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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Electric Field of a Disk an Infinite Distance Away

The electric field of radius $R$ and a uniform positive surface charge density $\sigma$ at a distance $x$ from its center is given as $$E = \frac{\sigma}{2 \epsilon_0}\left( 1 - \frac{1}{\left(\frac{...
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2answers
27 views

Torque on electric dipole placed in non uniform electric field

When electric dipole placed in non uniform electric field, what is the approach to calculate torque acting on it? Can it be zero?
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Charge density on two hemispheres, enclosing a conducting sphere

Two uniformly charged non conducting hemispherical shells each having uniform charge density $\sigma$ and radius $R$ form a complete sphere (not stuck together) and surround a concentric spherical ...
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13 views

triboelectric effect at a liquid-liquid boundary?

In reading up on the triboelectric effect, most experiments deal with solid-solid interfaces. I've found some studies regarding solid-liquid boundaries, and even some engineering manuals outlining the ...
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44 views

Why do we integrate in the following derivation? [on hold]

Electric potential due to a point charge. Let a point O have charge $q$ at a distance $x$ from point A and at a distance $r$ from point P ($r<x$). Suppose a test charge $q_1$ is placed at A force ...
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36 views

Weight of sphere in kerosene [on hold]

Two identically charged spheres are suspended by strings of equal length. When they immersed in kerosene, the angle between their string remains the same as it was in the air. Find the density of the ...
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40 views

What one would observe on extremely high voltages?

I am interested which physical processes generate the highest electrical voltage and what the highest measured voltage is. In everyday life, electrostatic charges e.g. while walking with socks on a ...
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1answer
33 views

Derivation of dipole moment of array of point charges

This question is about the equation describing the net dipole moment for an arbitrary number of point charges. Here's what I understand: For two point charges $q$ and $-q$ with positions $\mathbf{...
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1answer
37 views

Poisson's equation with point source

PDE's are not my thing, but I'm trying to calculate the voltage in a finite conducting sphere, based on a point current source. With Poisson's equation of $\nabla^2\Phi = -\frac{J}{\sigma}$, where $J$...
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40 views

Total chemical potential of electrons in pn junction

I am reading this page about electron energy concept terminology. I am trying to apply that for the pn junction in equilibrium below. Could anyone help me to see if I get it correctly? C = ...
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30 views

Potential difference between a solid sphere and a shell [on hold]

A solid conducting sphere having a charge $Q$ is surrounded by an uncharged concentric conducting spherical shell. The potential difference between the surface of solid sphere and the shell is $V$. ...
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41 views

Is it true that it is a misconception that the Van de Graaf generator works with the Faraday's ice pail principle

I found some interesting papers which claim that it is a misconception that the charge accumulation on the top is due to the Faraday's ice pail principle but rather just as in Volta's condensing ...
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Simple Van de Graaff generator with friction only

I have found an interesting picture about different versions of the Van de Graaff generator: (Source: http://www.coe.ufrj.br/~acmq/vdgself.jpg) I know the Wimshurst system on the right but I have ...
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How is charge distributed in the given parallel plate system? [on hold]

The 2nd plate has been given a charge Q, and the 1 & 4 plates are connected by a wire. How is the charge distributed among the different faces of the plates?
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1answer
30 views

main cause of self charging of unshorted capacitors?

In the lab, we keep all of the high voltage capacitors shorted when not in use, and rightfully so. They tend to spontaneously charge when left for some time and become extremely dangerous. while the ...
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1answer
11 views

How do ink droplets passing through two charged metal plates become charged as well?

In the working mechanism of an inkjet printer, I came to know that ink droplets in the form of a stream pass through two charged parallel metal plates ( like a parallel plate capacitor) and while ...
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2answers
35 views

Electric field of uniformly charged plane

Which are the null components (in a Cartesian coordinate system) of the Electric field of uniformly charged plane in $x=0$? I consider the coordinates : $(x,y,z)$ I think that $E_x = 0$, $E_y \ne 0$, ...
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2answers
55 views

Energy of electric field and magnetic field

I am studying about inductors and capacitors. They store their energy in the form of electric field and magnetic field.Energy is required to create fields.But if we take an isolated charge and nothing ...
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3answers
32 views

Dipole Moment and separation

My understanding of a dipole moment is it defines the strength of various dipole interactions, eg the common example of torque in an electric field. My confusion stems from the fact that the magnitude ...
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125 views
+100

Electric Potential Field of Parallel Electrodes within Grounded Shell

Any help would be greatly appreciated I think I need to solve this using boundary potential conditions and Laplace equations. Here is the system I'm attempting to model: The red rods are metal ...
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0answers
26 views

wave equation in dielectric medium [closed]

Maxwell's equations: $$\nabla \cdot \mathbf{E} = \frac {\rho} {\epsilon}$$ $$\nabla \times \mathbf{E} = - \frac {\partial \mathbf{B}} {\partial t}$$ $$\nabla\cdot \mathbf{B} = 0$$ $$\nabla \times \...
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33 views

Suppose that the electric force were independent of distance, how would electrostatics be studied? [closed]

The electric force between two charged particles becomes weaker with increasing distance. Suppose instead that the electric force were independent of distance. In this case, would a charged comb ...
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11 views

How will charging by induction, friction and contact help in this situation? [closed]

Two metal spheres are hanging from nylon threads. When you bring the spheres close to each other, they tend to attract. Based on this information alone, discuss all the possible ways that the spheres ...
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How are the charges In this situation transferred [closed]

If you peel two strips of transparent tape off the same roll and immediately let them hang near each other, they will repel each other. If you then stick the sticky side of one to the shiny side of ...
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1answer
25 views

What does negative potential at a point signifies?

I am am bit confused in the concept of electric potential. Does this means there is a decrease in the potential energy. Suppose a point has( - 40V) potential, does this means that the place from ...
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1answer
34 views

What are dimensions of co-ordinates which are used to define an electric field?

A possible electrostatic field is: $ E_x = 6xy$ $ E_y = 3x^2-3y^2$ $ E_z = 0$ Suppose we are using SI system. So unit for components of field is volts/meter. Then what are dimensions of $x$ and $...
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Electric potential due to surface charge distribution on a conducting sphere

Let's consider a conducting sphere. If we charge the sphere, it is understood that there will form a surface charge distribution such that the surface of the sphere is an equipotential surface $ 0=\...
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3answers
85 views

Why doesn't $E$ depend on $x$?

Suppose that in $\mathbb{R}^3$ the infinite yz-plane is charged with a superficial charge density of $\sigma$. Then I have calculated that the electric field is equal to $E=sgn(x)\frac{\sigma}{2\...
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1answer
18 views

Force between plates of a capacitor with dielectric a battery

My teacher told me that the force will increase $k^2$ times, where $k$ is the dielectric constant, but I don't see how. To start with, with no dielectric, the force between the plates is given by $\...
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1answer
64 views

Why does the divergence of the Ponyting vector have energy flux density?

The poynting vector is defined as $\vec{S}=\mu_{0}^{-1}\vec{E}\times \vec{B}$ Taking the divergence of the poynting vector, one arrives at $\vec{\nabla} \cdot \vec{S}=-\frac{\partial u}{\...
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1answer
40 views

Why metal sphere (conductor) is used in Van de graff as the output terminal, not any other material , specifically any insulator?

Why metal sphere (conductor) is used in Van De Graff as the output terminal, not any other material, specifically any insulator?
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2answers
119 views

If a water molecule is neutral how do water molecules attract one another by electric force & form water?

This no sense to me! (im new to physics) and my textbook didnt explain this well!
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Electric Field Due to 4 cavities inside a sphere?

I found an interesting question and performed a calculation regarding field inside a cavity inside a spere which has four more cavities ? Is my calculation correct ?
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1answer
78 views

Proof of integral form of Gauss's Law from Coulomb's law without using differential form of Gauss's Law

The integral form of Gauss's Law is: $$\unicode{x222F}{\vec{E}}\cdot{\vec{dS}}=\dfrac{q}{\epsilon_0}.$$ Is there a direct derivation of it from Coulomb's law without using differential form of Gauss'...
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43 views

Uniformly charged rod electric field

A uniformly charged rod of length $L$ and total charge $Q$ lies along the $x$ axis as shown in in the figure. (Use the following as necessary: $Q$, $L$, $d$, and $k_e$.) (a) Find the components of ...
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0answers
37 views

Field inside a dielectric spherical shell

I would like to find a detailed solution for the internal electric field of a polarized dielectric spherical shell in a uniform applied field.
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1answer
25 views

Electrical gradient

I'm a zoology minor and I'm trying to understand electrical gradient. I found this explanation in an authentic website but cannot undertand it fully. An unequal distribution of charges across the ...
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2answers
42 views

Electric Field and Force from four particles

Four charged particles are arranged in a square as shown below, with A=3, B=4, and C=5 (a) Determine the electric field at the location of charge q. (Use the following as necessary: $q$, $a$, and $...
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17 views

Boundary conditions while finding electric potential inside some specific volume

Please see the figure. Continuous charge distributions are in blue color. Inside cavity there is some charge distribution. Also On surfaces S1 and S2 there are some charge distributions (not shown)....
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Maxwells equations at a point

Why is it that whenever a problem is posed for maxwells equations -say the electric field at some area- that it is only requested for a fixed/given point? It would seem like you would want the field ...
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2answers
24 views

Potential difference between two assymetrically charged plates

What is the potential diff between two plates of charges $q_1$ and $q_2$ ($q_1$ $>$ $q_2$)? I know the equation is $V = \frac{q_1-q_2}{2C}$ where $C$ is the capacitance of the system but how has ...
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2answers
29 views

Surface charge outside conductor

If I have a hollow conductor of arbitrary shape, and have a charge placed inside is cavity, then is there anything I can say for sure about the charge distribution on the outer surface? I know that ...
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1answer
19 views

Electrostatic pressure

https://en.wikipedia.org/wiki/Electrostatics says that "This pressure tends to draw the conductor into the field, regardless of the sign of the surface charge." Does this mean that if I place a ...
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3answers
78 views

when current passes through a wire , does it only travel through the outer surface?

In electrostatics we are taught that the field inside a conductor is always zero . So when current passes through a wire , the electricity only passes through the surface of the conductor . In ...
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14 views

Electrostatic energy of the system

Problem : $(A)$ There are two thin concentric metallic shells of radius $a$ and $b$ $(b>a)$. Inner shell carries a total charge $Q$ and the outer shell carried a total charge $–Q$. Calculate the ...
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14 views

How to find the polarization (phase) of the virtual source if image theory is used

Consider a radiating element (actual source) is placed above a ground plane, and if we apply image theory to determine the E-filed, the virtual source will be placed below the ground plane and ground ...