Electrostatics is concerned with the field and potential of stationary electrical charges and electric charge distributions. Problems are this type are almost exclusively concerned with mathematics of geometries using the inverse-square law.

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Is there a charge across all space? [duplicate]

We're studying electrostatics in class, and the teacher introduced us to Gauss' Law a few days ago as $$\int \vec{E} \cdot \mathrm{d}\vec{A} = \frac{Q}{\epsilon_0}$$ Now suppose that the entire ...
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Two uniformly charged spheres are superposed with slight displacement. What's the surface density?

*Note: This is from the Second Volume of Feynman's Lectures on Physics : Mainly Electromagnetism and Matter And this is the excerpt from the book: If the relative displacement of the two spheres ...
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What is the electric field near an infinite sheet with a point charge near by? [closed]

The electric field near a negatively charged conducting infinite sheet is $\frac{-\sigma}{2\epsilon}$. If we add an equally charged positive particle some distance $r$ away from the sheet, the field ...
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Can a human be killed by electro-static discharge while performing daily chores? [closed]

During freezing-winter seasons, as soon as I reach my office and get off the warm-clothing; I get an electrostatic discharge whenever I touch a metallic water-fountain in my lab. The shock I get is ...
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What determines how much electrical charge an object can hold?

What determines how much electrical charge an object can hold? Does increase voltage force more electrical charge to be store in an object (Van de Graaff generator), since electric field increase as ...
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Can two electrons get ever so close as to touch each other?

My friend and I were studying for our EM test when we started to think about what happens to the electric field near an infinite line of charge. $$E = \frac{\lambda}{2\pi\rho\epsilon_{0}}$$ As you ...
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Electric potential energy and signs

I know that electric potential is negative near a negative charge and positive near a positive charge. But does this mean a small positive 'test' charge has a negative electric potential energy near a ...
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33 views

Parallel plate capacitor

How does a parallel plate capacitor emit a constant electric field between its plates? Isn't the electric field governed by an inverse square law? Then what would happen if I put a charged particle ...
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Measurements from inside conductors

We have known for some time now that when electric field is applied across any conducting shell, then electric field inside it would be zero. It also has some fantastic applications such as ...
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In low voltage (3-12V) DC applications, which is safer to be exposed or touchable + or - terminal?

The - side has a surplus of $e^{-}$s and the opposite is true for the + side of the power supply. Does it not matter, or depends on your configuration / contact with Earth? Please explain!
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What is the answer to Feynman's Disc Paradox?

[This question is Certified Higgs Free!] Richard Feynman in Lectures on Physics Vol. II Sec. 17-4, "A paradox," describes a problem in electromagnetic induction that did not originate with him, but ...
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How can I split a resultant force into its $x$ and $y$ components?

Point charge 3.5μC is located at x = 0, y = 0.30 m, point charge -3.5μC is located at x = 0 y = -0.30 m. What are (a)the magnitude and (b)direction of the total electric force that these charges ...
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How does an electron undergoing uniform circular motion exactly lose energy?

One of the main reasons for the failure of the Rutherford model of atomic structure, it is famously stated, is that the electron undergoing circular orbit loses energy since due to its centripetal ...
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phase difference between incident plane wave incident on a dipole and radiation fields from dipole

i have an incident plane wave and a dipole, consider that plane wave incident on dipole. at this moment what happen for dipole ? we know that after incident of plane wave on dipole, the radiation have ...
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Does Gauss' Law apply to real physical solid conductors?

In a conductor there is no electric field because there is no charge. There is no charge inside because any charges present inside would repel each other and be driven to the surface of the conductor. ...
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The electric field of a conductive sphere containing a charge - grounded vs not grounded

Let's suppose we have a sphere but unlike theoretical ones it'll have some thickness say $\Delta r$ and inner radius $R$. What I was wondering about is how will it behave if we place some charge $q$ ...
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3answers
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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 ...
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Physical representation of magnetic vector potential

For time varying potential $$ E= - \nabla(v)- \frac{\partial A}{\partial t} $$ now for scalar potential v we can represent the equipotential surface as a perpendicular surface of the direction of ...
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How to find whether the electric field between capacitor plates is above or below the electrical breakdown limit of the insulator between the plates?

Let's say the two plates of a capacitor have charges $q_1$ and $q_2$. The separation between these plates is $d$. I know that I can calculate the electric field by dividing the voltage that is applied ...
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Binding Energy of an Electric Dipole

My question is structured in two parts: Is there any way to isolate the charges of an electric dipole? What is the binding energy of an electric dipole? To put it in another way, is there ...
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1answer
28 views

Does magnitude of a charge influence magnitude of force that individual charge exerts on another charge [closed]

two point charges, q1 and q2, are placed 0.3m apart on the x-axis, as shown in the figure above. Charge q1 has a value of -3 nano Coulomb and q2 has a value of +4.8 x10^-8 C. The net electric field ...
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Is a given charge density a surface charge density or volume charge density?

The exact question goes like this: In a certain electronic tube, electrons are emitted from a hot plane metal surface, and collected by a plane metal plane parallel to the emitter, at a distance ...
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Prove a dielectric with infinite dielectric constant behaves as a conductor for static fields

I read the following problem: Prove that a dielectric medium for which $\varepsilon \to \infty$ behaves as a perfect conductor in the presence of static electric fields. So, the easy part is that the ...
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Image charge method to find electric field [closed]

The following is a question from my tutorial on boundary value problems and image charge method- A point charge +q is placed at (0, 0, d) above a grounded infinite conducting plane defined by z = 0. ...
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Circuit breaker Trips during thunderstorm

The circuit breaker at the electrical mains trips at home when there is a thunderstorm outside. Why does this occur?
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Electric flux through nonspherical surphace

Here's an explanation from a book that I read: Now, I have a few problems with this explanation as well as with the "cone method". I guess that all my problems boil down to the concept of ...
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1answer
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Electrostatic Potential Energy Integral

I'm trying to calculate the total energy of a simple two charge system through the integral for electrostatic energy of a system given in Griffiths' book: $$U = \frac{\epsilon_0}{2}\int_V E^2 dV .$$ ...
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electrostatics particle charging

When ash particles are charged negatively ( corona charging, ionization, tribo electric ) and then collected on to the fabric; particles arrange themselves in porous dendritic structure whereas ...
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Is there a place on the equipotential surface where a charge feels no electric force? [closed]

I'm given a graph of an equipotential surface where I need to find a place where a charge feels no electric force. I feel like it will be where the voltage is zero, which would be 2G on the graph, ...
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1answer
229 views

Force due to combination of free space and dielectric

I will make a generalized form of my question. There are two point charges $q$, $x$ distance apart. And there is a dielectric slab of thickness $t$ and of dielectric constant $K$. Should the force ...
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Will a charged capacitor discharge if one lead is connected to ground?

If I charge a capacitor and connect one lead to ground keeping the other lead floating, will the capacitor discharge ? ...
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77 views

Why isn't the electric field just a mathematical tool?

I'm limiting my question to this field because it is the only one I know of with a certain degree of knowledge. I doubt they really exist because of the following reasoning: Coulombs law was stated ...
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Curvature of electrostatic potential is zero

Could you please expound upon this claim? I found such claim on Zangwill's Classical Electrodynamics, which states that constraint coming from Laplacian equation implies electrostatic potential has ...
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Why is the shape of lightning or an electric spark a zig-zag line?

Why is the shape of the lightning (or an electric spark) always of a zig-zag nature? Why is it never just a straight line? Image source.
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Conductors and Uniqueness Theorem

I'm working with Griffiths Electrodynamics, and he introduces a uniqueness theorem: First Uniqueness Theorem: The potential $V$ in a volume $\Omega$ is uniquely determined if (a) the charge ...
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1answer
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Does Gravity Warp Coulomb's force?

Does gravity effect the "sphericalness" of the Coulomb force? For example, is the field 1 meter above a charge weaker than the field 1 meter below the charge? Could a 0.014% difference in the field ...
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How does electrostatic force affect electronic devices?

How does electrostatic force generated by two seperate plates having opposite charges affect electronic devices? I know that magnetic fields have some harmful effects to electronic devices but I am ...
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1answer
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Using Maximum Principle to see conductor is equipotential

This is a problem from electrostatics, but I'm trying to understand it in terms of harmonic functions. Let $B\subset\mathbb{R^3}$ be a conductor. It can be shown that the electric potential ...
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What is special about the ratio $Q/V$ that we give it the name Capacitance?

Why is the ratio Charge/Potential important? Also, usually when we add charge, the potential changes. Then why do we care how much charge we can put on a conductor for a given potential.
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Electric field from conductive to dielectric media

I am interested in the main difference between transitions from electric fields from Conductive to Conductive/ Dielectric to Dielectric and Dielectric/Conductive media. What are the boundary ...
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1answer
69 views

Does charge of a metal charged by induction determine by which ends of the metal is grounded to?

Does charge of a metal charged by induction determine by which part of the metal is ground to? I draw a diagram to make it simple to understand: Right diagram: When ground is touched with the ...
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206 views

Finding Green function using eigenfunction expansion method

Given the Dirichlet boundary condition, I am to show that the functions that satisfy $(\nabla ^2 + k_{lmn}^2) \psi_{lmn} (x,y,z) = 0$ are given by $\psi_{lmn} = (\frac{\pi}{2x})^{1/2} J_{l+1/2}(x) ...
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Why static electricity only concentrates and flows on the surface?

Anything insides Faraday Cage or Faraday Suit is protected from Electric Field outside. I don't understand what restricts the flow of free electrons to surface on the cage only? How does that happen? ...
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521 views

How do I express the interaction energy between two charged spheres?

Consider two identical insulating spheres each with radius $R$ and uniform charge $Q$ through their volume. They are separated from their centers by a distance of $d>2R$. Here is my general ...
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2answers
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What is the minimum distance between two opposite point charges

In an overly simplistic model if I have a single negative charge, and a single positive charge they will be attracted. I expect they will fly together. Click. Good luck getting them apart. The ...
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1answer
146 views

Earnshaw's theorem and springs

Earnshaw's theorem states that the Laplacian of the potential energy of a small charge moving through a landscape full of static negative and/or positive charges (and gravity) is zero. Thus you can't ...
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1answer
59 views

How to find the electric field of a charged tube?

Let's say there is a charged tube(cylinder with no top or bottom) with radius $a$, length $l$ and charge $q$ and a point which is collinear with the centre of the charged tube. Anyway, since we can ...
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1answer
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Find the field of two infinite strips of width $b$ [closed]

Q:The two charged strips in the following picture have width $b$, infinite height,and negligible thickness(in the direction perpendicular to the page).Their densities per unit area are $\sigma$ ...
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275 views

Effect of charges near a parallel plate capacitor

If I charged a parallel plate capacitor. And then, I insert a charged body near one of the plates. Will there be any interactions like attraction or repulsion? What if I disconnected the battery?
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Can you get a static shock in a vacuum if you are not touch the object?

For example when you hop on a trampoline sometimes you will be shocked before you even touch the tramp. Does the shock have to pass through the air to get to you or can it work in a vacuum?