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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Conductance Charged Box

A box with thick and conductive sides with dimensions: Lx, Ly, Lz- while LZ>>Lx,Ly. The long dimension of the box [Lz] can be viewed as infinite so Phi(x,y,z)=Phi(x,y) Given that: Phi(0,y)=-Phi(Lx,...
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82 views

How do you derive a wave function?

I know this may be a dumb question to ask, but I'm a middle school student studying quantum physics out of interest and want to know how to find the wave function. Preferably in a square well.
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2answers
180 views

Electrostatics - Potential near conductor using Kelvins method of image charge

As the figure shows, I have a 2D image of a conductor seen from the front. It is located a height, h1, above a grounded plane of infinite area. The conductor has a voltage, Vc, as shown. Around the ...
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1answer
170 views

Converting from magnetic scalar potential to magnetic vector potential

Suppose that I have a situation where I can use the magnetic scalar potential. Given the magnetic scalar potential, is there a simple way to calculate the magnetic vector potential from the magnetic ...
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47 views

Fixing the potential for a quantum particle

I have started studying quantum mechanics and have realised that we can solve the Schrodinger equation for a particle's wave function if we know it's potential energy function. But the potential field ...
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125 views

Curl of gradient of potential in electrostatic

We know, curl of E is zero (this field is conservative). Again E=-grad V. So, we get curl of (-grad V)=0, i.e. curl of gradient of potential is zero. Is there any condition on potential?
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Calculating vector potential inside a Cylindrical shell carrying surface current in z direction [on hold]

I am trying to calculate the vector potential inside a cylindrical shell that carries constant surface current in the z-direction. We know that the field inside the cylinder is zero so I can't use, $$...
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20 views

Pretension cable - Minimum Potential Energy Formulation [closed]

If there is a geometry with pretension in an unstable state, like two cables with a predefined tension $T$ as seen in the figure. Due to a current geometry (which is not in equilibrium), there is an ...
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1answer
33 views

Electric potential / infinity is not the 0 reference

Let's say we have a charged sphere with radius $r$. Usually, the way we define its potential is $V = kQ/r$. In this way, we have defined its potential with infinity as the zero reference point. Let's ...
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1answer
101 views

Is there something wrong in my book's derivation of work done on charge?

For finding potential at a point due to a +ve charge $(q)$, we find work done to move a unit +ve charge $(q_o)$ from infinity to that point in the presence of +ve charge $(q)$ Since both charges ...
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2answers
310 views

Vector potential of a solenoid in the Coulomb gauge

I understand the usual argument for calculating the vector potential outside of a solenoid of radius $R$ with $n$ turns per unit length carrying current $I_0$ using $$ \oint \mathbf{A} \cdot d \mathbf{...
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1answer
51 views

Finite potential well; finding the energy “in a limit”

I've come a across the following variant of the finite-potential-well-problem in quantum mechanics: The potential is given by $V(x)=0$ for $|x| \geq a/2$ and $V(x)=-V_0/a$ for $-a/2<x<a/2$ where ...
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215 views

Barrier Potential for bound states

I'm having this problem for a while, but I'm still failing to realize what really is bothering me in this, so here is my attempt on explaining my doubt: I have the time-independent Schrodinger ...
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1answer
25 views

Is magnetic potential vector due to the magnetic field or energy stored in magnetic field?

My doubt is whether the magnetic vector potential is due to the potential energy stored in magnetic field or due to the magnetic field. Also I have another doubt. Since in electrostatics potential ...
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26 views

Resistors equivalent using symmetry and equipotential line

I propose the following statement: In a circuit, while determining equivalent resistance across two points, if the circuit is symmetric wrt the line joining the two points , we may fold the circuit ...
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2answers
183 views

Trying to understand the electric potential and potential energy

I am trying to understand some facts on electrical potential and potential energy. It is quite confusing in the text to say that the zero potential could be freely chosen for convenience. In that case,...
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1answer
809 views

Potential difference between two electrodes in an electrochemical cell

In an electrochemical cell, let's say you have a zinc and zinc ion half-cell as well as a copper and copper ion half-cell: The zinc electrode (or anode) dissolves into zinc ions while the copper ions ...
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2answers
128 views

Is the scalar magnetic potential continuos?

If we have two current-free spaces and separated by a surface current, we can solve the magnetic problem by solving two magnetic scalar potentials and then using matching conditions. My question is, ...
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3answers
117 views

Direction of $d\mathbf{l}$

A solid sphere has charge $q$ and radius $R$. Find the potential at a point a distance $r$ from the center of the sphere where $r>R$, using infinity as the reference point. My attempt: From Gauss'...
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1answer
22 views

Laplace equation outside sphere

When solving the Laplace equation on sphere coordinates you get: $$ u(r,\theta) = \sum_{n=0}^{\infty}\left( A_n\,r^n + \frac{B_n}{r^{n+1}} \right) P_n(\cos\theta) $$ And it is clear that if you have ...
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2answers
38 views

Electric potential in circuits

From what I understand from my notes, an e.m.f or electromotive force provided by a battery is the electrical energy per unit charge converted from other forms of energy required to drive a unit ...
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3answers
40 views

Electric Potential in the Center of a Electric Dipole

I thought the electric potential at point B would be positive because placing a positive charge at point B would cause it to move releasing energy while doing so. The answer key states that the ...
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20 views

What is the electric field between two coaxial conducting cylinders when a charged sphere is placed within the inner cylinder?

A long cylindrical capacitor of length $l$ consists of an outer conductor of radius $a$ and an inner conductor of radius $b$, where $l>>a$. The outer conductor is earthed, and the inner ...
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4answers
2k views

Can EMF be lesser than terminal potential difference?

Can terminal potential difference be greater than EMF? If so, how? Upto my knowledge and my research, during charging it can happen but the question remains same: how it happens. What is the basic ...
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23 views

Electric potential due to a current source - Basic equations

In my book I found the folowing formula of the electric potential generated by a current source: $$ \Phi = \frac{I}{4 \pi \sigma} \frac{1}{r} $$ where I is the current, $\sigma$ the electrical ...
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2answers
22 views

Ideal/Non ideal Voltmeter across a battery with no current flowing

If I consider a voltmeter and connect it across a battery , which is in such a circuit , that no current is flowing in that branch (Before Voltmeter is connected), will the voltmeter, show the EMF of ...
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3answers
103 views

Understanding bound states in quantum mechanics

Suppose I have this potential: $$ \ V(x)= \left\{ \begin{array}{ll} +\infty & x < 0 \\ -V_0 & 0\leq x\leq a\\ 0 & x>a \\ \end{array} \right. \ $$ for $a>0$...
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2answers
28 views

Equipotentiality of the conductor surface with extra charges sprinkled and Poisson's equation

The electrostatic potential $\phi(x,y,z)$ everywhere on the surface of a conductor/metal is the same. For a quick reference see this post. Hence, any derivative of $\phi(x,y,z)$ must be zero on the ...
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1answer
33 views

Clarification on electric potential energy

From what I understand from my notes (correct me if I'm wrong), electric potential energy is the work done in bringing the charge from infinity to a certain point from the source charge. Let this ...
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7answers
414 views

Why electric potential requires absence of acceleration?

As of 28/05/2019, Electric Potential is defined in Wikipedia in the article with the same name as: The amount of work needed to move a unit of positive charge from a reference point to a specific ...
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1answer
195 views

Form of the one-pion exchange potential

Part of the one pion exchange potential (OPEP) contains the following term $$V(r) \propto (\vec{\sigma}^{(1)} . \nabla)(\vec{\sigma}^{(2)} . \nabla) \frac{\exp\left(- \frac{r}{R}\right)}{r} $$ And I ...
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1answer
124 views

Deriving energy eigenfunctions of Infinite square well with nonzero bound

I've been asked to derive the eigenfunctions for the infinite square well, but by using boundaries of $L/2$ and $-L/2$ instead of $0$ and $L$ I'm happy with the general solution found using the TISE ...
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2answers
129 views

Potential difference in a nonuniform electric field

Let's say I have two points in a nonuniform electric field and those points have the electric potential 10 V and 5 V. If I then would use a voltmeter to determine the voltage between those points ...
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1answer
70 views

How to take the derivative of potential?

The electric potential $\psi$ at a point inside the volume charge distribution is: $$\displaystyle \psi = \lim\limits_{\delta \to 0} \int_{V'-\delta} \rho'\ \dfrac{1}{|\mathbf{r}-\mathbf{r'}|} dV'.$$ ...
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1answer
18 views

Taking into consideration the non-0 value of an equipotential in a method of images problem

If the infinite conducting plane in the diagram above is grounded, then $V=0$ on the plane and the image problem is easy to solve - just put the dotted $-q$ charge there and the $V=0$ equipotential ...
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3answers
63 views

How can you use the potential to find the electric field? [closed]

Lets say we have the above system of point charges. We were asked to find the electric field at the centre. Superposition of electric fields gives the right answer, but how can we do it by ...
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4k views

What is the equation of the gravitational potential in general relativity?

How is the gravitational potential replaced by the metric tensor in general relativity? $$U_G=\frac {GMm}{r}$$ What is its equation?
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97 views

Even and odd solutions to time independent Schrodinger equation on symmetric potential

I have to solve the following problem: Consider the potential well: $$ V(x)=-V_0, \hspace{10px} |x|<a/2 $$ and $0$ everywhere else. $a$ is also a positive constant and so is $V_0$. Find the ...
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1answer
39 views

Is electric potential just the sum or measure of Electric Potential Energy for a given unit of matter with electric change?

I understand Electric Potential as follows (I "synthesized" the definition from different definitions I found online): The sum of Electric Potential Energy for a matter particle with an electric ...
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5answers
5k views

Why is $E=-dV/dx$?

I know Work= minus Electric Potential Energy. So you have: -qdV=-qE dx and thus E= minus dV/dx. But does that 'minus' sign have any effect so E vector's direction. Say we have the fields lines (red)...
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1answer
55 views

Why does a voltaic cell induce an electric force proportional to voltage?

I'm trying to understand the intuition behind Ohm's law (that current is proportional to voltage). I understand the basics of the Drude model: if the electrons frequently collide and on average reset ...
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1answer
257 views

Understanding Charge Density when using Laplace's Equation

I'm following Griffith's Intro to Electrodynamics, and when discussing Laplace's Equation, it states Very often we are interested in finding the potential in a region where $\rho = 0$. So, if you ...
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1answer
50 views

Showing $ \nabla \cdot \mathbf A = 0$ using integral formula

In Coulomb gauge the vector potential is chosen so that $ \nabla \cdot \mathbf A = 0$ and we find $$ \nabla^2 \mathbf{A}=-\mu_0 \mathbf j $$ The solution to which is $$ \mathbf A(r) = \frac{\mu_0}{4\...
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3answers
72 views

Is a complete circuit required for capacitors to redistribute charges?

Suppose I have two capacitors of different capacitance $C_1$, $C_2$and they have been charged prior connecting by voltage of $V_1$ and $V_2$ respectively the positive plate of one capacitor is ...
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0answers
26 views

Connecting one lead of capacitor to a certain charged object (to get a potential difference)

Setup-A charged sphere , connected to one plate of capacitor , other lead of capacitor is free. Question-Will the capacitor plates go through a charge redistribution ? Arguments/Counterarguments-I ...
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1answer
31 views

Work done in moving a charge in circuit?

Why is the work done in moving a charge from one point to another in a circuit through any path the same even though heat and other losses are there?
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162 views

How one can use the Klein-Gordon equation to deal with the hydrogen atom? [closed]

I'm not familiar with physics jargons compare to those who study physics professionally, but to remark my knowledge regarding this question, the Klein-Gordon equation is a relativisitc equation for ...
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1answer
44 views

How do you measure voltage from first principles? [closed]

I've always wondered if you were thrown back in time with just my cell phone, how could I charge it... I know how to make electricity, but how do I check the voltage if all I have access to is, shall ...
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2answers
57 views

Work done by battery?

Why the work done by a battery is Q*V where V is emf of battery and Q is charge that is made to flow in circuit?please explain detail? explain and write the formulas
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2answers
41 views

Why the electric field on the surface of charged spherical shell of radius $R$ and charge $q$ is $\frac{kq}{R^2}$?

As we know the electric field at a point due to charge $q$ is equal to $\frac{kq}{r^2}$ where $k$ is the constant of proportionality and $r$ is the distance between the charge and the point (where we ...