1
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1answer
29 views

Help regarding understanding derivation of electrostatic potential in a solution to a problem

I was looking at the solution of finding the energy stored in a charged solid sphere in which the electric field was and then later stated the electrostatic potential is I understand that to ...
2
votes
3answers
85 views

How come we talk about gravitational potential energy and not gravitational potential?

With regards to gravity the equation learned is $$U=-\frac{GMm}{r}$$ And the relationship to force is $$F=-\frac{dU}{dr}$$ In electrostatics we instead talk about electric field and electric ...
1
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1answer
18 views

Electrohydrodynamics: How will electric potential develop in a fluid when potential is applied from ends

Lets say, I have a fluid in a rectangular enclosure (2D). I apply electric potential $U=U_1$ at left boundary and $U_2$ at right boundary. In the lower and upper boundaries, the potential varies ...
0
votes
1answer
13 views

How is electric field strength related to potential difference?

I was looking at the derivation of drift velocity of free electrons in a conductor in terms of relaxation time of electrons. Here a metallic conductor XY of length $\ell$ is considered and having ...
3
votes
1answer
49 views

Why is electric potential positive?

If there is a positive charge $q$ at the origin of a coordinate system, the electric potential $\phi$ at a distance $r$ from $q$ is (by definition, if we take the point of zero potential at infinity): ...
2
votes
1answer
52 views

Potential energy of a dipole in a uniform electric field convention?

When finding the potential energy of a dipole in a uniform electric field, I was told by my lecturer that the convention is that the potential energy is 0 when the dipole moment and electric field ...
2
votes
3answers
219 views

When to use method of images in Electrostatics?

I am a bit confused about when to use the method of images in E&M? For example, in Griffith's Electrodynamics Example 3.2, the problem reads: A point charge $q$ is situated a distance $a$ from ...
3
votes
3answers
176 views

How to solve the Laplace Equation in the hollow square region?

Suppose the values of $a$, $b$, $V_1$ and $V_2$ is given. I want to find the solution of the Laplace equation, $$\frac{\partial^2 \phi}{\partial x^2}+\frac{\partial^2 \phi}{\partial y^2}=0$$ in the ...
1
vote
0answers
21 views

Surface potential resulting from the charge transfer between insulator and conductor

Common non-contact electrostatic voltmeters are used to measure the surface potential. Imagine we place a charged insulator on top of the conducting plate (insulated from the surrounding) and measure ...
0
votes
0answers
40 views

Variation of Electrostatic Potential with Distance in a Uniform Field

I came across this question in a problem book: If a proton is released from rest in a uniform electric field, does the electric potential at those points where the electron moves increase or decrease. ...
1
vote
0answers
38 views

Potential generated by a hollow sphere with a hole

The sphere has radius $R$ and is missing its "pole" - meaning that in the area $\theta\leq\alpha$ there is nothing. The object has a homogenous charge density $\sigma=\frac{Q}{\pi R^2}$ I'm trying to ...
2
votes
2answers
83 views

Meaning of “Grounded”

In my opinion, "grounded" means having the same potential as the potential at infinity, which is usually set to zero. Now if we consider a conductor inside a uniform electric field, what is the ...
0
votes
2answers
109 views

Grounded conductor inside a uniform electric field [duplicate]

I am working on a textbook problem of a grounded conductor inside a uniform electric field. The textbook states that "grounded" means potential = 0. In my opinion, "grounded" should mean "same ...
1
vote
1answer
64 views

Integration over $S^2$ in electrostatics

I'm studying for a test in electrostatics and I'm always failing on putting up the correct integrals. In one problem I have the surface of a sphere with radius $a$ and an opening angle of $2\theta$. ...
1
vote
1answer
93 views

Find the points where potential is null

Let's say we have two charges called $q_1$ and $q_2$, respectively $20 \, C$ and $-40\,C$, at a distance $d=1\,m$ We want to find all the points where electric potential is null. I solved the ...
0
votes
0answers
50 views

Electric Potential Change

Imagine we have a conductor in the shape of a sphere with charge $Q$ on it. The conductor is not grounded. There is an associated potential $V=\frac{Q}{4\pi\epsilon_0 R}$ at and in the sphere, where ...
0
votes
1answer
74 views

What is the correct way to take out equivalent capacitance here?

So here I have a capacitor with two plates , one positively charged and one negatively, as shown in the figure. Now the material between them is $k_1$ for thickness d/2 and $k_2$ for the other d/2. ...
0
votes
1answer
52 views

Calculating electric potential from a changing electric field

Assuming that I calculated the electric field in a single point between a uniform charged positive sphere and an infinite long wire charged positive uniformly. Now, I want to calculate the velocity of ...
2
votes
1answer
80 views

A zero gravitational potential and non zero gravitational field

Give an example of a situation in which there is a non-zero gravitational field and a zero gravitational potential at the same point? $$dV=-\vec E\cdot d\vec r.$$ The above equation implies that ...
1
vote
1answer
89 views

Clarification of multipole expansion for a point charge

In Griffith's electrodynamic: 3.4.2 He pointed out that the monopole term is the exact potential for a single point charge. However I was under the impression that different configuration of a ...
2
votes
1answer
159 views

An Electric Potential Glued to a Cube-Shaped Insulator to Replicate a Point Charge: Charge Distribution

I have been going back over this problem with a friend for the better part of a day: A potential is glued to a cube-shaped insulator so that outside of the insulator the field is the same as a point ...
1
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3answers
158 views

How can the potential on a cube's surface replicate the potential of a point particle?

If i have a cube (either hollow, or an insulating solid) and i want its surface have a potential such that it looks like a point particle outside of the box does that mean the exact potential on the ...
4
votes
2answers
132 views

Argument for symmetry of potential

Consider the following electrostatic charge configuration of a spherically symmetric, perfect conductor with total charge $Q = 2q$, where $q > 0$. A point charge $q$ is placed at the position ...
2
votes
3answers
118 views

Calculating the Potential from the E-Field

I find that often times I'll be tripped up by questioning whether or not I can do something mathematically, and be unable to come up with a satisfying answer. This is, unfortunately, one of those ...
-1
votes
1answer
66 views

Electric Potential Energy

When work is done on a positive test charge by an external force to move it from one location to another, does the potential energy increases or decreases, and does the electric potential increases or ...
0
votes
1answer
99 views

Question related to Equipotential Surface

How will you show that equipotential surface is always directed perpendicular to electric field?
3
votes
1answer
78 views

Intuitive explanation of difference in $r$-dependence between dipole and monopole

For an electric monopole, its potential scales with $\frac{1}{r}$, where $r$ is the distance from the point of interest to the charge. However, for a dipole, its potential scales with $\frac{1}{r^2}$. ...
1
vote
4answers
264 views

Electric potential and maximum charge on a conductor

Does increasing the amount of electric charge on a conductor cause an increase in its electric potential to a point at which it becomes maximum; where it can hold no more extra charge? Is it true? ...
5
votes
1answer
121 views

Is there any good reason/argument/heuristic why one can approximate forces by approximating the potentials?

My question Is there any good reason/argument/heuristic why one can approximate forces by approximating the potentials? (As a concrete example, in Electrostatics.) Motivation for the question I am ...
0
votes
1answer
138 views

Electrical potential difference?

What is the electrical potential difference and why we have to talk about a difference and not about the electrical potential itself? What is the electrical potential difference in practical terms ...
4
votes
1answer
128 views

How do aspherical gravitational monopoles look like?

I was recently pointed by laboussoleestmonpays to a beautiful paper from some time ago, Aspherical gravitational monopoles. Alain Connes, Thibault Damour and Pierre Fayet. Nucl. Phys. B 490 no. ...
-4
votes
2answers
296 views

Alternative derivation for the capacitor energy equation [closed]

I hope this is the right place for this kind of post. A friend is trying to derive the equation for the energy stored in a capacitor by analysing the change in potential on one plate when the ...
-2
votes
2answers
51 views

Finding out the potential [closed]

According to me, if we want to find out the potential the the equation will be, $$dV = \int \frac{dQ}{4 \pi \epsilon_0 x}$$. But the answer is given is on the basis of $$dV = \int \frac{dQ}{4 ...
2
votes
1answer
101 views

Slight variation to method of images

Suppose a point charge $q$ is located at $(x=0,y=0,z=d)$, and that along the $x$-$y$ plane is a infinite plate of potential $V = 0$. Then the method of images solves Laplace's equation for the ...
2
votes
2answers
3k views

Why does the electric field perpendicular to every point on the surface of a conductor?

I am reading Berkeley Physics Course, Volume 2 (Electricity and Magnetism by Edward M. Purcell). I am in chapter $3$ pg $92$, and the book discusses conductors. The following is from the book: ...
1
vote
3answers
4k views

Why is Energy = Voltage x Charge, and how to prove that?

As you know the equation $\mathbf{E=V\times Q}$. Where: $\mathbf E$ is the energy measured in joules, $\mathbf V$ is potential difference (Voltage), $\mathbf Q$ is the charge. So my qustion is: ...
3
votes
2answers
488 views

Potential of arbitrary charge distribution

Imagine this: You have a sphere of air where you have no charge and around this sphere you have a charge distribution $\rho(r,\theta,\phi)$. (For instance, this could be ...
3
votes
1answer
242 views

Frank-Hertz experiment setup

The usual schematic representing the setup of Frank-Hertz experiment is the following: However, sometimes, you can see a bit different schematic: My question is: what function does $V_{G_1K}$ ...
1
vote
1answer
2k views

How to find electric scalar potential of infinite wire with Poisson/Laplace equation?

I though it will be easier then calculating the electric field and then integrating, but I am stuck. lets say we have an infinite wire, charged $\lambda$ per unit of length and its located at the ...
1
vote
2answers
175 views

How charge distribution takes place when a battery is connected to a conductor?

When one terminal of a battery say of 1.5 volt connected to a short length wire, few electrons get transferred from battery terminal to the wire raising the potential of the wire also to 1.5 volt. We ...
1
vote
6answers
1k views

Electrostatic Potential Energy Derivation

How is the boxed step , physically as well as mathematically justified and correct ? Source:Wiki http://en.wikipedia.org/wiki/Electric_potential_energy As work done = $- \Delta U $. for Conservative ...
2
votes
2answers
339 views

Electrostatic Potential Definition

In the book, Introduction to electrodynamics by David J. Griffiths, he introduces potential separately as a function and potential energy through that function. How can potential be defined before ...
0
votes
1answer
78 views

Potential of a Body

I have a doubt about the electric potential of a body. Well, I know that given a continuous distribution of charge we can find the potential at a point $a$ using the following relation: ...
1
vote
1answer
212 views

How to find Electrostatic Potential Difference?

I have a really simple doubt about finding the potential difference in electrostatics. Well, first of all, the definition of potential difference is very clear to me: we take a path between the points ...
0
votes
1answer
200 views

Potential of a conductor depends on the size and shape of the conductor. How?

1) When a charge 'q' is given to an isolated conductor, its potential will change. 2) The change in potential depends on the size and shape of the conductor. I could understand the point no. 1. ...
1
vote
5answers
4k views

Workdone in an equipotential surface is zero?

An equipotential surface is one in which all the points are at the same electric potential. If a charge is to be moved between any two points (say from point A to point B) on an equipotential surface, ...
0
votes
1answer
360 views

Non conducting charged planes

I have two parallel non conducting charged planes with opposite charges $6\mu C/m^2$, area $A = 3m^2$ and distance between the planes $d = 0.004 m$. I know the potential between these two planes is ...
0
votes
1answer
76 views

Electric charge and the distance

The strength of an electric field is: $E = 200\ \mathrm{N/C}$ The potential (of the test charge) is: $V = 600\ \mathrm{V}$ $\epsilon_r=1$ I need to calculate the distance between this point and the ...
2
votes
3answers
672 views

Potential Inside Conducting Cube

A cubical box with sides of length L consists of six metal plates. Five sides of the box { the plates at $x=0, x=L, y=0, y=L, z=0$ - are grounded. The top of the box (at z = L) is made of a separate ...
2
votes
1answer
2k views

Gradient of the electric potential

I was wondering if for a point-like charged object, does the gradient of the electric potential point in the direction of maximum increase or maximum decrease of the function $V$?