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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Rusting of induction hardened portion when the non hardened portion is chrome plated [closed]

When a ferritic steel component that has a portion of it induction hardened and quenched in oil is chrome plated over the non hardened portion, I see rust formation after some time on the induction ...
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Regarding the zero internal electric field in a conductor (electrostatic case)

Let's say we have a homogenous electric field in the $z$-direction. For computational simplicity let's say we have a thin sheet of metal covering entire the $x$-$y$ plane. The answer here is straight ...
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Radius of sphere formed by equipotential surface of point dipole [closed]

One of the Equipotential surface formed by point electric dipole placed in parallel electric field forms a sphere enclosing the dipole.how to find the radius of the sphere?
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Charged Particles: How is energy conserved?

I can seem to understand where the energy comes from when two particles accelerate. I tried searching through the forums and it seems like the answer is always potential energy was the source of ...
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1answer
126 views

What is the significance of the Inverse-square law? [duplicate]

Considering its occurrences in various fields like Electrostatics, Gravitation, Acoustics etc. how does the law bind these topics together?
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1answer
63 views

Can we derive Biot Savart law from Coulomb's law?

Can we derive Biot Savart law from Coulomb's law by setting a current source at an instant in place of one of the charges? Let's say $dl$ is the length of the conductor having $dQ$ charge which ...
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1answer
30 views

Electric Field of Bar [closed]

Problem: Positive charge $+Q$ is distributed uniformly along the positive $x$ axis from $x = 0$ to $x = a$. Negative charge $-Q$ is distributed along the $-x$ axis from $x = 0$ to $x = -a$. A point ...
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2answers
54 views

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
93 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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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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1answer
37 views

Weight of sphere in kerosene [closed]

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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45 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
38 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
39 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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1answer
53 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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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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27 views

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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1answer
37 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
12 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
62 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
43 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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1answer
188 views

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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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
43 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
86 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
29 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
71 views

Why does the divergence of the Poynting 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
50 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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130 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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12 views

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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2answers
46 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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1answer
29 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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43 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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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
31 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
26 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
87 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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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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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 ...
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2answers
91 views

Problem understanding energy of a electric field

I just finished classical mechanics, and waves and have started electromagnetism. I have studied upto electric fields, potentials and conductors in a static field and have just entered capacitors. And ...
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3answers
34 views

How to determine the concentration and sign of the charge carriers in copper

I need to design a procedure for an experiment to determine the concentration and sign of the charge carriers in copper. I'm given: A slab of copper 2.0 mm thick, 1.5 cm wide, and 4 cm long One very ...
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2answers
31 views

Static electricity - what is it?

I'm just having some difficulty with completely understanding the concept of static electricity. What actually happens? Is it because the electrons cant move? And if so, why can't they move?
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3answers
42 views

Need help with signs (+ -) in electric potential work and potential energy problem

The problem is from Sears and Zemansky's University Physics, 12th edition in Spanish. The problem says: How much work is needed to assemble an atomic nucleus that contains three protons if it is ...
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1answer
56 views

Divergence of $\frac{e^{-br}\hat{r}}{r^2}$ in electrostatics [closed]

My question is how to calculate the divergence of a vector field (Electric field) given as: $\vec{E}(r)=\frac{e^{-br}\hat{r}}{r^2}$. Or more generally how to approach finding the divergence of a ...
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66 views

Why does there have to be an electric field if there is potential difference?

I read in a few books that there is always an electric field if there is an electric potential. I went through this but the question on this page only states that there is an electric field and it is ...
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1answer
37 views

How do flames neutralize a static charge?

I was working with a demonstration galvanometer recently when it accidentally picked up a static charge from me lightly rubbing my hand across it. The case was made of a clear plastic. My attempts ...
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2answers
52 views

Why doesn't the gravitational force have a permittivity in its formula? [duplicate]

We know that the electrostatic force between two charges depends on the medium between the charges and its permittivity. Why, then, doesn't the gravitational force depend on the medium?