What is Electrostatics: Definition and 679 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. Peeter

    Fourier transform solution to electrostatics Poisson equation?

    Am just playing around, and following examples of Fourier transform solutions of the heat equation, tried the same thing for the electrostatics Poisson equation \nabla^2 \phi &= -\rho/\epsilon_0 \\ With Fourier transform pairs \begin{align*} \hat{f}(\mathbf{k}) &= \frac{1}{(\sqrt{2\pi})^3}...
  2. 9

    Charging by Contact: Calculating Charge on a Sphere after Multiple Contacts

    Electrostatics question, need help urgent! Homework Statement A small metal sphere carrying a charge of -2Q is first brought into contact with sphere R Which has a charge of +Q, and then into contact with sphere S which has a charge of +2Q, and finally into contact with sphere T which has a...
  3. S

    Coulomb's Law - Electrostatics

    Hey. I only just started this unit at school (after coming back from holidays and forgetting everything!) and I'm having trouble with the following problem: Homework Statement "Four point charges A, B, C and D are arranged on the corners of a square of side 25cm. If A and B each have...
  4. A

    One-dimensional lattice (electrostatics)

    Homework Statement Hey guys. So, I got this question in the pic. First of all, I drew what I think to be a one-dimensional lattice (in the green box) but I'm not sure, is it right? Second of all, I don't really understand the question, I mean I know that a potential energy of charge q is...
  5. A

    What are the equations and solution for electrostatics?

    Homework Statement Hey guys. Is it correct what I did there? Thanks in advance. Homework Equations The Attempt at a Solution
  6. J

    Is Gauss' Law Accurate for Point Charge Divergence in Electrostatics?

    I've "derived" the first Maxwell equation of the divergence of the E-field starting at the Coulomb force of a point charge using Gauss law and even the Dirac delta function to justify the divergence at the origin. Now I'm wondering: when you state the law in differential form, i.e. not...
  7. M

    Does Electric Field Depend Solely on Internal Charges?

    Can someone please check my answers and explain if I get any wrong? 1. A point charge +Q is inside an uncharged conducting spherical shell that in turn is near several isolated point charges, as shown above. The electric field at point P inside the shell depends on the magnitude of (A) Q...
  8. I

    Electrostatics - Magnitude and direction of electric force

    Homework Statement What are the magnitude and direction of the electric force on the +2.0x10^-6 charge shown in the diagram (included in the attachment)? Homework Equations F = kq1q2/r^2 The Attempt at a Solution I used the Ep = kq1q2/r^2 equation and plugged in the numbers but...
  9. I

    What is the applied voltage V?

    Homework Statement An object with a charge of +4.0 x 10^-18 C and a mass of 1.1 x 10^-15 kg is held stationary by balanced gravitational and electric forces midway between horizontal charged plates. What is the applied voltage V? Homework Equations The Attempt at a Solution I...
  10. I

    Electrostatics and potential question

    Homework Statement A 2.5C charge is moved from a point with a potential of 12V to another point of potential 75V. How much work was done on this charge? Homework Equations ΔV = ΔEp/Q The Attempt at a Solution I am unsure how to do this question but what I did do is I took the two...
  11. S

    Why separation of variables? (electrostatics)

    "A sphere of homogeneous linear dielectric material is palcced in an otherwise uniform electric field E. Find the electric field inside the sphere." Griffiths uses separation of variables to solve laplace's equation in the interior of the sphere. I have two questions. (1) How can you try...
  12. B

    Electrostatics Multiple Choice Questions

    I bolded the answer I think is correct - I'm just a little unsure on these, any help would be appreciated! 1. A capacitor and resistor are connected in a series with a batter and a switch. The instant after the switch is closed A. the voltage across the resistor is equal to the emf of the...
  13. T

    Electrostatics charge density

    Homework Statement I didn't know how to display a lot of the symbols, so I wrote the problem out in microsoft word, took a screenshot, uploaded it to photobucket, and linked it. Basically, I have to find the charge density as a function of r given the electrostatic field in the image. Any...
  14. X

    How Can I Solve Complex Electrostatics Problems?

    pls help me solve the attached problems.. The comments would be appreciated. Thanks in advance.
  15. H

    Electrostatics - Charge Density

    Hi, if we only have an electrostatic potential given. How to calculate the charge density? I know of course Maxwell equation, here without any time dependence, but I missed always some further specifications, or I forget something important :confused: :redface: thanks greetings
  16. R

    Electrostatics - force on point charges by electric field

    Homework Statement A square, with each corner as a point charge, A, B, C, and D. They all have the same charge of 5.0 x 10 ^(-6) C. Length of each side of the square is 0.1 m. 2 negative charges diagonal from each other, and the other two are positive, diagonal from each other. Question asks...
  17. alexmahone

    Physics olympiad - electrostatics

    (Any number of options may be correct.) Three concentric spherical shells have radii r, 2r and 3r with charges q1, q2 and q3 respectively. Innermost and outermost shells are earthed. Then, (a) q1+q3=-q2 (b) q1=-q2/4 (c) q3/q1=3 (d) q3/q2=-1/3 The answer key tells me that (a), (b)...
  18. P

    Electrostatics, electric fields and electric potential

    THe following is a homework assignment from AP Physics. Homework Statement Two large, flat parallel conducting plates are .10m apart. THe lower plate has a Voltage of 10v while the upper plate has a voltage of 20V. Point P is located .04m from the bottom plate. Find: a) THe magnitude of the...
  19. L

    Is the Potential Zero Inside a Grounded Inner Sphere?

    Hello, I have my first exam tomorrow in Electricity & Magnetism and I really need to know whether I solved this question correct or not, and I do not own the answer key to the book which I took the question from. Thanks in advance! Note: English is not my mother-tongue and neither do I study...
  20. D

    Electrostatics - Charged ball tied to a ceiling

    a ball with a mass of 100g is tied to a ceiling on a 1m cord and is charged with a positive charge of 3*10^16 c, what angle will the cord lift to if it is placed next to an infinite board charged with a density of 5*10-6 c/m^2 (positive), the board is placed at a constant angle of 45 degrees to...
  21. zimo

    Electrostatics Problem: Find E Field and R

    Homework Statement The problem is attached as an image. Homework Equations R=integral(rho*D/A) I guess that there is more... The Attempt at a Solution I got stuck stright on A), for I don't have a clue what to do with such a weird Rho value. Afterwords when we want to find E...
  22. R

    Electrostatics: a question regarding a charged insulated sphere

    the question that i have encountered was: "given an insulated charged sphere, what is the force applied by one half of the sphere on the other half?" i have tried calculating the integral but it seemed a little too complicated for me (plus i am not absolutely confident what the correct...
  23. R

    Can Electric Forces Repel and Attract Unlike Gravitational Forces?

    Homework Statement I have a series of about a dozen questions, my son is taking a course that was outlined by his school " as a great way to get ready for Grade 12" it is mostly multiple choice so if someone could help us choose the right answer with a little bit of an explanation. He has done...
  24. S

    How Does Charge Placement Affect Electric Potential and Potential Energy?

    This question is similar to the one that I posted previously: Two point charges each of magnitude 2.09 micro Coulombs, are located on the x-axis. One is at x=1.38 m and the other is at x=-1.38 m. a) Determine the electric potential on the y-axis at y=0.511 m. b) Calculate the electric...
  25. S

    How Do You Calculate Electric Fields and Forces Between Multiple Point Charges?

    I could really use some help with the following question: Three point charges are located as follows: q1= (0,0) m, q2= (0,-0.120) m, q3= (0.272,0) m. Take q1= 4.37 x 10-9 C, q2= -3.00 x 10-9 C, q3= 6.41 x 10-9 C. a) Find the vector electric field that the q2 and q3 charges together create...
  26. gulfcoastfella

    Coursework question: Poisson's Equation for Electrostatics

    Homework Statement (This isn't a homework problem; I'm just working through Griffiths' "Introduction to Electrodynamics" textbook, and can't find a very clear explanation.) When the relationship between electric field and charge distribution are given by: \nabla \cdot E =...
  27. Z

    Electrostatics BVP with Poissons

    Homework Statement http://stashbox.org/138351/Image-24.png http://shup.com/Shup/45816/Image-25.png Homework Equations The Attempt at a Solution As you can see, this is an example problem from my text. I'm looking for some clarification in their decision to assume potential...
  28. 1

    Electrostatics - Calculate the repelling force of a charge q

    Homework Statement It is given a hemisperical shell charged uniformally with a density charge equal to s. Calculate the force by which it repels an electric charge q which is put in its center(in the center of the largest diameter).
  29. D

    How Close Will an Alpha Particle Get to a Gold Nucleus?

    [SOLVED] Electrostatics Problem I've been trying to solve this problem for the longest time, but it doesn't seem to give enough information. Homework Statement If an alpha particle is fired straight at a nucleus of a gold atom, (q = 79 e) at a velocity of 3.3 x 10^4 m/s, how close will it get...
  30. C

    Electrostatics and electric charge and field

    Homework Statement A charged sphere is suspended by a nonconductive string in a uniform horizontal electric field. The electric field exerts a force on the sphere such that its equilibrium position is diplaced at an angle  = 30° relative to the vertical, as shown in the diagram below. The...
  31. N

    Electrostatics: Potential of +28.0 nC Sphere in Vacuum

    A 2.00 mm diameter conducting sphere in vacuum is charged with +28.0 nC. Determine the potential at a distance of 1.70 m from its center. [Hint: Since 1.70 m >> 2.00 mm this is essentially a point-charge.]
  32. D

    Electrostatics with 2 charged masses on string help?

    Homework Statement Two identical spheres having the same mass, m = 0.60 kg and the same positive charge, q, are suspended from the same point by strings of length 20.0 cm: (a) What charge q resides on each sphere? (b) The apparatus above is now placed in an upward directed but...
  33. S

    Three Kind of electrostatics problem(quite )

    Three Kind of electrostatics problem(quite urgent) Homework Statement The first kind of prbolem is about the dielectric coefficient http://myweb.polyu.edu.hk/~07190086d/phy/q1.zip I know the equations below but I don't know how to relate the E-field into eqn1 The main reason is that I...
  34. R

    How do conductors and insulators behave in an electric field?

    So, I believe I've got the math part down but, I'm having trouble understanding the theory. Can someone briefly explain how conductors work? Grounding? Insulators? Direction of electron flow. Induction? Conduction? Anything else would be great, thanks.
  35. J

    Calculating D from ρv = 2sinФ + cosФ (c/m^2) in Electrostatics

    electrostatics question! hello all... can anybody helps... If ρv=2sinФ+cosФ(c/m^2) find D?!
  36. P

    Electrostatics, ONE TEENSY little problemo please HELPPPPP thanks

    [SOLVED] electrostatics, ONE TEENSY little problemo! please HELPPPPP thanks! Homework Statement Two charges of q1 = 1.3 µC and q2 = -2.6 µC are d = 0.60 m apart at two vertices of an equilateral triangle as in Figure P16.56. (d) What is the work required to move a 3.2 µC charge...
  37. E

    [Electrostatics] Flux Problem,

    Electrostatics Flux Problem Homework Statement A linear charge rho L = 2.0 uC lies on the y-z plane. Find the electric flux passing through the plane extending from 0 to 1.0m in the x direction and from -infinity to infinity in the y direction. Homework Equations Alright, so the formula...
  38. M

    Electrostatics: Conducting Sphere in Uniform Electric Field

    Homework Statement A small conducting sphere of mass M is attached to a string of length L. It is at rest in a uniform electrical field of magnitude E directed due right. The sphere has a charge of Q and the string makes a 30 degree angle with the electric field. a. Calculate the...
  39. J

    Electrostatics - Negative charge in sphere

    Homework Statement a metal grounded sphere of radius R in vacuum has a negative charge inside at a distance a from the centre. a) Draw the e-field in the sphere, b) find the force on the charge, c) and determine the maximal and minimal surface charge density, d) as well as the magnitude of the...
  40. R

    Where is the neutral point? Electrostatics

    Homework Statement At the neutral point the electric field intensity is zero. Two point charges q1=+2nC and q2=-3nC are separated by 2.0m in air. Where is the neutral point?Homework Equations E=f/q coloumbs law E=E[q1] + E[q2] The Attempt at a Solution i don't have a solution for now since i...
  41. A

    Solving Electrostatics Problems: Contact of Neutral & Charged Spheres

    Hi, i have been assigned a series of problems that basically follow the same pattern, but I am unable to solve the first one which is making it difficult to solve the others. here it is An insulated metal sphere (X), that has no net charge (neutral), is brought into contact with a similar...
  42. J

    Calculating Q for Cylinder with Inhomogeneous E Field

    [SOLVED] simple electrostatics problem Homework Statement a cylinder, the inhomogenous E field is given by E = E_{0} (\frac{r}{R})^{3} the assignment was to calculate Q of a piece of the cylinder of length L in two different ways, by gauss law in integral form and in differential form...
  43. 8

    Elementry Electrostatics question

    Homework Statement Two point charges (q1=+20 nC and q2=-40 nC) are placed 10.0 cm apart onlong the x-axis. Where can a third charge (q3=+20 nC) be placed so that the net electrostatic force on that charge is zero? Homework Equations F=k(q1q2)/r^2 The Attempt at a Solution It's...
  44. E

    Electrostatics conductor problem

    [SOLVED] electrostatics problem Homework Statement Two spherical cavities, of radii a and b, are hollowed out from the interior of a (neutral) conducting sphere of radius R. At the center of each cavity a point charge is placed--call these charges q_a and q_b. Why is it necessarily true...
  45. C

    How Do Conducting Layers Affect the Electrostatic Energy of a Spherical Shell?

    I'll try my best to describe the question, though Enligsh is not my mother-tounge. Hope I'm clear enough! the problem: There's a thick spherical shell made of insulated material (like a thick ring), with an inner radius a and outer radius b. The shell is charged with a changing charge...
  46. Y

    Electrostatics of balls on a string

    Homework Statement In Fig. 21-42 (I attached an MSPaint rendition of it), two tiny conducting balls of identical mass m and Identical charge q hang from non-conducting threads of length L. Assume \theta is so small that tan \theta can be replaced by its approximate equal, sin \theta. (a)...
  47. S

    What career opportunities are available in electrostatics?

    I'm currently a high school senior planning on going to college to study Electrical Engineering. I've become quite fascinated by the topic of electrostatics and so I'm wondering what careers/jobs are there in this field?
  48. R

    How Is Energy Calculated for Four Charges at a Square's Corners?

    What is the energy required to bring four identical charges in from infinity such that they occupy the corners of a square with side length r?
  49. P

    What is the relationship between the angle theta and the charge q?

    please help with this problem...i have No clue how do it Two pith balls of mass m are suspended by silk strings of length L. When they are charged they repel each other at an angle of 2 theta, since like charges repel. Using Coulomb's Law and Newton's Law, derive the following...
  50. F

    Work and Electrostatics - a bit of Clarification, please

    Work and Electrostatics - Help! Homework Statement I need to place equal and oppositve charges on a piano and at the top of a 5.0 meter ramp in order to move a 1000 kg box up a 30 degree frictionless ramp. The box has a charge of +Q and the top has a -Q. A) What magnitude charges do I...
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