# Tagged Questions

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 scalar quantiy or vector quantity

I cross referenced some website yahoo answers, wikipedia & some other websites. They were providing different answers. I know that electric field intensity is a vector quantity. But what abt ...
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### Can two charges with same sign atrract?

Can two charges with same sign (++/--) separated by some finite distance attract each other ?
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### How do you know when you need to use distributions to represent charge densities? [closed]

I tried to solve a problem using Gauss' law in the following way. Let's assume we have a spherical shell of radius $R$ with a charge $Q$ being homogenously distributed on its surface. I am trying to ...
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### Confusion in understanding the proof of Uniqueness Theorem

I am having problems in comprehending the proof of contradiction used by Purcell in his book; ...We can now assert that $W^1$ must be zero at all points in space. For if it is not, it must have a ...
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### Doesn't Laplace's equation describe the local property of space?

$$\nabla^2 \phi = 0$$ is Laplace's equation used "wherever $\rho = 0$, that is in all parts of space where there is no electric charge.". However,how can Laplace's equation be used outside a conductor ...
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### Variations in electric field of a light speed charged particle

From the question " Is there a travelling speed of for electric field? If yes, what is it?" I get to know electric field propagates at speed of light. What if a charged particle which creates this ...
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### Charge between parallel plates given voltage

When you connect a parallel-plates capacitor to a voltage source, why is it assumed that the plates will have equal but opposite charge? According to the formula, the voltage only fixes the charge ...
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### Electric potential between two infinite plates

Below is a solved exercise from Griffiths' Electrodynamics. I don't understand why it's directly assumed that the configuration is independent of $z$. Shouldn't there be a contribution from it since ...
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### Why is the y-component of electric field of a uniformly-charged disk near its center the same as that of infinite sheet of charge?

This is an excerpt from Edward M. Purcell's Electricity & Magnetism: As $y$ approaches zero from the positive side, $E_y$ approaches $\dfrac{\sigma}{2\epsilon_0}$. On in the negative side of ...
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### Why is energy associated with the electric field given as $U = \dfrac{\epsilon_0}{2} \int E^2 dv$?

This is an excerpt from Edward M. Purcell's Electricity & magnetism: Suppose a spherical shell of charge is compressed slightly, from an initial radius of $r_0$ to a smaller radius. This ...
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### Gauss' Law and area vector

Recently I've been doing some physics exercises on electric and magnetic fields and read up somewhere that the vector area of a closed surface is equal to zero. That made me wonder why, when using ...
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### Electrostatic potential due to two charge system

When we calculate electric potential energy of a two particle system, say first I bring $+q_1$ and then I bring $+q_2$ against $q_1$'s electric field. Say I get that $q_2$ charge to a point $r$ ...
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### Why is the Electric Field Zero at this point?

In a Phet Lab simulation, which is all I have at the moment to do my learning on electric field forces, the point represented as colored on the diagram below is shown to have an electric field ...
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### How can a point hold mass or charge where it doesn't tell anything except position? [duplicate]

In geometry point is a dimension less quantity as it doesn't have length, breath or height. But when we define columbs law in electrostatics, we define points holding charges or Newton's law of ...
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### Why charge distribution is greatest at pointy edges of a surface? [duplicate]

If we have a conductor which is in electrostatic equilibrium, then the charge distribution over this surface $\sigma$ is greatest at the sharp edges of that surface. Why is this the case? I want ...
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### can a power supply with high voltage value and some current be split into multiple small voltages of same current?

For example: if I have a source that can give an output of 10,000 Volts with some unknown current value, now, can i make that 10,000 Volts to 50 (need not be 50 exactly but maybe more than 30) of 200 ...
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### How can I have a voltage in hall effect with zero magnetic field?

How can we obtain a voltage with no magnetic field is applied to the semiconductor? They told me that if the points where I measure the potential difference are not at the same level I would obtain a ...
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### Charge Distribution Across A System Of Metallic Parallel Plates

While calculating the charge distribution across a system of metallic plates, (taught as a prequel to the parallel plate capacitor), we say that the electric field inside each plate must be zero. We ...
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### Sphere of electric charge revisited

I am thinking about a sphere of homogeneous charge distribution (see Electric field due to a solid sphere of charge, for example). Here we use a Gaussian surface (blue area) to find the electric ...
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### What is the cause of the time-varying electric and magnetic near-fields around a wire with a 60Hz AC current?

I know that it's the accelerating electrons in an AC current that are the cause of far field effects. But, what about the reactive near field close to a wire that has a 60Hz AC current? What is the ...
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### What happens to half of the energy in a circuit with a capacitor?

For a simple circuit with a battery supplying a voltage V to a capacitor, let us assume that the charge on the capacitor is Q. Now, the work done by the battery or the energy supplied is given by the ...
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### Calculating rise in water surface due to a charged capacitor

﻿Two metal plates separated by a distance d & initially charged with charge +Q & -Q are kept so that it just touches the surface of a very large water tank as shown in figure a. Thus water ...
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### What does a hexadecapole look like

Two dipoles can form a quadrupole, two quadropoles an octopole. The textbook by Griffith then says ' and so on'. So how would a hexadecapole really look like? My impression was that the construction ...
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### Origin of internuclear forces

I just recently read about the existence of internuclear forces as the reason for the nucleus to remain 'stable' as in it doesn't separate out into protons and neutrons even though there is electronic ...
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### Application of Coulomb's Law

I've just finished reading a section in a book on Coulomb's Law. I'm trying to practice the math a bit and came up with the following: Suppose you have two charges, -5uC ($q_1$) and 7nC ($q_2$). ...
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### Why does the Electric Field of a dipole have no $x$ component?

According to the solution $2E\sin(\theta) = E_{net}$. I understand how the dipole works but I don't understand why the x component would be 0?
I am working on a problem that states the following: Imagine an infinite straight wire carrying a current $I$ and uniformly charged to a negative electrostatic potential $\phi$ I know here ...