right (well) plots they show a circuit ...
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Is there a formula describing corona effect that naturally occurs during storms?
Imagine we have a tree during thunderstorm. Due to electric field in the atmosphere, a corona discharge appears on top of it. My question is: is there a formula describing this effect?
I've already ...
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Confusion involving the energy stored on a capacitor
In A-level physics, one is told that:
The energy stored in a capacitor with charge $Q$, capacitance $C$ and voltage across the plates $V$ is: $$\frac{1}{2}\frac{Q^2}{C}=\frac{1}{2}QV=\frac{1}{2}CV^2$$...
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In a van de Graaf generator, when a spark happens, is an electromagnetic wave produced? If yes, in which direction?
In a van de Graaf generator, when a spark happens, electrons moves from one globe to the other globe.
Is an electromagnetic wave produced?
If an electromagnetic wave is produced, why is it produced?
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Resistance across different terminals of a material of variable resistivity [closed]
I have seen many questions in my book trying to find Resistance across different materials of variable resistivity(by integration).
For example, consider the following :
I can find resistance across ...
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What provides the centripetal force for Cooper pairs flowing in a toroidal superconductor?
What provides the centripetal force for Cooper pairs flowing in a toroidal superconductor?
I asked myself this question, which led me to realize I also don't really know the answer to a more basic ...
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Can we create energy from car tires using moving electrical charges?
Suppose that we put electric charges in car tires. Now when we drive the car, the charges will be moving on a circular path, viewed from the reference frame of the car. Therefore, they create a ...
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Current returning to wire when passed through earth
Consider the following circuit:
I have a bulb connected to a battery and then the wire as shown is earthed from two points. Now, since across the bulb potential difference will be zero, no current ...
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