What is Electrostatic: Definition and 879 Discussions
Electrostatics is a branch of physics that studies electric charges at rest.
Since classical physics, it has been known that some materials, such as amber, attract lightweight particles after rubbing. The Greek word for amber, ήλεκτρον, or electron, was thus the source of the word 'electricity'. Electrostatic phenomena arise from the forces that electric charges exert on each other. Such forces are described by Coulomb's law.
Even though electrostatically induced forces seem to be rather weak, some electrostatic forces such as the one between an electron and a proton, that together make up a hydrogen atom, is about 36 orders of magnitude stronger than the gravitational force acting between them.
There are many examples of electrostatic phenomena, from those as simple as the attraction of the plastic wrap to one's hand after it is removed from a package to the apparently spontaneous explosion of grain silos, the damage of electronic components during manufacturing, and photocopier & laser printer operation. Electrostatics involves the buildup of charge on the surface of objects due to contact with other surfaces. Although charge exchange happens whenever any two surfaces contact and separate, the effects of charge exchange are usually only noticed when at least one of the surfaces has a high resistance to electrical flow. This is because the charges that transfer are trapped there for a time long enough for their effects to be observed. These charges then remain on the object until they either bleed off to ground or are quickly neutralized by a discharge: e.g., the familiar phenomenon of a static "shock" is caused by the neutralization of charge built up in the body from contact with insulated surfaces.
Hello all,
I am interested in placing a static charge on a conductor by means of an electrical circuit. One way to do this is by means of a Van de Graaff generator which uses the triboelectric effect to generate net charges, then places them onto two conductors having equal but opposite...
Homework Statement
The figure shows a section of a cylindrical surface, height h and radius R. The curved surface extends from the z-axis to the y-axis only and has a charge density given by σ(z)= σ0z where σ0is some constant. ind the electrostatic potental at a. (a is at the origin)
I'm...
I have a hot gas with a net negative charge that I want to keep contained using an electric field. My question is how do I calculate the electric field strength necessary, and how would one go about producing it?
Homework Statement
Compare gravitational, electrostatic and van der Waals forces between two 100nm polystyrene spheres which are separated by a) one micrometer b) one millimetre and c) one centimetre
Homework Equations
Gravitation and electrostatic equations are standard.
The...
I am having difficulty ascertaining the difference between an electrostatic charge present on the surface of a conductor and the flow of an electron current (or holes, if you prefer) along the surface of a conductor with respect to their effects on the electron density of states (and, more...
I want to apply a net electrostatic charge with controlled constant voltage (polarity switchable as well) to a conductor. The conductor will continually be charged by friction, so I want to have a circuit apparatus operating on it to continually re-supply or drain charge as needed. Does such a...
Hello everyone,
I am thinking of a nice experiment that can be done in high school laboratory. It is not obligatory for them to include calculations, they just have to be easily conducted without expensive equipment and relatively safe. The main purpose is to make students learn through...
Homework Statement
When books of elctromagnetism talk about Electrostatic equilibrium，they say electric charges will keep moving if electric field in the conductor doesn't equal to zero utill it does.However,what if there are no excess free charges in the area where that doesn't equal to...
Homework Statement
a) Calculate the electrostatic force on an uniformly charged rod of length 2L and charge q, which lies along the axis of an uniformly charged ring of radius R and charge q'. The centers of the charged rod and the rings are displaced at a distance z= z0.
b)Show that if z0 >>...
Homework Statement
Two large flat parallel sheets have opposite uniform surfacecharge densities ±σ and are separated by a distance d. Alarge uncharged conducting slab of thickness d/3 is parallel thethe charged sheets, centered between them. Find the electrostaticpotential as a function of...
Homework Statement
There are four charges, each with a magnitude of 2.1 µC. Two are positive and two are negative. The charges are fixed to the corners of a 0.25 m square, one to a corner, in such a way that the net force on any charge is directed toward the center of the square. Find the...
Homework Statement
Homework Equations
F = k*Q1*Q2/r^2
The Attempt at a Solution
My work is E(x) = (k*Q1)/(x^2) - (k*Q2)/((L-x)^2)
Find derivative and set E(x) = 0. But I get a non real answer. Am I doing this completely wrong here? I was going to solve for x here.
When an electron and a positron annihilate, they typically produce two gamma rays, each of energy mc^2 plus whatever kinetic energy available before annihilation. I was recently told that it is an experimental fact that the electrostatic energy between the electron and the positron does NOT...
So, when I was learning about static electricity and induction and conduction, there were several labs done where a pith ball or electroscope could be manipulated through induction when a charged object was placed near it.
In the case of the little pith ball, a negatively charged piece of PVC...
Homework Statement
Two dust particles are separated by 0.01m and of the same mass and charge, find the total potential energyHomework Equations
E_{el}=k\frac{q_1 q_2}{r}
E_{grav}=-G\frac{m_1 m_2}{r}
r=0.01 m, q_1=q_2=1.1201\times10^{-18} C m_1=m_2=13\times10^{-9} kg
Where G and k are the...
Homework Statement
I am confused b/w two questions:
1) The mass M of a planet Earth is uniformly distributed over a spherical volume of radius R. Find and expression for the energy needed to disassemble the planet against the gravitational pull amongst its constituent particles.
2) A metal...
Homework Statement
In fair weather, over flat ground, there is a downward electric field of about 150 N/C. A) assume that the Earth is a conducting sphere with charge on its surface. If the electric field just outside is 150 N/C pointing radially inwards, calculate the total charge on the...
A conductive plate with no initial charge is put between two identical positevily charged plates. Is it possible that the plate which is put between those two plates configures a situation where the net force acting upon each plate is zero? (the third plate could have different dimensions then...
Homework Statement
Measurements show that a honeybee in active flight can acquire an electrostatic charge on the order of 90.9 pC.
a)How many electrons much be transferred to produce this charge?
Ne =5.67*10^8
b) Supposing two bees, both with this charge, are separated by a distance of 14 cm...
I am having trouble with this question and need some help please excuse any mispellings
the question deals with three charges q1 q2 and q3
q=1.2*10^-5
q1=+q or 1.2*10^-5
q2=-2q or -2.4*10^-5
q3=+3q or 3.6*10^-5
q1 and q3 are exactly .32 meters apart and I need to find what...
Homework Statement
Two small objects, A and B, are fixed in place and separated by 2.46 cm in a vacuum. Object A has a charge of +1.18C, and object B has a charge of -0.937C. How many electrons must be removed from A and put onto B to make the electrostatic force that acts on each object an...
Homework Statement
Of the charge 'Q' initially on a tiny sphere, a portion q is to be transferred to a second, nearby sphere. Both spheres can be treated as particles. For what value of q/Q will the electrostatic force between the two spheres be maximized?
The Attempt at a Solution
The...
The question is like this:
8 charges of magnitude q and different sighs are placed at corners of a cube of side a.
Find the work done in taking them far away from each other.
Homework Equations
U = kq1q2/r
W = ΔU
The Attempt at a Solution
First i found out the potential energy...
Homework Statement
Suppose that two balls of mass 1.5x10-4kg each carry equal charges and are suspended by identical threads of length 11cm anchored 28cm apart. If each thread makes an angle of 20 degrees with the vertical, what is the charge on each ball?
Homework Equations
F=kq2/r2The...
A proton is in a vacuum near the surface of Earth. Where should a second proton be placed so that the electrostatic force it exerts on the first proton balances the weight of the first proton?
F = (k×Abs[q1]×Abs[q2]) / r^2
k = 8.99×10^9 Nm^2/C^2
Hi,
I am trying to do the multipole expansion of a point charge away from the origin, I can't understand Legendre polynomials so want to do it in Cartesian but when I try to Taylor expand
the \left|\frac{1}{\vec{r}-\vec{r'}}\right| I am not sure how to handle the modulus.
Any help...
Homework Statement
During a collision between two initially uncharged polystyrene balls of radius 2 mm, some electrons are transferred from one of the balls to the other. In what direction does the resulting electrostatic force between the balls act?
The magnitude of the force between the...
Homework Statement
Here is the problem :
http://i1200.photobucket.com/albums/bb327/loba333/untitled.jpg
ill write it out again aswell
A particle with charge +9 μC is placed at the origin, and another particle of charge –2 μC is at x = L. At what two points is the net electrostatic potential...
Homework Statement
A mad scientist is designing a trap for intruders that will lift them up into the air and hold them helpless. The device consists of an equilateral triangle, 10.0 meters to a side, embedded in his floor. When he flips a switch, the corners of the triangle will be charged...
Homework Statement
The attractive electrostatic force between the point charges 8.12×10−6C and Q has a magnitude of 0.670N when the separation between the charges is 7.26m.
Find the sign and magnitude of the charge Q.
(this is a direct cut and paste)
Homework Equations...
At equilibrium, a conducting object will have no electric field, current or excess charge in its interior. There's a fairly simple derivation for how an initial (non-equilibrium) interior charge density d0 falls to zero exponentially with time t when the conductor approaches equilibrium. For a...
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Suppose we have a conducting shell (which is not necessarily a sphere) and no electric charge inside.
Is the electrostatic field inside the conducting shell always zero? (even if there is some charges outside the shell)
What if the shell is grounded?
If the answer is yes, how it...
What comprises the electrostatic field? Electromagnetic radiation is made of photons, but what about the electrostatic field? Two static charges exert forces on one another, through their E-fields, presumably through photon exchanges. I am having trouble forming an idea of what an...
Everyone knows that the potential difference between two points 1 and 2 is given by \int_{1}^{2}{\vec{E}}\cdot d\vec{l}. My question is that can we calculate the potential difference between two point charges by this formula? Say, one of them is +ve charge and the other is a -ve charge...
Homework Statement
Well we just learned about Coulomb's Law today but there is something that is bothering me. According to Coulomb's Law the magnitude of the force of attraction between a charged and neutral object is 0. However, the Law of Electrostatics states that a charged and neutral...
Homework Statement
Consider a phospholipid bilayer membrane consisting of a mixture of 90% uncharged lipid and 10% singly charged acid lipid. Assume 68 Å^2 surface area per lipid head group, and assume further that the charged lipids are uniformly distributed and immobile. The membrance is...
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I am trying to fully wrap my head around signal shielding so as to take it from the trial-and-error domain to the theoretical design domain. The problem is that I am stuck on one of the very basic and fundamental principles of shielding - the floating conductor as an electrostatic...
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Working on a little project, just some electrostatic plasma confinement, and the high energy plasma is being expelled out a nozzle, and a colleague of mine proposed that we use an electron beam through the center of the nozzle, the nozzle already having a bit running down the center that...
There is known effect when electric field bends water stream:
http://www.school-for-champions.com/science/static_induction.htm"
Does that mean that moving water inversely affect electric field?If yes,could we make electric generator in which moving water would affect electric field and...
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How to increase electrostatic force?
I am from grinding wheel industry, on one process grains are placed on the belt conveyor. Below this conveyor aluminum sheet is connected with 11 KV power supply. Then backing disc is brought near the conveyor. then...
Homework Statement
"In class we calculated the electrostatic self energy of a uniform density sphere of charge, i.e., the work required to assemble the sphere from "infinite dispersal." Along the same lines, calculate the electrostatic self energy of a spherical shell of charge, of negligible...
Suppose we have three charged particles arranged in a line, the first one being negative, the second being positive, and the third being negative.
If we want to find the net force on the third particle, we sum the force from the second particle on the third and the force from the first...
Homework Statement
I'm looking at Y.K.Lim's Problems and solutions in Electromagnetism and there's one thing that's confusing me:
[PLAIN]http://img545.imageshack.us/img545/2218/capturegb.png
Homework Equations
Where does the square in r comes from? When in the beginning it says...
I hace read in Electrodynamics from griffiths chapter 2, that, whenever acavity is inside an spherical conductor, for the outside it acts as if there was a point cherge at the center...
But what if thew conductor has another shape, for example a revolution ellipsoid...?? how do you deal with...
Assume that you have two protons accelerated in opposite directions within a cyclotron. As they approach the speed of light their masses increase. At what proportion of the speed of light will their gravitational attraction (due to their increased mass) equal their electrostatic repulsion ?
Thinking in terms of electric circuits and electrostatic potential I understand how an electric current arises as manifestation of a difference in potential. How does this work at a more microscopic level? I.e. how does an electron know what potential it's environment is at?
E.g.: If I...
Hi there,
Lately, I've been trying to gain a deeper understanding of the relationship between the Coulomb force F, electric field E, electric potential V, and electrostatic potential energy U.
In regards to electrostatic potential energy, as I understand it, if you had, say (made up a few...
Electrostatic Forcce :(
Homework Statement
In Fig. 21-26, particle 1 of charge q1 = +1.4 µC and particle 2 of charge q2 = -4.2 µC, are held at separation L = 12 cm on an x axis. If particle 3 of unknown charge q3 is to be located such that the net electrostatic force on it from particles 1 and...
Homework Statement
Identical isolated conducting spheres 1 and 2 have equal charges and are separated by a distance that is large compared with their diameters (Fig. 21-22a). The magnitude of the electrostatic force acting on sphere 2 due to sphere 1 is F = 6.5 N. Suppose now that a third...
Homework Statement
How far must two protons be placed on the Earth’s surface for there to be an electrostatic force between them equal to the weight of one of the protons?
Homework Equations
The Attempt at a Solution