Electrostatics is concerned with the electrical fields and scalar potentials of stationary electrical charges and charge distributions. Use this for questions about electromagnetic situations in which currents and magnetic fields are absent, otherwise use [tag:electromagnetism] and/or [tag:magnetic-...

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1answer
126 views

Induced charge due to charge distribution between two plates

I am trying to work through this problem: given two parallel square conducting plates (side w), one grounded(at x=0) and the other held at +V (at x=L where L < < w), and there is a charge ...
3
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1answer
137 views

Problem from Purcell and Morin's Electricity and Magnetism: Holding the charge in place

This is the problem given in Purcell and Morin's electricity and magnetism book. (Problem 3.2 If you have the book) Figure: I was able to figure out that the charges on A,B,C,D cant be held ...
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1answer
47 views

Equivalent DC circuit with charged conductors

I am trying to find equivalent circuit for a circuit composed of interconnected capacitors when isolated pieces of conductor may carry nonzero electric charge, and I have been struggling with this ...
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1answer
66 views

Self capacitance

I have two spheres of metal, each of radius $1m$, these spheres are effectively an infinite distance apart. I now connect a $1V$ power supply between these two spheres: (and wait an infinite amount ...
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0answers
13 views

Pearson correlation of neural responses with it's linear estimation

I am trying to anderstand the following fact: Suppose I have a linear estimation of a stimulus: $ \hat{s} = \mathbf{w}^T(\mathbf{r} - \mathbf{f}(s_0)) + s_0$ where $\mathbf{w}$ is a vector of ...
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1answer
113 views

What is the proof for Gauss's law? [duplicate]

What is the proof for Gauss's law? Can you give me some explanation and details with the proof?
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1answer
23 views

Maltese Cross Tube and the anode

I understand that Sir William Crookes' Maltese cross tube shows that cathode rays travel in a straight path but I am unsure of why the cathode rays aren't affected by the anode as there is an ...
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1answer
38 views

Why potential at infinity is 0? (sphere of constant electrostatic potential)

Suppose I have a sphere of radius $R$ with potential $V_o$. Since the volume inside the sphere is bounded, then the lack of curvature of the potential (i.e. $\nabla^2\phi = 0$) gives a potential $\phi(...
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2answers
50 views

Electric Potential of Point Charge (sign problem)

This question has been asked before, but the answers didn't clarify the problem for me, so I thought I might ask again. It's really a simple question. Let's say we're calculating the electric ...
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0answers
9 views

Discharge Static Electricity from Carpet without chemicals

I've got a large amount of static electricity built up in a room. Is there any way I could discharge the static without the use of chemicals?
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0answers
7 views

Why x-axis E field exist in Electroosmosis Example

The explanation in Wiki said it is because the surface charge will induce electrical double layer at top and bottom surface, so that if we apply x direction E field, there will be a flow between two ...
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2answers
76 views

How can the fact that there is no electric field inside a hollow conductor be explained by Faraday's ice pail experiment?

Basically something very similar to these pictures These are from two separate books. The bottom picture says that all the excess charge in an object can be transferred to an already charged metal ...
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2answers
37 views

Calculation of electric potential in Geiger-Müller tube [closed]

We are given a cylindrical rod with linear charge density $λ$, and a coaxial cylinder with linear charge density $-λ$, as shown in the picture. We are to show that the potential difference between ...
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1answer
36 views

Capacitance of Nested Spheres

Imagine that we have two nested spheres and I wish to calculate the capacitance. First of all, I'm able to do the calculation. What I'm confused about is how it is possible for the Electric Field to ...
2
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1answer
32 views

What are the clicking sounds when static electricity occurs?

Sometimes, when there's static electricity, soft clicking sounds can be heard. This may happen when two fabrics are rubbed or when you get a static shock. What exactly causes this sounds?
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2answers
53 views

Induced charges

Consider a charge +q placed inside a cavity of conducting body. Charges will be induced as shown in the diagram below. How do we show that the electric field at a point A inside the cavity due to the ...
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2answers
57 views

Equipotential surface paradox

Consider a point charge +q as shown below. Now consider a equipotential surface and two points in it A and B. now the potential at A is equal to potential at B. If we now integrate (E.ds) from A to B ...
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1answer
25 views

Dipole-dipole field

Assuming that we have two parallel and exactly identical electric dipoles. How does bringing them together change their frequency? What would such field look like (how would they interact)? In fact, ...
5
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2answers
164 views

Why resistivity of copper wire is not zero even at zero kelvin?

At zero kelvin, everything seems dead stop. There is no movement occurring at zero kelvin, even at atomic level. As there is no movement in atoms, there is no vibration of atoms about their mean ...
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3answers
44 views

What is the field near a sphere of charge, with opposite charge inside?

This is a question from my high school physics class years ago. I'm embarrassed to say I still don't understand the answer. Say we have a non-conducting (like garnet) spherical shell, with -1 C ...
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2answers
22 views

Electric fields and potential

E = electric field V = electrostatic potential r = distance ' = derivative E = - (V)' therefore if E increases V decreases Also if r increases E decreases ...
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2answers
68 views

What does the movement of charge in an object mean?

When it is said that charge "moves" throughout an object, like if negative charge moves to the edge of an object and the charges become polarized, does this mean that the electrons has moved to the ...
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0answers
128 views

Non-parallel plate capacitor's capacitance [closed]

So far, I fully understood how to find the capacitance of a parallel plate capacitor. However, for the case of non-parallel plate one, how one could solve that kind of problem knowing that one plate ...
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0answers
36 views

Why is there a potential well near a hydrogen nucleus?

A hydrogen nucleus consists of a proton and the electric potential is given by the formula KQ/r where Q is +1.6×10^-19. So plotting a function of electric potential with distance r should give a ...
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1answer
45 views

No change in voltage in a capacitor

While trying to solve this question: Photo copy of the question and answer: Question:On charging a parallel plate capacitor to potential V the spacing between the plates is halved and a dielectric ...
0
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1answer
25 views

Gauss Law - charges outside the gaussian surface

I have just learned Gauss Law and this question is bothering me: Suppose a cubic gaussian surface and a charge next to its right side (image below). According to Gauss Law, the electric flux over ...
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2answers
130 views

How much is a Coulomb, really?

I've heard it said in my physics class that a Coulomb "is a lot of charge". And I believe it; most of the problems I've done in the class so far involve charges on the order of micro-Coulombs (or, ...
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1answer
287 views

How to draw equipotential surfaces for a dipole or system of two like charges?

How can we draw the equipotential surfaces (i.e the surface which has constant potential on all its points) for an electric dipole and a system of two like charges? I read it in some book that they ...
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1answer
321 views

Electric Field within the cavity of a conducting sphere?

So the hypothetical situation that I am confused about is below: The situation consists of a point charge, +q, contained within the cavity of a spherical conductor of neutral charge. I understand ...
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0answers
13 views

Method of image charges (hemisphere on metal) (2) [duplicate]

This is a continuation from Method of image charges (semisphere on a metal) . nbubis helped me a great deal concerning this problem and in this post I want to address my problem with the computation ...
0
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0answers
20 views

Method of image charges (semisphere on a metal) (2)

This is a continuation from Method of image charges (semisphere on a metal) . nbubis helped me a great deal concerning this problem and in this post I want to address my problem with the computation ...
0
votes
2answers
97 views

A capacitor with a conductor between the plates [closed]

Consider a parallel plate capacitor of area $A$ with a distance between the plates $d$, disconnected from the battery. I wonder, how would the capacitance of the system change if we placed a conductor ...
3
votes
1answer
97 views

Method of image charges (semisphere on a metal)

I'm currently trying to study ahead for the upcoming semester since I'm on break and I'm stuck on the method of image charges. I've tried watching some youtube videos on that topic and I thought I ...
0
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2answers
560 views

Graph for Coulomb force vs $1/r^2$

We know that when there is a relation like x inversely proportional to y^2, the graph would be like this: But in this question"Plot a graph showing variation of Coulomb force(F) versus $1/r^2$, ...
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1answer
15 views

Electric charge due to a point

In my book its written,"Electric field due to a point charge is inversely proportional to 1/r square....This means that at all points on the spherical surface drawn around the point charge, the ...
0
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1answer
24 views

Electric charges and fields

After solving a few questions i have observed two things...Are they true?: When two identical metallic spheres, one uncharged and one charged with lets say +4Q are brought close to each other then ...
5
votes
2answers
2k views

Perpetual motion machine [duplicate]

I'm having trouble understanding why this machine doesn't work. Part of a ring, half of which is uniformly charged, is located between two oppositely charged plates, attracting to the negative one and ...
0
votes
1answer
49 views

Doubt in derivation of electric field at axial snd equatorial point

Firstly, in derivation of electric field at an axial point due to a dipole we have to determine the Electric field at a point P on the axial. So there are two electric fields acting on this Point P, E(...
36
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7answers
7k views

Why doesn't an electron ever hit (and stick on) a proton?

Imagine there is a proton confined in a box and we put an electron at 10 cm distance: It gets an acceleration of thousands of meters/second^2 along a straight line joining the two CM's. One would ...
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3answers
36 views

How does a conductor shield the outside from its inside

If I have a charge of +q placed arbitrarily within the spherical conducting shell, by Gauss' law, the E field produced will be created outside the shell, as if the charge were placed at the center. If ...
0
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0answers
80 views

Electric field at centre of two different hemispheres

I have a sphere separated into two hemispheres which are insulated from each other the bottom half is earthed and the top half has potential $V$. Radius=$a$. I am trying to find the Electric ...
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2answers
47 views

How paper strips get electrified?

Why paper strips get electrified when we iron them? I have learned that when two insulators are rubbed then they gets electrified but in case of ironing a paper the iron is a conductor. Will rubbing a ...
0
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1answer
30 views

What is the location of point charge with respect to the original charged body?

we say if distance between two charged bodies is large as compared to its size then we take them as point charges and assume all its charge content to be concentrated at one point in space. What is ...
0
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2answers
59 views

Electric Potential from separating charges [closed]

Say there are 2 charges, one of charge C, and the other with a charge of -2C. C=1.5*10^-6 C. Initially, they are right next to each other. I pull them apart to a distance of 15 cm. So I can use the ...
0
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2answers
61 views

Can a system be designed that uses no energy to accelerate particles to high velocity?

I have one system in mind. Although I know it is not possible to accelerate a particle to a higher speed without spending energy, I would like to know why the proposed system won't work. The system ...
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votes
1answer
60 views

What is the dielectric constant of a pure conductor?

Dielectric constant is the ratio of permittivity of a medium to the permittivity of free space. How to find dielectric constant of a conductor?
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1answer
57 views

Positions where the electric field is not defined

Can anybody help me to understand this statement given in my book? The electric field due to a discrete charge configuration is not defined at the locations of the discrete charges. For ...
0
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1answer
23 views

Charge in capacitor after switching voltage

Say you have a capacitor connected to a voltage source (vs). After the capacitor has fully charged, you cut the source voltage in half to vs/2. The voltage across the capacitor should change to match ...
0
votes
1answer
51 views

How to determine the cylindrical gaussian surfaces position while finding the electric field?

Today I encountered a question that had the solution: electric field outside of a charged nonconductor is $$ E=\frac{\sigma}{2\epsilon_0} $$ which had the diagram below: Fig. 1 and for the ...
0
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2answers
27 views

Direction of motion of particle when placed on line of force

An electric line of force in the $x-y$ plane is given by equation $x^2+y^2=1$. A particle with unit positive charge, initially at rest at the point x=1,y=0 will move along the circular line of force. ...