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.

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  1. D

    Help with an electrostatic problem

    Hi I cannot get this problem for the life of me and I have no idea why Four charges q1 = q3 = -q and q2 = q4 = +q, where q = 5 µC, are fixed at the corners of a square with sides a = 1.3 m Calculate the x- and y-components of the net electric field at the midpoint M of the bottom side of...
  2. I

    Electrostatic Force question

    Homework Statement Three charges are fixed to an x, y coordinate system. A charge of +18 µC is on the y-axis at y = +3.0 m. A charge of -16 µC is at the origin. Lastly, a charge of +45 µC is on the x-axis at x = +3.0 m. Determine the magnitude and direction of the net electrostatic force on...
  3. J

    Any help with an electrostatic field manipulation design or suggestions?

    I have about a year of electronics background, but what I'm trying to make is still a bit daunting for me. I want to build a device that creates a very high voltage electrostatic field like a van de graff generator and then input to this field variable frequencies from an electric keyboard...
  4. R

    Understanding Electrostatics: Exploring Charge Induction in a Hollow Sphere

    Some teacher told me this If we have hollow sphere (of conducting material) with some thickness. and if we place a +ve charge inside that . -ve charge induces on inner surfuce, Which further causes in outer sphere & that becomes positivly charged. is this right? Please give right explanation.
  5. L

    Electrostatic containment (impossible)

    I just came across Earnshaw's Theorem which states: A charged particle cannot be held in stable equilibrium by electrostatic forces alone. As an example it said that equal and fixed point charges at the corners of a cube could not hold stationary a point charge at the center. There was...
  6. P

    Solve Electrostatic Force Problem

    TITLE: Hard Electric Charge Problem. Homework Statement 15. The charges and coordinates of two charged particles held fixed in an xy plane are q_{1} = +3.0 \muC, x_{1} = 3.5 cm, y_{1} = 0.50 cm, and q_{2} = -4.0 \muC, x_{2} = -2.0 cm, y_{2} = 1.5 cm. Find the (a) magnitude and (b)...
  7. K

    Can Electrostatic Induction Remove Dust Under an iPod Screen?

    hi... actually, i got dust under my ipod screen,,, I've been searching for was to remove it without getting it naked... so i thought of electrostatic induction... i thought that, rbbing a pen with my hairs and then approaching it to my screen, the dust particles would be moving at least...
  8. G

    Electrostatic and Gravitational Forces

    *Thanks for the help*
  9. C

    Deriving equation for electrostatic force.

    Homework Statement Basically I am given an image showing a test charge tied to a string where there is the ball is stationary. I need to use the fact that there is no net force on the ball to derive an equation for the electrostatic force in terms of g, the angle, and the mass of the ball...
  10. C

    Electrostatic charges on a cotton yarn

    Usually, in textile industry, the important issue is to discharge the yarns from any electrostatic charges that might be stuck on it due to friction or other factors. What I need is completely the opposite; I want to put, on a yarn, electrostatic charges strong enough to make the yarn stuck on a...
  11. MathematicalPhysicist

    Mutual Electrostatic Energy Derivation.

    i don't quite understand the derivation of mutual electrostatic energy of two charged system: U_12=\frac{1}{4\pi}\intE_1(dot)E_2dV=-\frac{1}{4\pi}\intE_1(dot)\nebla\phi_2 dV= \frac{1}{4\pi}\int \phi_2(dot)\nebla(dot)E_1=\int \phi_2*\rho_1dV i undersantd that we are using here...
  12. B

    Electrostatic force problem in Newtons

    Three charges are fixed to an xy coordinate system. A charge of +14 uC is on the y-axis at y= +3 m. A charge of -14 uC is at the origin. Lastly a charge of +47 is on the x-axis at x= +3 m. Determine the magnitude and direction of the net electrostatic force on the charge at x= +3 m. Specify...
  13. wolram

    Electrostatic Wall: David Swenson's 3M Anomaly

    I came across this by accident. http://amasci.com/weird/unusual/e-wall.html. David Swenson of 3M Corporation describes an anomaly where workers encountered a strange "invisible wall" in the area under a fast-moving sheet of electrically charged polypropelene film in a factory. This...
  14. G

    Calculating Electrostatic Pressure from Metal Sphere

    I have a metal sphere with the net charge q. And I'm trying to calculate the force that southern hemisphere exerts to northern hemisphere... and I get 0. now, the electrostatic "pressure" is \mathbf f = \sigma \mathbf E = (q/4\pi R^2) (q/4\pi \epsilon_0 r^2) \mathbf {e_r} due to the symmetry...
  15. F

    Solve the Electrostatic Paradox: Find Finite Value of E

    I tried to do a post here but it didn't take so I'm going to put something much shorter that asks the same thing. I tried to calculate the electric field produced by a sphere of uniform charge using this formula: E(r)=\frac{1}{4\pi\epsilon_0} \iiint\rho(r') \frac{r-r'}{|r-r'|^3} d^3r' I...
  16. P

    Electrostatic force and # of elementary particles

    I need to find the electrostatic force & the number of elementary particles between two charged balloons held in the center of their strings (Think of an Isosceles Triangle). Homework Statement Mpurple(balloon) - .00354 kg Mred - .00405 kg Lpurple - .725 m Lred - .68 m θ = 16° T =...
  17. W

    Electrostatic potential energy for concentric spheres

    Two concentric metal spheres have radii r_1 = 10 cm and r_2 = 10.5 cm. The inner sphere has a charge of Q = 5 nC spread uniformly on its surface, and the outer sphere has charge -Q on its surface. (a) calculate the total energy stored in the electric field inside the spheres Hint: You can treat...
  18. V

    Y-component of Electrostatic Force

    Homework Statement Calculate the X, Y, and magnitude force between the two charges. Compare to the computer simulation results. Homework Equations Do not forget that this is a 2-D problem. Use the 2-D Coulomb’s law for line charges. The Attempt at a Solution Basically we used a...
  19. S

    Force Diagram of Electrostatic Forces

    Homework Statement Two uniformly charged spheres are firmly fastened to and electrically insulated from frictionless pucks on an air table. The charge on sphere 2 is three times that on sphere 1. Which force diagram correctly shows the magnitude and direction of the electrostatic forces...
  20. young physical

    Electrostatic force on the particle

    if a charged particle ic located inside a shell of uniform charge there is no net electrostatic force on the particle from the shell. 1st is this fact? 2nd if it is so please explane it to because there is some distance between the particle and other chargeds in shell every one has different...
  21. K

    Electrostatic Equilibrium on the x-axis

    Question - Three charges lie along the x acis as shown below. The negative charge q1 = 25 uC is at x = 2.0 m, the negative charge q2 = 6.0 uC is at the origin. Where must a positive charge q3 be placed on the x-axis such that the resultant force on it is zero? Answer - I was thinking the...
  22. L

    Motion under repulsive electrostatic force

    Is there a simple curve that 2 particles follow when there's a repulsive electrostatic force - like there is for gravitational forces? I don't know how to solve the differential equation that you get for the motion. Laura
  23. C

    Verifying Electrostatic Charges: Q and q

    I have attempted this problem twice and have one more chance before I get the "red ex" so I thought I'd check my thinking. Two identical conducting spheres, fixed in place, attract each other with an electrostatic force of 0.136 N when their center-to-center separation is 65.0 cm. The...
  24. M

    Several Electrostatic Problems

    1) At the two ends of a pole there are two + charged spheres…one has a charge n times that of the other (nq and q) [I actually have a numerical value for n to use to find my final answer]. Along this pole, of length we will call d, there is another charged sphere which is located at an...
  25. M

    Coulombs Law and electrostatic force

    Identical isolated conducting spheres 1 and 2 have equal charges and are separated by a distance that is large compared with their diameters. The magnitude of the electrostatic force acting on sphere 2 due to sphere 1 is F = 8.9 N. Suppose now that a third identical sphere 3, having an...
  26. E

    How does quantum mechanics affect the classical electrostatic force?

    I read Feynman's quantum electrodynamics, but I do not clearly understand, where quantum mechanics enter. So if clasicaly force in electrostatic field equals F = e^2 /4 pi epsilon 0 r^2. What happens, when quanum mechanics is included. I think that for elementary principle we do need...
  27. G

    Multipole Expansion - Electrostatic Case

    Im having a little problem with this question Not sure where to start but I believe that a 3D taylor series expansion might be useful. Please could someone urgently help me out as it is due in a few hours! Thanks for your time. GM
  28. J

    Electrostatic Influence Machines

    Hi, I've been doing some reading on electrostatic influence machines like this one here called Nicholson's Doubler: [PLAIN]www.coe.ufrj.br/~acmq/nicholson.html[/URL] I was wondering if there is any drag force or back attraction/repulsion torques that the rotating disks would experience...
  29. N

    Griffiths' : Electrostatic Energy

    Griffiths : Electrostatic Energy I'm having a little difficulty in understanding how one arrives at the following expression for electrostatic energy of a continuous charge distribution. W = \frac{\epsilon_o}{2}\int (\vec{E})^2d\tau This result is obtained when the volume of integration...
  30. E

    Negative electrostatic potential energy

    I have an example in my book showing 3 point charges each at the vertices of an equilateral triangle. q1 = +2 microC, q2 = -2 microC, and q3 = +1 microCoulombs. the distance between each is 0.30m. The example calculates the electrostatic potential energy of the charge configuration, obtaining...
  31. E

    Electrostatic Equilibrium: Where to Place a Third Charge?

    "Two charges, q1, and q2, are located at the origin and at (0.50m, 0), respectively. Where on the x-axis must a third charge, q3, of arbitrary sign be placed to be in electrostatic equilibrium if (a) q1 and q2 are like charges of equal magnitude, (b) q1 and q2 are unlike charges of equal...
  32. S

    Equilibrium: Electrostatic force and Gravitational force

    Two identical balls of mass 38 g are suspended from threads of length 1.5 m and carry equal charges of 16 nC as shown in the figure. Assume that θ is so small that its tangent can be replaced by its sine and find the value of x. (picture attached) I know that the sum of all the forces must...
  33. A

    Potential energy and electrostatic forces

    show that the potential energy due to electrostatic forces of uniformly charged sphere of radius R and total charge Q is: 3Q^2/5R i don't even know how to start?? i really don't want to hate physics:frown: :frown: :frown: i was reading through in my textbook and they only gave...
  34. C

    Solving the Electrostatic Conundrum: Brute Force vs Symmetry

    Electrostatic conundrum: How "brute force" and symmetry arg. give different answers! Hello everyone, this is my first post -- and an interesting one (or so I think). **Note to Mods: this is NOT me asking for a solution to a HW type problem -- I know and have the solution already -- rather...
  35. A

    Electrostatic boundary conditions

    Im having trouble following how this is derived: The normal component of the electric field is discontinuous by an amount sigma/epsilon_0 at any boundary (when you cross a continuous surface charge). They talk about taking a little box so that the surface integral E dot da = 1/epsilon_0 * sigma...
  36. K

    Electrostatic equilibrium and Gauss' law

    A conducting spherical shell of ineer radius a and outer radius b carries a net charge Q. A point charge q is placed at the center of this shell. Determine the surface charge densit on (a) the ineer surface of the shell and (b) the outer surface of the shell. I'm not sure of my reasoning...
  37. V

    Electrostatic Force Between Conductor and Insulator

    Hi, I have the following question: An uncharged wooden stick is balance on a pivot so that it can rotate freely. If a charged rod is brought close to one end of the stick, the stick will be... Attracted by the charged rod is the answer. This has got me confused for a while. Here is my...
  38. B

    Electrostatic force on nonlinear charges

    http://www.imagebucket.net/images/bigslowy/physicsproblem.jpg What is the strength of the electrostatic force on the top charge? Answer in units of N. I tried breaking it down into components of Fabx + Fbcx ect. but I still don't get a correct answer. Is there a different approach I...
  39. O

    Be creative electrostatic generator

    Hey! I just got this new electrostatic generator and I wanted to know if any of you guys have any cool experiments I could try. So far I have just managed to zap myself and make my hair stand up. Anyone have any ideas for how to make cool experiments?
  40. D

    Find the magnitude of the electrostatic force

    I am having difficulties with the following problem. I have gotten parts (a) and (b) (my correct answers are shown below), but I cannot figure out how to do part (c). Any help with it would be greatly appreciated. Thanks! ------------ The charges and coordinates of two charged particles...
  41. V

    Electrostatic Equillibrium Question

    Hey, Here is my question: Three identical small Styrofoam balls (m = 2.05 g) are suspended from a fixed point by three nonconducting threads, each with a length of 45.5 cm and with negligible mass. At equilibrium the three balls form an equilateral triangle with sides of 28.4 cm. What is the...
  42. F

    Net electrostatic force : four particles form a square

    I apologize in advance - I am completely clueless about this one. I thought I had it figured out, but it turns out that I think I don't know where to even start. Four particles form a square. The charges are q1 = q4 = Q and q2 = q3 = q. What is Q/q if the net electrostatic force on particles...
  43. E

    Solving an Electrostatic Force Problem

    I'm stuck on the following problem: Point charges of q_1=-12nC are placed at (-4,0) cm and (4,0) cm. Determine the magnitude of the electrostatic force on a third charge of q_2=20nC placed at (0,8) cm. So because of symmetry I figured that the x-components of the forces will cancel each other...
  44. T

    Comparing Electrostatic Potentials of Positive and Negative Charges

    This is more of a general question and not a homework question, just to make it clear. Say two test charges are brought separately, one after the other, into the vicinity of a charge +Q. First test charge +q is brought to point B a distance r from +Q. This charge is removed and a test charge -q...
  45. L

    Electrostatic force and virtual photon exchange

    Hello, although being graduated in physics (but not being an expert on QED) I find myself embarassed in trying to explain in very simple terms how the electrostatic force arise from the exchange of virtual photon. Especially when it comes to actually reduce all calculations to the expected...
  46. M

    Understanding Electrostatic Force: Q&A

    Can someone explain this law to me in simple terms? I know that it is the electrostatic force between 2 charged objects in relation to the quantity and inversly related to the square of distance F=K q1 q2 / d^2 ..but what if you have atoms that are spearated by a certain distance and have...
  47. M

    Finding the net electrostatic force on particle 1, triangle

    Hello everyone, Did I do the 2nd part of this problem correct? Part B. I boxed in the answer, i think it will just be easier by showing you my drawing so here is the picture -> http://img221.imageshack.us/img221/9340/phsyicss9lb.jpg thanks!
  48. R

    Direction and magnitude of the net electrostatic force

    Find the direction and magnitude of the net electrostatic force exerted on the point charge q2 in Figure 19-31. Let q = +1.8 µC and d = 41 cm. Direction ° (from the x-axis, which points to the right) Magnitude N *image of diagram* http://www.webassign.net/walker/19-31.gif
  49. J

    Electrostatic force electroscope

    electroscope A large electroscope is made with “leaves” that are 78-cm-long wires with tiny 24-g spheres at the ends. When charged, nearly all the charge resides on the spheres. If the wires each make a 3.0E1° angle with the vertical (see figure), what total charge Q must have been applied to...
  50. R

    Time as a function of distance? electrostatic force

    time as a function of distance? electrostatic force C = coulombs, Ke = electrostatic constant, d = distance, m = mass of electrons, v = velocity, c = a constant F(d) = (KeC^2)/d E(d) = (KeC^2) * integral (1/d) dd = KeC^2(lnd2 - lnd1) E = 1/2 mv^2 v = sqrt(2E/m) =...
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