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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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...
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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...
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The problem puts forth and identity for me to prove: or . It says that I can use "straight-forward" calculation to solve this using the definition of nabla or I can use Gauss's and Stoke's Theorum on an example in which I have a solid 3D shape nearly cut in two by a curve...
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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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Essentially it gives the potential above the xy-plane as and I am tasked with verifying it satisfies laplace's equation, determining the electric field, and describing the charge distribution on the plane.
Homework Equations
then
The Attempt at a Solution
As far as I...
I need some book on Electrostatics. I don't have knowledge in this field so I need something "beginner friendly", I mean it should cover this subject from very beginning.
Thanks in advance.
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Four equal point charges q = +22.4 μC sit at each corner of a square. What charge Q, in μC, must be placed in the center so all the charges are in equilibrium? Your answer must include the sign of the charge.
Homework Equations
F = q1*q2 * k / r^2
3. The Attempt at a...
If we have two negatively charged bodies , say A and B, and body A has more electrons on its surface than Body B , would the electrons of body A transfer to body B?
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Three charged particles are placed at each of three corners of an equilateral triangle whose sides are of length 2.7 cm . Two of the particles have a negative charge: q1 = -6.0 nC and q2 = -12.0 nC. The remaining particle has a positive charge, q3= 8.0 nC . What is the net...
I was just wondering why the strength of the electric fields of insulating surface charges like sheets and shells aren't dependent on the distance from the charge according to Gauss's Law?
Six mercury drops of equal size given potential of +3v and two other drops are given -3v potential. If they coalesce what is final potential
This question had been eating my brain i know solution if they are given same potential but what to do when they have different potential
Given a system of two charges (+7q and -q) some of the field lines will terminate at -q while others go on towards infinity. I've read that the portion of the field lines that terminate is given by (1/7), but I have no idea why that is. I am supposed to find the maxium angle of a field line...
Ok we know that the electric field(uniform or non uniform) is a conservative field.
Imagine three horizontal electric field lines in '+X' direction separated by unequal distances let's say line 1 and 2 is separated by distance 'a' and line 2 and 3 is separted by some distance 'b' such that...
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Spherical capacitor with two linear and uniform dielectrics with relative permitivitty Ɛr1 and Ɛr2 is connected to constant voltage U. When second dielectric is removed, intensity of electric field by inner electrode is reduced by 1/3, and electric field by outer electrode...
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Hollow dielectric cylinder, with inner radius a, outer radius b, and height 2h is uniformly polarized by volume. Polarization vector is normal on the bases of a cylinder. Intensity of polarization vector is given, P. The surrounding area is vacuum. Calculate intensity of...
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A conducting sphere of radius a is surrounded by a neutral conducting shell of radius b (b > a).Connections are provided as shown in diagram. Initially, the sphere has a charge Q. The switch S1 is opened and then closed. The switch S2 is then opened and closed. Finally, the...
Homework Statement
Given a situation like this:
Where the two blocks are perfectly conducting materials and are touching, will they separate? If they do separate, will they have the net charge values you calculate in the initial setup using Gauss's Law?
There are no numbers, it's just...
Our teacher derived an expression for electric field due to thin sheet using gauss law which was sigma/2*epsilon naught which was independent of r but dies that mean the field will be same even if r is 10000km but field is also equal to kq/r^2
Hello, so this was a past assignment question that I attempted. I got the right answer but in an incorrect way (I guess my thinking was not based on the concept?)
1. Homework Statement
Three point charges of charge Q = 10...
I originally posted the following question on physics.stackexchange, but no one was able to answer it. I did find this answer on PhysicsForums, but I was already aware of the oscillation of electrons in response to an external electric field.
What is the physical cause behind a material having...
Hi... I want to know why charge density is higher at sharp points in a conductor? I have gone through the analogy of two spheres connected by a wire... But is there any other explanation which is not specific to spheres...?
1. Two small spheres with masses m1 and m2 hang on weightless, insulating threads of length L1 and L2. The two spheres carry charges of q1 and q2 (like charges) respectively. The spheres hang such that they are at the same level with one another. The threads are inclined at angle theta 1 and...
A negatively charged plastic rod will negatively charge a pith ball when in contact. My understanding is that the extra electrons transfer from the rod to the ball, thus giving the pith ball a negative charge.
When an electrophorus is charged and the metal pan is put on top, it doesn't become...
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Plate capacitor with distance between plates 'd=4mm' is fully filled with homogeneous linear dielectric. Capacitor is connected to the source of DC voltage, first stationary state is established, then the capacitor is separated from DC voltage source. After that, dielectric...
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You have a new unknown material. You want to get a rough approximation as to the location of the unknown material on the electrostatic series. You only have two tools at your disposal; some wax and a charge detector. Design an experiment (procedure) that will help you...
Hey, my teacher gave us this scenario and I didn't really understand how he went about doing this. I was wondering if there was someone who could shed some light. Thanks!
You have a new material in front of you titled Material Gamma. You want to get a very rough
approximation as to the...
I'm studying for the physics GRE and am fairly poor with EM.
1. Homework Statement
What is the work needed to assemble four point charges q into a regular tetrahedron of side length a?
Homework Equations
W = 1/2ΣqiV(ri)
The Attempt at a Solution
Assume that the origin is at one of the...
In electrostatics, why is it that identical spheres that are touched for a brief moment or connected by a conducting wire (wire not gaining any charge) should have an equal charge? Why is that they come in an equilibrium of charge?
For example - If we take 2 identical spheres one bearing a...
Hi! I have trouble with solving this problem and would be really thankful for some help. :)
1. Homework Statement
Inside a thin, spherical metal-shell with a radius of 50 cm, a smaller homogenous metal-sphere with a radius of 20 cm is placed concentrically. The smal sphere is grounded through...
Homework Statement
This problem is taken from 'Introduction to Electrodynamics' by David Griffiths.
(a) Twelve equal charges, ##q##, are situated at the corners of a regular 12-sided polygon (for instance, one on each numeral of a clock face). What is the net force on a test charge Q at the...
Homework Statement
My Physics course does not give an in-depth overview of electrostatics at all (it is rather shallow, focusing on electronics and circuit analysis). However, I find that I really need to understand it fully to form the basis for magnetism and generation. So... I have a few...
At the moment we are working through problems in Griffiths' Electrodynamics textbook and it got me thinking...
In magnetostatics we have the magnetic vector potential A and in the use of dielectrics problems we have the vector D. Why is it advantageous to use these vectors and not just stick to...
Can anyone please tell me where I am going wrong? I am getting the incorrect answer for the Word Done should be: WD = q(3x^2-6y) ...
Apologies for not changing it into the format on here - but for my revision I have pretty much done that myself.
I recently studied Gauss' theorum according to which there is no electric field inside a closed conductor. But an isolated chage emits field lines in all possible directions. So why is it that there are no electric lines from the surface of the closed conductor inside it?
I heard that maximum electric potential for charged ring is at its circumference. Is there an expression to find the electric potential at any point on the circumference of a charged ring?
Homework Statement
Consider an electron-proton pair and compare its electrostatic force with that of the gravitational force [G=6.67x10^11 Nm^2/kg^2].
Homework Equations
F = k * |q1 * q2| / r^2
k = 1/4π∈
The Attempt at a Solution
I calculated the force by using the charge of an electron...
Imagine an uncharged solid spherical conductor. Inside this spherical conductor, there is a cavity of a weird shape carved out of it. And somewhere inside this cavity, there is a charge +q (or rather, a charge distribution of total charge +q).
The charge +q induces an opposite charge -q on the...
Imagine a surface charge ##\sigma##. The boundary condition on ##E## is
##E_{above}-E_{below}=\frac{\sigma}{\epsilon_0}\hat{n}##, where ##\hat{n}## points outwards perpendicularly to the surface.
Because the field inside a conductor is zero, it requires that the field immediately outside is...
Imagine an uncharged solid spherical conductor. Inside this spherical conductor, there is a cavity of a weird shape carved out of it. And somewhere inside this cavity, there is a charge +q.
The charge +q induces an opposite charge -q on the wall of the cavity of the conductor, which distributes...
Homework Statement
An infinitely long dielectric cylinder with radius R and relative permittivity ##\epsilon_r## contains a free charge density given by:
##\rho(s)= ks## for s<R and 0 for s>R, where k is a constant.
Find the polarization P and any volume or surface polarization charge...
For a research project, I have to take multiple derivatives of a Yukawa potential, e.g.
## \partial_i \partial_j ( \frac{e^{-m r}}{r} ) ##
or another example is
## \partial_i \partial_j \partial_k \partial_\ell ( e^{-mr} ) ##
I know that, at least in the first example above, there will be a...
1. Prove, without using Gauss's law, that the field inside an infinitely long, uniformly charged cylinder is zero.2. Electric field of a charged surface3. My lead is that from a given point, I draw a very narrow cone to any piece of area on the cylinder, with distance r away.. That creates a...
Homework Statement
An infinite solid cylinder of radius A and uniform charge distribution ρ is surrounded by a thin cylindrical envelope of radius B and linear charge distribution λ. The two cylinders are co-axial.
Find the potential V(r) as a function of r from r=0 to r=∞.
Homework Equations...
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The total electric flux from a cubical box 34.0 cm on a side is 1.29 x 103 N·m2/C. What charge is enclosed by the box?
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Three charged particles are placed at the corners of an equilateral triangle of side d = 1.00 m (Fig. 16-53). The charges are Q1 = +4.0 µC, Q2...
Homework Statement
Two small plastic balls hang from threads of negligible mass. Each ball has a mass of
0.14 g and a charge of magnitude q. The balls are attracted to each other and the threads attached to the balls make an angle of 20.0 degree. with the vertical. The balls are 2.05 cm apart...
Homework Statement
Three positive particles of charges 11 μC are located at the corners of an equilateral triangle of side 15.0 cm. Calculate the magnitude and direction of the net force on each particle.
Homework Equations
Coulomb's Law
The Attempt at a Solution
I think, that this is easy...
A negative charge cloud distribute as a ellipsoid and a positive point charge situated at the centre of the ellipsoid.What should be the dipole moment of charge distribution.I mean, if the negative charge distribution is spherical and positive point charge at the centre then surely dipole moment...
Hi, could someone tell me why you get a shock from contact with a conductor when you are charged and not from an insulator. As I understand it, if you become charged by friction then you have an excess of charge. Let's say I have gained electrons from another material I have rubbed against. If I...