What is Electrostatics: Definition and 675 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. J

    Find the unknown charges q1 and q2

    Homework Statement The geometrical positions of point-like charges and point A situated in the xy-plane in terms of the length parameter a. The vector of electric field E at point A is shown schematically and measured as E = Exi + Eyj (that is, both Ex and Ey are given). If possible, find the...
  2. Swapnil Das

    Reasons for Electrostatic interactions

    Hello. Well, each and everyone of us know that Like Charges repel, while unlike charges attract. That's a normal high school physics fact. But what's the reason for that? Is it just an experimental fact, or even does have theoretical significance? Please do help. Thanks a lot Swapnil Das.
  3. superkraken

    Electric Field Calculation for Coaxial Plates with Holes

    Homework Statement two infinitely large plates are at a distance d from each other .they carry a unifor surface charge of densities X and -X.the plates have round coaxial holes of radius R.with d<<R.find the electric field through the axis of the holes(taking them as circles) as a function of...
  4. C

    Force-neutralizing charge (electrostatics)

    Homework Statement A charge 2Q is placed a distance 'd' from charge 4Q. A third charge 'q' is placed 3m from charge 2Q directly on the line between charges 2Q and 4Q. Find d and q such that the force between charges 2Q and 4Q is equal to 0. Homework Equations Coulomb's law: f = k(|q1q2|)/r2...
  5. P

    Electrostatics problem- two sphere

    Homework Statement A spherical capacitor comprises two thin metal spheres of different radii but with a common centre. The following series of operations is completed: The spheres are mutually connected by an internal wire. The outer sphere is raised to potential +V with respect to ground. The...
  6. jfizzix

    Gravitationally induced electric voltage in conductor

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  7. P

    Three concentric spherical conductors -- Find the potential

    Homework Statement I am not sure whether to put this in the introductory level or advanced. It seems to be relatively introductory in an electromagnetism course. A spherical conductor of radius ##a## carries a charge ##q##. It is situated inside a concentric spherical conducting shell of...
  8. N

    Finding work done using definite integrals

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  9. Idyia

    B Why doesn't the flux through a Gaussian surface change with a change in shape?

    Why doesn't the flux through a Gaussian surface change, when the shape is changed? (while keeping the net charge inside it the same) Flux is the dot product of electric field and surface area, so wouldn't it change if surface area is changed?
  10. N

    Electrostatic potential a a point, the pluses and minuses

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  11. person_random_normal

    Electrostatics - System of parallel plates

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  12. Titan97

    Uncharged capacitor connected to a charged capacitor

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  13. Titan97

    A positive charge kept inside a conducting shell

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  14. Titan97

    A conducting shell kept in a uniform electric field

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  15. A

    Approximations used in solving for the electric field

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  16. L

    Green function in electrostatics

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  17. S

    Question about a boundary-value problem (electrostatics)

    Laplacian for polars: $$\frac{1}{r}\frac{\partial}{\partial r}\left( r\frac{\partial \phi}{\partial r}\right) + \frac{1}{r^{2}}\frac{\partial^{2} \phi}{\partial \theta^{2}} = 0$$ This is in relation to a problem relating to a potential determined by the presence of a wedge shaped metallic...
  18. Teameister

    Work done moving charge near a line of charge

    Homework Statement How much work (in J) is required to bring a charge of 2 microC from the point {2*6.8,-7,2*1.1}cm via the point {10,20,1}cm to the point {-3*6.8,3.4,-3*1.1}cm, in a medium with relative permittivity of 3.7, near a line charge along x=6.8 cm, z=1.1 cm, with charge density +329...
  19. F

    Calculate the charge of a density distributed along z axis?

    Homework Statement How do I find the total charge from a material with a charge density given by \rho =10^{-9} \text{cos}\left ( \frac{z}{z_0}\right ) C/m^3 that exist between \frac{-\pi}{3}z_0<z<\frac{\pi}{3}z_0. Homework Equations None I can think of. The Attempt at a Solution Attempt #1...
  20. Titan97

    Three protons and two positrons....

    Homework Statement There protons are and two positrons are held such that two protons are on the ends of a diagonal of a square and the two positrons are on the ends of the second diagonal. The third proton is situated at the centre of the square. The system is released from rest. Find the...
  21. hawkeye1029

    Electrostatics and nuclear force problem

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  22. C

    Why does a charged Styrofoam plate attract paper but repel aluminum foil?

    Homework Statement Based on a lab we did at school, we charged a Styrofoam plate by rubbing it against wool and determined that it attracted pieces of paper but repelled pieces of aluminum foil. Can anyone clarify why this is because I believe that both the pieces of paper and aluminum foil are...
  23. BenR

    Field of variable charge distribution over all space

    Homework Statement A charge distribution has uniform density in the x-y directions and varies with z according to: ρ(z) = ρ0e−|z|/t where ρ0 and t are constants. (a) Find the potential V (z) and the electric field E(z) (b) Sketch them clearly showing their behaviors in the regions |z| ≪ t...
  24. K

    Maximum Torque in Dipoles (electrostatics)

    In a --specifically uniform electric field-- (I may be wrong here) my understanding is that the dipoles will result in no net dipole force (due to cancelling out) but there will actually be a net torque experienced about the center. This torque will be trying to turn the dipole so the moment, p...
  25. X

    Why Does the Force Between Two Charged Objects Change After Contact?

    I was wondering if you could help me explain a physics problem. The topic is Electrostatics: We have two objects that attract each other and the distance between them is r and the force is F1. Then we put those two objects together and then put them back to the same distance as before (r). Why...
  26. V

    Please help me with this doubt from electrostatics

    in deriving the capacitance of a parallel plate capacitor why do we take the field between the capacitors as σ/∈ and not 2σ/∈,when there are two plates and in the region between the capacitors, field must add up so shouldn't it be 2σ/∈?
  27. V

    Understanding Electrostatics: Calculating Potential of Metal Spheres

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  28. V

    Why Isn't Induced Charge Shown in Electrostatics Problems?

    Homework Statement Please see this illustration http://www.physicsgalaxy.com/lectures/1/57/1006/Solved-Example-1#6 (see question only) Homework Equations potential due to a hollow sphere at it's centre = kq/rThe Attempt at a Solution here won't there be an induced positive charge on the outer...
  29. Y

    Work done in electrostatics

    Homework Statement A metallic sphere is placed inside a hollow spherical shell. The potential on the inner and outer spheres is 10 V and 5 V respectively. What is the potential at the center?(The spheres are concentric.) Homework Equations $$V =\frac{kq}{r}$$ The Attempt at a Solution The...
  30. P

    Electrostatics -- the case of a charged cylinder

    Hello , I post a message because I will need help with this exercise I would like to knowif my answer are good, I'm french : An infinite hollow cylinder charge is constituted of a sheath whose outer limits are R2 and R3. Wearing a uniform charge density ρ Question 2)calculate the total...
  31. J

    Electric field from spherical charge distribution

    Hello. I have a problem calculating the electric field from spherical charge distribution. The exercise is: 1. Homework Statement Homework Equations To solve the problem for $$ 0\le R < a$$ i tried 2 ways: $$ \vec{E} = \frac{\vec{a_R}}{4\pi\epsilon_0}\int_v\frac{1} {R^2}\rho dv $$ and the...
  32. C

    Electrostatics || A cone charged unifomly, find intensity

    Homework Statement A cone of height H and base radius A is charged with charge Q uniformly distributed in all its volume. Find electrostatic field intensity at the top of the cone. DATA: H, A, Q Homework Equations E=ρ/(4πε0) ∫Ω dΩ/R2) and R is a vector (rr^+zz^) r^ and z^ are versors The...
  33. Titan97

    Finding pressure on a dielectric between a capacitor

    Homework Statement A parallel plate capacitor was lowered into water in a horizontal position, with water filling up the gap between the plates (gap d=1.0mm). Then, a constant voltage V=200volt is applied to the capacitor. Find the increment of pressure in the water between the gap. Homework...
  34. Titan97

    Derivation of induced charge on a dielectric

    Homework Statement Show the the induced charge density on a dielectric placed inside a capacitor is given by $$\frac{k-1}{k}\sigma$$ where ##\sigma## is the charge density of the capacitor plates and ##k## is the dielectric constant. Homework Equations $$E=\frac{E_0}{k}$$ The Attempt at a...
  35. Titan97

    Capacitor problem from Irodov (3.122)

    Homework Statement What charges will flow after shorting of the switch (Sw) in the circuit below through sections 1 and 2 in the direction indicated by the arrows? Homework Equations Kirchoff's laws The Attempt at a Solution Initially, both capacitors will have a charge of...
  36. G

    Force between charged and neutral sphere after scaling

    Homework Statement Consider two solid dielectric spheres of radius ##a## separated by a dis- tance ##R## (##R\gg a##). One of the spheres has a charge ##q## and the other is neutral. We scale up the linear dimensions of the system by a factor of two. How much charge should reside on the first...
  37. Titan97

    Electric field due to point charge on an infinite metal plat

    If there is a small object with positive charge placed above a metal plate, the object induces a negative charge on the surface of the plate facing the object. Let's call this surface as S1. (The metal plate is initially uncharged). But from conservation of charge, the net charge in a metal...
  38. amind

    Charge distribution on the surfaces of parallel conducting s

    Problem: Consider two parallel and large sheets with a surface area . One has a charge and the other is uncharged. q | | | | | | | | | | What would be the electric fields on the three regions as divided by the sheets ? General solution to problems like as told...
  39. Titan97

    Electric field at center of charged hemispherical shell

    Homework Statement Find Electric field at center of charged hemispherical shell Homework Equations In spherical coordinates, $$dA=R^2\sin\phi d\phi d\theta$$ The Attempt at a Solution From the image, Enet=2dEy=2dEcosφ $$dE=\frac{kdq}{R^2}E$$ $$dE=\frac{k\sigma dA}{R^2}$$ $$dE=\frac{k\sigma...
  40. Titan97

    Finding flux from electric field

    Homework Statement If ##\vec{E}=k\frac{x\hat i +y\hat j}{x^2+y^2}##, find flux through a sphere of radius R centered at origin. Homework Equations ##\int E.da=\int(\nabla\cdot E)\cdot da## The Attempt at a Solution I was able to solve this problem without finding divergence of electric field...
  41. N

    Capacitors in a series circuit W/ one dielectric

    Problem: When a dielectric slab is inserted between the plates of one of the two identical capacitors in Fig. 25-23, do the following properties of that capacitor increase, decrease, or remain the same: (a) capacitance, (b) charge, (c) potential difference (d) How about the same properties of...
  42. A

    Simple question on Laplace's Equation (electrostatics)

    Homework Statement Consider solutions to the One Dimensional Laplace's Equation in Cartesian Coordinates Let the range of x be from x1 to x2 (x1 > x2) and the boundary conditions are V[x1] = V1 and V[x2] = V2 Find the equation for V[x] Homework Equations V[x] = 1/2 (V(x+a)+V(x-a)) V[x] = mx...
  43. S

    Point Charge Repulsion from Spherical Conductor?

    Homework Statement A point charge e is braught near a spherical conductor of radius "a" having a charge "q".show that the particle will be repelled by the sphere unless its distance from the nearest point of its surface is less than (a/2) *√(e/q) approximately? Homework EquationsThe Attempt at...
  44. C

    Electric Field Between Three Point Charges

    Homework Statement 1. Compute the electric field vector at the position of charge B for the case where q_{A}=4q_{C} and r_{1}=2r_{2} 2. Suppose that all three charge are positive and that q_{A}=4q_{C} . Consider the case where f q_{B} is moved to the right by a distance dr. Now r_{1} = 2r+dr...
  45. not_waving

    Electric field of a sphere in a point A

    My first homework for electrostatics course I'm taking is to find the vector of electric field of a completely hollow sphere (radius r, surface charge density σ in a point A, by integrating the electric field through the whole sphere. I already figured out the electric field of a ring in a point...
  46. C

    A positively charged wire bent into a semi-circle

    Homework Statement A positively charged wire is bent into a semicircle of radius R, as shown in the figure below. The total charge on the semicircle is Q . However, the charge per unit length along the semicircle is non-uniform and given by λ=λocos(θ) What is the relationship between λo, R...
  47. C

    Calculating Electrostatic Force on a Suspended Gossamer Spider

    Homework Statement You are studying Gossamer Spiders in a biology research lab and marvel at their ballooning stunts. These Spiders disperse by spinning strands of silk in open air. The flight of these spiders is electrostatic in nature because everything that moves through air develops static...
  48. C

    Electrostatics Deflection Problem

    Homework Statement In inkjet printing, a rapidly moving nozzle horizontally squirts drops of ink that form letters and images on paper. A common problem is horizontal white lines running through the print due to a clogged nozzle. Another common problem is paper dust. (a) Within the context of...
  49. SquidgyGuff

    Stoke's and Gauss's Theorum in proving div(curlA)=0

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  50. SquidgyGuff

    Calcularing area vector using line integral

    Homework Statement A closed curve C is described by the following equations in a Cartesian coordinate system: where the parameter t runs monotonically from 0 to 2π, thus defining the direction of C. Calculate the area vector of the planar region enclosed by C, using the formula: 2. The...
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