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. P

    Ratio of charges in Coulomb's Law problem?

    Just got out of my E&M class lecture about Coulombs Law, I'm having trouble getting off of the ground with an electrostatics question: Question: Three charged particles lie on the x-axis (fig. 1). Particles 1 and 2 are fixed. Particle 3 is free to move, but the electrostatic force on it...
  2. J

    Unanswered Electrostatics Questions: Seeking Answers to Common Misconceptions

    Hello everyone! I've recently been messing around and experimenting with electrostatics and have some questions I can't find answers to. Ok here they are: 1. If I understand this correctly a neutral object is attracted to positive and negatively charged objects. If this is true, why does...
  3. J

    How Do You Calculate the Charge Between Two Asymmetric Cylinders?

    Hey all, I'm trying to calculate the charge that forms on two adjacent and asymetrical cylinders when a voltage is put between them. The figures I was using was something like 1mm radius for one and 10mm radius for the other, a voltage of about 20kV and a separation of a few cm. I thought...
  4. U

    How Does a Dipole Affect the Electric Field Near a Neutral Metallic Sheet?

    here is a problem: if a dipole with charges +/- q is brought near a neutral metallic sheet then what is the electric field near the sheet?
  5. P

    What Happens to Surface Charges When a Grounded Wire Connects to a Metal Shell?

    Suppose you've got a metal sphere of radius R and it is surrounded by a metal spherical shell with inner radius r_a and outer radius r_b. The metal sphere has total charge Q. The first thing i had to calculate was what the induced surface charges are on the shell. That was pretty easy, but they...
  6. A

    Another Electrostatics Problem

    Problem: A metal sphere of radius R carries a total charge Q. What is the force of repulsion between the "northern" hemisphere and the "southern" hemisphere? My book gives a formula for the electrostatic pressure: P = \frac{\sigma ^2}{2\epsilon _0} pushing the surface outwards (and...
  7. A

    Electrostatics surface charge Problems

    Problem: 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 carges q_a and q_b. (a) Find the surface charges \sigma _a, \sigma _b, and \sigma _R. (b)...
  8. B

    Electrostatics charged particle Problems

    1. A charged particle was accelerated from rest by a potential difference of 2.50 x 10^5 V. If the particle reached a maximum speed of 2.90 x 10^4 m/s, what potential difference would be required to accelerate this particle from rest to a velocity of 7.25 x 10^4 m/s? 2. The centers of two...
  9. A

    Electric Field Calculation for Non-uniformly Charged Sphere

    I am having trouble with this problem There is a sphere haveing nonuniform volume charge desnity p=ar where a is constant and r is radial distance from centre of sphere. Radius of sphere is R we have to find electric field at centre of sphere. Thanx
  10. N

    Electrostatics: Calculating Charge on Suspended Spheres

    two small spheres, each with 0.120g, have equal charges placed on them. Each sphere is suspended from the same point by its own silk fibre which are 75.0cm long. The repulsive force between them keep their centres 10.0cm apart. What is the charge on each sphere?
  11. P

    Electrostatic Forces on Charges at Different Locations

    I've got the following problem: 1) We've got a charge -Q at location at the origin and two charges of the same magnitude but opposite sign at (a,0,0) and (0,a,0). Determine the total force on the charge at the origin. 2) We've got the same charge -Q at the origin but now a charge of 2Q at...
  12. quasar987

    Another proof in electrostatics

    In proving \nabla \times \vec{E} = \vec{0} for electrostatic fields, Griffiths switches directly from the equation \iint_{\mathcal{S}}(\nabla \times \vec{E})\cdot d\vec{a} =0 To the conclusion \nabla \times \vec{E} = \vec{0}. As for Gauss's theorem, I am wondering if there is a more...
  13. I

    Books on Electrostatics for IIT Prep

    can anyone suggest me books on electrostatics and electromagnetism at a graduate level as iam preparing for indian institute of technology (iit). it would be a great help for me.
  14. Z

    Problem with Electrostatics

    1. When a piece of cellulose acetate (transparency) is rubbed by stroking it for about 10 to 20 times in one direction and brought towards a piece of rubbed polythene strip, i. state what happens, and ii. explain the observation. 2. Before rubbing a polythene strip with a soft cloth...
  15. S

    How Far Does a Moving Electron Get From a Fixed Electron When It Stops?

    hi. i want to ask one problem about electrostaics. i will be very thankful to u if u post reply about this question. Suppose we have one moving electron ,approaching towards a fixed electron. If they 1mm apart when the moving electron has the velocity of 1000cm/s. How far will be the...
  16. P

    Exploring the Effects of Electrostatic Induction on Neutral Objects

    This is my understanding of induction: If a negatively charged rod is brought near (but not touching) a neutral electroscope, the positive charges will move towards the rod, and the leaves will become negatively charged and repel. If grounded, electrons will exit the electroscope, and the...
  17. P

    What is the distance to the nucleus when the particle's velocity is zero?

    potential = 0 particle of mass m charge q is projected with kinetic energy K at a nucleus mass M charge Q that is at rest. it is shot with 'perfect aim' (along the x axis). find the distance x to the nucleus when dx/dt of particle is zero. i know that F = dK/dt = cqQ/x^2 where c =...
  18. D

    Electrostatics problem, kinda confusing

    Two charges, one -q and one +q are located at x=-a and x=+a, respectively. Use a spreadsheet to plot the electric field along the x asix. Part of this problem is choosing a reasonable range for the plot. How do I go about doing this?
  19. B

    Electrostatics drivng me nuts

    I'm stuck on a Electrostatic problem which I just don't seem to get. The left-hand sphere has a positive charge Q and the right-hand sphere has a negative charge -Q. Charge is distibuted uniformly over each of two spherical volumes with radius . One sphere of charge is centered at the origin...
  20. A

    Electrostatics: suspended spheres

    Two small spheres of mass m are suspended from strings of length L that are connected at a common point. One sphere has charge Q, the other has 2Q. The strings make angles (theta1) and (theta2) with the vertical. (a) How are theta1 and theta2 related? (b) Assume theta1 and theta2 are...
  21. maverick280857

    Puzzler for newbies to electrostatics

    Hi... This problem is not an uncommon one and you might easily encounter it in any book that has challenging problems on this subject. I am throwing it here for newbies to Electrostatics who would like to try their hand at solving a puzzler... If a point charge +q is placed at y = 0 and an...
  22. N

    How Do You Calculate Charge from Electric Field in Electrostatics?

    we meet again .. here ,i have a question about electrostaatics... in a particular experiment, a high voltage is created by charging an isolated metal sphere,the sphere has diameter 42 cm and any charge on its surface may be considered as if it were concentrated at its centre. The air...
  23. T

    What Happens to the Force Between Two Touching Charged Spheres When Separated?

    Two conducting spheres (of the same size), one negatively charged, one positively charged are at a finite distance apart. Magnitude of neg charged sphere < pos charged sphere. When the spheres are brought together and touched, and brought back to initial distance, what is the net force...
  24. R

    Solving Electrostatics Question: Third Charge Placement for Zero Net Force"

    Wow, it's been a long time since I've done any physics, but my sister asked me for help on a question and I am stumped. The problem is: What I remember is since the two charges have different signs, the third charge must be placed outside of the other two. It cannot lie in-between the...
  25. T

    Classical Electrostatics problem

    OK, for fun I was solving a simple electrostatics problem, where a charge q is sitting some distance "x" from a grounded conducting sphere. You can use the method of images for this, giving you an image charge q' located at a distance x' from the center of the sphere. The answer I get is...
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