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Questions tagged [potential]

Scalar and vector potentials in electromagnetism. The scalar potential is potential energy per unit charge. For potential energy, use the potential-energy tag.

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When the potential difference between two points in a circuit is zero, why is there no electric field between them?

I'm an electrical engineering student that's trying to become a bit more versed in the physics of electronics since so much of it is abstracted for us in our engineering classes. Anyways, I'm ...
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81 views

What are intuitive definitions of the 4 thermodynamic potentials?

So out of the 4 thermodynamic potentials only the internal energy seem to make intuitive sense to me. My understanding of enthalpy is that it is a state function which represents the total heat ...
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Distribution of potential within a capped cylinder

I need some help with calculating something. Lets say I have a hollow cylinder of length $2L$ and diameter $2R$. The electric charge density is given by $\sigma$. The potential going through the axis ...
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Conducting wire swinging in magnetic field

Imagine a situation where a conducting wire is swinging around one of its ends, in a uniform magnetic field that is perpendicular to the plane of rotation, and i want to find the potential that is ...
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Time-Independent Schrodinger Equation solution formulation (2nd-Order ODE)

Can someone explain the following for me please: $\bullet$ TISE, insider barrier: $(\hat T+V)u(x)=Eu(x)$ $-\frac{\hbar^{2}}{2m}\frac{d^{2}}{dx^{2}}=(E-V)u(x)$ Solution: $u(x)=Ae^{-\mathcal{ Hx}}$, ...
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Potential due to a charge distribution and multipole expansion

I'm studying on the Griffiths' book Introduction to Electrodynamics and a doubt came to me reading about the multipole expansion. In chapter 2.3.4 this formula is shown $$ V(\vec{r}) = \frac{1}{4\pi\...
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38 views

Voltage drop and voltage rise [closed]

Is the voltage drop the negative of the standard voltage (or potential difference)? Usually we indicate the potential difference with an arrow pointing against the direction of the electric field, i....
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23 views

Voltage as the work to move from infinity to a point in field

I understand that electric potential is defined as the work needed to move a charge from infinity to a specific point in the field. However, how does this apply for a field which is limited between ...
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Struggle in understanding the definition of voltage

I ask some help in understanding better the concept of voltage. The voltage is a difference in electric potential between two points $a$ and $b$. It is defined as $$V_{ab}=-\int^a_b\mathbf{E}\cdot d\...
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1answer
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how to calculate work done in moving a charge, when the path and point charge don't lie on one line?

Problem: A charge Q in point O=(0,0) and a test charge q in point A=(4,1) lie in a plane. How much work W needs to be done to move q to point B=(2,2). Q always stays at (0,0). Q=q= 2*10^-4. One ...
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Current through a resistor

My question refers to the image below: From what I have previously thought, in order to calculate current through a resistor you would use Ohm's Law, meaning you get the voltage across the resistor ...
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Deriving potential from central force [closed]

I've read in a book that for a central force of the form $$ f(r)= \frac{{-ke^ {-r/a}}}{r^2} $$ the adequate potential is $$ V(r)= \frac{{-ke^ {-r/a}}}{r} $$ I'm trying to understand why $$ -\frac{\...
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Spin, directions and measurement

The question I'm trying to answer is: does the spin of a particle have a fixed direction without measuring it? I understand that when I measure the spin of a particle using, say, a magnetic field, ...
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1answer
23 views

Gauge transformations of potentials with a step function

In have a question about the following exercise. I am given the following expressions for the scalar and vector potential, $$\vec{A}(\vec{r},t) = \frac{\sigma}{\epsilon_0}\left[\frac{x}{c}\hat{x} + tU(...
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Superposition scalar and vector potential and change Maxwell equations

I read some topic about the superposition of electric field and ... but do not mention about scalar and victor potential and superposition. I have a question If I have three electromagnetic fields ...
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1answer
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Energy of Ground State of Quantum Well

I struggle with the following concept. Consider the finite square well potential in the figure below. Consider the case where the electron energy is below the potential ($V(x) = V_0$) outside the ...
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How is potential difference greatest when battery is not in a circuit?

I was just studying physics and came across this in the textbook that “A cell produces its highest p.d. when not in a circuit and not supplying current.” Could you please explain this? If the cell is ...
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Electron volt to volt question

An $\rm{eV}$ (electron volt) is equal to a volt. So that volt it is equal to, is it based on 1 volt rms or one volt peak to peak or one volt average, or some other calculation of a volt?
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Velocity potential of an irrotational vortex

I would like to investigate the isolines of a two-dimensional velocity potential of an irrotational vortex defined using polar coordinates as $v=\frac{K}{r}$. I understand that the velocity ...
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1answer
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What is a 'potential' in the context of physics and gauge symmetry?

I heard someone say that the definition of a gauge transformation is any formal, systematic transformation of the potentials that leaves the fields invariant. What is the definition of a potential in ...
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3answers
63 views

Verify that the electrostatic potential satisfies the Poisson equation [closed]

I'm reading Sect1.7 of Jackson's classical electrodynamics but I have trouble following his argument. Could someone help explain how exactly the Laplacian is evaluated in 1.30? Is it calculated with ...
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1answer
39 views

Gravitational potential energy defined as the work done on a mass

Our physics sir made us write that gravitational potential energy is the work done in bringing a mass from infinity to a point without acceleration, but I am confused because if acceleration is $0$ it ...
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Conceptual electric potential question

The diagram below represents two metal spheres, and one of them is connected to the earth so is at $0 \; \text V$: The answer says that the charge of the earthed sphere is negative, and less than the ...
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Induced electric field inside an inductor [closed]

Okay so I was recently taught about inductors and how they generate an emf which opposes the increasing magnetic flux due to an increasing current. In an LR circuit, the current flows through the ...
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1answer
26 views

Energy conservation in motional emf

If a rod enters a region of uniform electric field, a potential difference arises between the ends of the rod. The work required to create this potential difference comes from the magnetic field. If ...
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1answer
44 views

Direction of current when there are 2+ batteries on circuit

By the conventional direction, current points from + to -. But what happens when there are more than one batteries on the circuit,with the battery poles connected to each other with any combination? ...
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Taylor expansion of retarded vector potential

I am currently trying to understand the Taylor expansion in radiation zone of the vector potential for a general time dependence. I know that the retarded potential is given by: $$\textbf{A}(\textbf{...
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Location of high and low potential points in motional emf

Okay so in the above image the semi circular loop is rotated and a sector of it is introduced into the magnetic field. Questions: I know the magnetic field is constant so no non conservative ...
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Why don't we define potential due to a magnetic field?

We define electric potential and gravitational potential and use them quite often to solve problems and explain stuff. But I have never encountered magnetic potential, neither during my study (I am a ...
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Aharonov Bohm effect [duplicate]

Not much about the underlying math, but how can an electromagnetic field exist when the electric and magnetic field is zero?
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Why does electric potential decrease across a resistor?

If electric potential energy is similar to gravitational potential energy, then shouldn't the potential drop as the charges come nearer to the positive terminal like gravitational potential energy ...
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1answer
60 views

How are charges redistributed on a system of parallel conducting plates? [closed]

I’ve seen quite a few questions where some charge is given to a conducting plate and we are to find the final charge on each face of the plate and on the faces of some nearby plates. While there have ...
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81 views

Why does field strength follow the inverse square law but potential does not?

Either in a gravitational or electrical field, let's say an electrical field, the electrical field strength follows the inverse square law. This is fairly intuitive just due to the geometry of the ...
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What does EMF actually mean?

After studying EMF in DC circuits I realised that EMF is just the potential difference between cell terminals in an open circuit. But then I was introduced to Faraday's laws of electromagnetic ...
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1answer
41 views

How is the electric potential at infinity zero in the “Isolated sphere” case of a spherical capacitor?

The following statement is from the book Concepts of Physics by Dr. H.C.Verma, from the chapter on "Capacitors", under the topic "Spherical Capacitor - Isolated sphere": If we assume that the ...
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A doubt in the derivation for determining the electric potential difference between concentric spherical shells

In Concepts of Physics by Dr. H.C.Verma, in the chapter on "Capacitors", in page 146, under the topic "Calculation of Capacitance" for a "Spherical Capacitor" the following is given which is a part of ...
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59 views

Electric voltage versus gravitational voltage across a unifom field

Let us say we have a uniform electric field, like between two charged plates separated by a distance $d$. The formula for the voltage between the plates is $\Delta V=Ed$. But what is the value of ...
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5answers
67 views

How does voltage drop in series connection happen?

The fact that the voltage is the same for two elements connected in parallel seems very clear and intuitive. But when switching to the other related idea, of voltage drop in series connection, I do ...
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1answer
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How to setup a voltage divider to provide a reduced voltage for a lamp

I am learning about voltage dividers. In simple words, a voltage divider is a specific circuit setup where we connect multiple passive elements in series, in order to divide the main voltage into ...
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Current, Potential difference and fixed resistor [closed]

So from my understanding V = IR, so I = V/R. Shouldn't the calculation for this problem be 9V / 20 Ohms? However, I do not see an answer for 0.45A. The answer is 0.3A. Am I reading the question ...
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Physical interpretation for wave function in infinite square well

If you look at the wave function of a particle in infinite square problem for some specific energy level, say for n =1, then the probability of particle to be found in middle of the well is higher ...
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Confusion in the sign of work done by electric field on a charged particle

In my book* it is given, "the work done to transport a charge $q$ through a potential difference $\Delta V$ is $q \Delta V$." Or mathematically, it can be written as follows:$$W_{\text{electric}}=q\...
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Does the electric potential depend on particle velocity?

The energy $E$ of a charged particle with rest mass $m$ and charge $q$, which moves with velocity $v$ in electrostatic field with scalar potential $F$ is $$E=\frac{mc^2}{\sqrt{1-\frac{v^2}{c^2}}}+qF$$ ...
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What is the term for neutral electric field density?

What is the word or way of referring to a neutral electrical potential. For example let's say you have a 10 cm sphere of electrically neutral mass that is 1 Kg mass and you separately have a different ...
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Charge on hollow spherical surface

Let a point charge $+Q$ is placed in center of hollow spherical conductor of inner radius $a$ and outer surface $b$. Then the charge on the inner surface of radius $a$ is $-Q$ and outermost surface ...
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If force depends on both position and time, how to find potential energy?

Suppose force on a particle depends on both position of the particle and time. In this case, how to find potential energy of the particle? To be specific, force is $$ F(r,t) = (k/r^2) \exp(-\alpha t)...
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Understanding a 1-dimensional QM bound state

My lecturer has prescribed some practice problems, including the following: Consider the potential $$V(x)= \begin{cases} \ + \infty & x<0 \\ -V_0 & 0<x<a\\ 0 & x&...
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How can a potential be non-central?

I'm studying nucleon-nucleon interactions and I'm reading that the potential for said interaction has a non-central (or tensor) component. Now, I understand that, when describing a 2-bodies problem, ...
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About the electric field inside a capacitor

If I have a metal sphere (a conductor) of radius $R$, carrying charge $Q_1$ with potential $V_1$, surrounded by a thick concentric metal shell (a conductor with inner radius $a$, outer radius $b$, as ...
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Is the E field generally conservative outside the cases when vector potential goes to zero?

In Ronald Wangsness' "Electromagnetic Fields" book, he states that $\textbf{E}$ generally depends on both a scalar and vector potential in the form, $$\textbf{E} = -{\bf \nabla}\Phi -\frac{\partial \...