Electrostatic Definition and 883 Threads

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. S

    Electrostatic force problems, help

    Electrostatic force problems, help urgent! Homework Statement Question: An isolated hollow metal sphere of radius 40 cm carries a charge of -10*10^-6. What is the magnitude of the electric field E (a) in the empty space inside the sphere and (b) 60 cm from the center of the sphere ( no...
  2. M

    Electrostatic problem (point charges)

    Homework Statement http://www.freeimagehosting.net/uploads/3e00ce8695.gif Homework Equations Electric field equation derived from Coloumb's Law (given on the screenshot above). The Attempt at a Solution Solution is given in the form of answer sheet...
  3. V

    Minimum distance & electrostatic potential energy

    An alpha particle (made of 2 protons and 2 neutrons) with initial kinetic energy of 1.20 × 10^-12 J travels directly towards the nucleus of the stationary zinc atom The nucleus of a zinc atom contains 30 protons and 35 neutrons, and has a diameter of 4.00 × 10^-13 cm. The alpha particle slows...
  4. S

    D What is the Missing Step in this Electrostatic Algebra Equation?

    Homework Statement I have a homework question on electrostatic seesaws. My problem is the algebra. Homework Equations I have been following another example and any guidance to help me proceed would be great. 0= (2q Q)/(4πε_o r²)+(q Q)/(4πε_o r²)-m 0= (3q Q)/(4πε_o r²)-m m=(3q...
  5. R

    Superpositions of electrostatic forces

    Homework Statement Three particles P1, P2, and P3 are located at the points (−2.00, −1.00), (0, 2.00), and (3.00, −1.00), respectively. P1 has a charge of 5.00 μC, but the charges of P2 and P3 are unknown. However, the three particles exert no net force on a charged particle that is placed at...
  6. D

    Electrostatic potential of unit charge in vacuum

    Homework Statement I'm having hard time seeing that from this picture: Follows that: \phi(\vect{r})=\frac{q}{4\pi\varepsilon_0}\cdot\frac{1}{|\vec{x}|} The thing that puzzles me isn't the equation but this...
  7. K

    Electrostatic force betwen two ions

    Homework Statement A. Find the electrostatic force between a Na+ ion and a Cl- ion separated by 0.5 nm. B. Would the answer change if the sodium ion were replaced by Li+ and the CL ion by Br-?Explain. Homework Equations I believe you have to use Coulomb's Law...? F=k* [(/q1//q2/)...
  8. B

    Electrostatic force question with coulombs law

    Homework Statement A particle of charge of +4.20 x 10^-6 C is 12.0 cm distant from a second particle of charge of -1.70 x 10^-6 C. Calculate the magnitude of the electrostatic force between the particles. Homework Equations Coulombs law is F = (K*Q1*Q2) / R^2 where k = 8.99*10^9, q1...
  9. H

    Calculating the electrostatic force

    Homework Statement Calculate the (electrostatic) force between a Ca2+ and an O2– ion the centers of which are separated by a distance of 1.25 nm. Homework Equations I know that: Coulomb's Law is F = (k q1 q2)/r2 Attractive Force is F = (k z1e z2e)/r2 where z1 and z2 are the valence...
  10. L

    Electrostatic field and potential of an electric dipole inside a conductor

    Homework Statement Given an electrical dipole of electrical dipole momentum \vec P = p\hat k, centered in 0\hat i + 0\hat j + 0\hat k, find the potential in all the space, where V(\infty ) = 0. If the dipole is now surrounded by a hollow spherical conductor (initially discharged), find the...
  11. D

    Electrostatic charge and law of conservation of energy

    Take a capacitor arrangement...the capacitor having 2 plates which are square shaped. Assuming one of the plates as A and the other as B. If A has been given a static charge, it can be said that the all energy possessed by A can be computed when A is discharged...overall discharging will...
  12. S

    Cantilever switch based on electrostatic force

    Dear all: I am going to design a cantilever switch which is working with electrostatic (capacitive) force. I want to design that. That is to find the dimension and material of that. I was wondering if you could kindly suggest a reference for designing this. Thank you very much.
  13. T

    Simple model of electrostatic trap

    Hey guys, I need some help on my research assignment which was dumped upon me during finals week. Thank you research leader for unloading your anger upon this poor undergrad. Anyways, I'm in a project to construct an electrostatic trap... and to model it in matlab. I figure I should try to do...
  14. I

    What is the Electrostatic Lens Effect in Cathode Ray Oscilloscopes?

    Came across it when I was studying about Cathode ray oscilloscopes, it says that two sets of parallel plates are kept at a high pd with another one of relatively lower pd between them. Then electrons from an electron gun are shot into it. It says that the electrons are focused on the cro's...
  15. H

    Electric field strength before reaching the state of electrostatic equilibrium

    Homework Statement In such a picture, http://i1021.photobucket.com/albums/af335/hectoryx/electrostaticequilibrium_1.jpg Induced charges will emergence on the left and right side of non-perfect conductor B, because the effect of the electric field of conductor A. As is known to all, when...
  16. A

    Electrostatic magnetic-field interaction

    simple eg: negatively charged van de graaff generator top and a magnet. Put magnet near top. Would the magnetic field push the electrons of the charged surface to the sides and deeper into the metallic top?
  17. C

    Ratio of gravitational/repulsive electrostatic force

    Homework Statement Calculate the ratio of the magnitude of the attractive gravitational force to the repulsive electrostatic force between two protons. Homework Equations Mass of proton = M = m = 1.672e-27 kg g = 9.80665m/s2 Q = q = 1.60219e−19 C k = 8.9875e9...
  18. J

    What's Wrong with My Electrostatic Equilibrium Calculation?

    This is from Sadiku's Elements of electromagnetics. I have come to a result but it's different from that of the book. Homework Statement Three identical small spheres of mass m are suspended by threads of negligible masses and equal length l from a common point. A charge Q is divided...
  19. Saladsamurai

    Electrostatic FieldSchey's Notation

    Hey there, I am just seeking some clarification wrt the notation that I have come across for the Electrostatic Field: \mathvf{E}(\mathbf{r})=\frac{1}{4\pi\epsilon_0}\int\int\int_V\frac{\rho(\mathbf{r'})\hat{\mathbf{u}}(\mathbf{r'})}{|\mathbf{r}-\mathbf{r'}|^2}\,dV' So are all of the...
  20. R

    Calculating the Divergence of an Electrostatic Field at the Origin

    Homework Statement The electrostatic field of a point charge q is E=\frac{q}{4 \pi \epsilon r^3} r. Calculate the divergence of E. What happens at the origin? Homework Equations The Attempt at a Solution Well the solution is: \nabla.E= \partialEx/\partialx +...
  21. brainpushups

    How does Lord Kelvin's water drop electrostatic generator work?

    I recently made a small version of Lord Kelvin's "thunderstorm" while I was bored at school one day, and I'm still mystified as to how such a large potential gets generated. I have two hypotheses, but I haven't had a chance to test them yet and I was wondering if anybody knew how the generator...
  22. J

    Electrostatic Potential inside sphere of uniform charge.

    1. Given a sphere of uniform charge Q, radius R: Find an expression for the electrostatic potential V as a function of r for r ≤ R. Prior proof: E= Q(r)/(4πϵ0)r^2 ,for r≤R where Q(r) is the excess charge in the spherical volume of radius r 2. Relevant equation: V = Q/(4πϵ0)r 3. I tried...
  23. J

    Electrostatic Clamps Using Dielectrics

    b]1. Homework Statement [/b] Electrostatic clamps are used for holding workpieces while they are being machined, for holding silicon wafers during electron beam microfabrication, etc. They comprise an insulated conducting plate maintained at a potential of several thousand volts and covered...
  24. H

    The condition for application of electrostatic theory

    In the vicinity of antenna, electric field strength have terms that vary as 1/r, 1/(r^2), and 1/(r^3). The terms varying as 1/(r^3) are called the quasi-electrostatic field which can be analyzed with the theory of electrostatic field. The condition is that the size of interested area is less...
  25. P

    Electrostatic charge distribution questions

    If charge distribution inside sphere is non-uniform, how is distribution on outside of sphere uniform? (Think spherical shell with point charge anywhere inside) And how can a non-uniform surface charge be still equipotential. If there was a strong enough induced charge, wouldn't the behavior...
  26. B

    Where is the Max Electrostatic field?

    Homework Statement Consider 2 charges with value q=3[\muC], situated on the xOy plane at (0;2) and (0;-2) [cm]. Obtain the coordinates on the x-axis (y=0) where the modulo of the electrostatic field is maximum. Homework Equations The Attempt at a Solution I am trying to do this but...
  27. P

    Questions about Electrostatic Fields

    I have two questions: Why is it that the field lines of the electrostatic field do stray one from the other one when abs(E) decreases? Second question: Why is abs(E) bigger in the areas where the equipotentials are squeezed up? Thank you!
  28. L

    What Causes the Negative Sign in Electrostatic Potential Energy Calculations?

    another pretty simple question that i can't see: a 1d harmonic oscillator of mass m carries an electric charge q. a weak uniform, static electric field of magnitude E is applied in the x direction. what is the classical electrostatic potential energy for a point particle at position x...
  29. Q

    Calculate the electrostatic energy of a homogeneously charged sphere

    QUESTION: Calculate the electrostatic energy of a homogeneously charged sphere of Volume V and compare the result with 2 times the electrostatic energy of a homogeneously charged sphere of V/2. SOLUTION: OK, so we have a charge Q which is uniformly distributed within a sphere of...
  30. L

    Electrostatic energy of a dielectric sphere

    1. Find the electrostatic energy of a neoprene sphere or ratio R, charged with Q if: a) Q is uniformly distributed in surface The Attempt at a Solution So, I can calculate the displacement field (so that I can use the expresion U= \int \vec{D}.\vec{E} dV), but only for those points in...
  31. H

    Electrostatic potential problem (got 1/3) correct

    Point charges q1, q2, and q3 are fixed at the vertices of an equilateral triangle whose sides are 2.50 m long. Find the electrostatic potential energy of this system of charges for the following charge values. a.)q1=q2=q3=3.90uC I got the right answer for this one 164mJ...
  32. J

    Electrostatic repulsion formula for plates

    Hey all I read somewhere online that Coulomb's Law only applies to spheres and point charges, and was wondering what formula is used to calculate the force between 2 plates whilst charged the same polarity Also, what is the formula to determine how much voltage is required to maintain a...
  33. O

    Calculating Net Charge on a Metal Sphere with Added Electrons

    Homework Statement A Metal sphere has a charge of +6uC. What is the net charge after 1*10^14 electrons have been placed on it? Homework Equations Single Electron - -1.6*10^-19 The Attempt at a Solution 1st. Convert +6uC to 1.6*10^-6 (is this right?) 2nd...
  34. K

    Help with Conductors in Electrostatic Equilibrium

    Can someone please help me with this problem. I don't even know where to begin after drawing the picture. Two identical conducting spheres each having a radius of 0.500 cm are connected by a light 1.80 m long conducting wire. A charge of 63.0 µC is placed on one of the conductors. Assume the...
  35. A

    Change of variable in electrostatic potential energy.

    Homework Statement Hello everyone i have a problem in visualizing why a a change of variable happens. To evaluate a volume integral. I hope that someone could give me a hint of the reasoning that makes you think in that specific change of variable. Homework Equations See the attachment for...
  36. A

    Electrostatic force on a charge

    i was reading the book of Griffin - introduction to electrodynamics. it is written that the force of charge q on Q is not only depends on the distance b.w them but also the velocity & acceleration of charge q.then i think coloumb'law is incomplete at all. it must include some quantity for...
  37. A

    Electrostatic Problem - finding initial separation of two particles

    Homework Statement One particle has a mass of 3.00 \times 10^{-3} kg and a charge of +8.00 \mu C. A second particle has a mass of 6.00 \times 10^{-3} kg and the same charge. The two particles are initially held in place and then released. The particles fly apart, and when the separation...
  38. L

    Electrostatic induction (can someone check my answer?)

    Homework Statement Three identical metal spheres are supported on three insulating stands.A charge q is given on the first sphere .The first sphere is then momentarily touched with the second sphere and then the second sphere is momentarily touched with the third. Finally the third sphere is...
  39. A

    Calculating Electrostatic Force with Coulomb's Law

    Four point-charges are fixed at the corners of a 3.0m X 4.0m rectangle. The coordinates of the corners and the values of the charges are listed below. q1 = 100 microC (0, 4m), q2 = 36 microC (4m, 3m), q3 = 125 microC (0, 3m) and q4 = 32 microC (0,0). Compute the net electrostatic force acting on...
  40. C

    Establishing an Electrostatic Series: My Confusion

    I'm doing an electrostatics lab and I'm getting a bit confused. The object of the lab is to establish an electrostatic series. First, I must choose a reference material, like plastic wrap. Then I charge this reference material by rubbing it in wool. Now, just by looking at any other...
  41. S

    Gauss Law and Electrostatic Field

    Homework Statement Use Gauss' law and symmetry to find electrostatic as a function of position for an infinite plane of charge. Let the charge lie in the yz-plane and denote the charge per unit area by \rho=\alpha*e^{-abs(x/b)} Homework Equations Q=triple integral of density The Attempt at...
  42. P

    Electrostatic Force: -0.7nC Charge at Origin

    Homework Statement A -0.7nC charge is located at the origin, while a 1.9nC charge is located 3.9 m away along the x-axis and a 0.8nC charge is located -1.7m away along the y-axis. The Coulomb constant is 8.98755*10^9 Nm^2/C^2. Find the magnitude of the electrostatic force on the charge at the...
  43. S

    How to Calculate Net Electrostatic Force in a Square Configuration?

    There are four charges, each with a magnitude of 1.98 μC. Two are positive and two are negative. The charges are fixed to the corners of a 0.288-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. Calculate the magnitude of the...
  44. G

    Electrostatic induction in a conductor

    Two aluminium plates, each 150 x 150mm, were separated by 100mm to create a form of parallel-plate capacitor. A DC voltage of 300 volts was connected across the plates to create a (fairly) linear electric field of approximately 3000 V/m between them. An insulated conductor was bent into a U...
  45. G

    Electrostatic induction in a conductor

    Two aluminium plates, each 150 x 150mm, were separated by 100mm to create a form of parallel-plate capacitor. A DC voltage of 300 volts was connected across the plates to create a (fairly) linear electric field of approximately 3000 V/m between them. An insulated conductor was bent into a U...
  46. K

    How Would Changes in Coulomb's Law Affect Electrostatic Interactions?

    Homework Statement 1)Coulomb's law states that the electric force becomes weaker with increasing distance. Suppose that instead the electric force between two charged particles were independent of distance. In this case, would a charged comb still cause a neutral insulator to become polarized...
  47. M

    Electrostatic force of attraction between two particles

    The homework problem reads as follows: A proton and an electron are held in place on the x axis. The proton is at x=-d, while the electron is at x=+d. They are released simultaneously, and the only force that affects their motions is the electrostatic force of attraction that each applies...
  48. P

    Electrostatic Field concept question

    Homework Statement A ping pong ball covered with a conducting graphite coating has a mass .005 kg and a charge -4 microC. What electric field will exactly balance the weight of the ball? Homework Equations qE = mg The Attempt at a Solution I know how to get the magnitude of the...
  49. P

    Electrostatic Constant Written Funny

    So the electrostatic constant k = 9*10^9, but I've also seen it written in my Fundamentals of Phys book (Resnick) and Wikipedia as k = 1/(4*pi*e0). Why is this? Thanks.
  50. J

    Electrostatic Force: Learn About Its Effects

    electrostatic force! Homework Statement http://img10.imageshack.us/img10/3914/picture0117.jpg Homework Equations The Attempt at a Solution
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