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.
EDIT: I'm extremelly sorry, i just noticed the sticky above my post saying not to post homework qustions in the forum.
Dear Physics Forums,
I am a 16 year old high school student currently doing year 11 physics. To do this weekend we were givin an exercise sheet with various questions...
Homework Statement
The problem is a Multiple Choice Question, as follows.
Q: An electron moves with a constant velocity in an electric field. What could its direction of motion be?
1> Parallel To Field's Direction
2> Anti-Parallel To Field's Direction
3> Perpendicular To Field's Direction
4>...
Electrostatics test on Tuesday -- helpless
Hi all,
I have a bit of an awkward problem: it is the end of the year for the
2-year "get your A-levels as an adult"-school I'm currently visiting,
and the only test left is in Electrostatics. Unfortunately Physics is a
major subject and thus you...
if the capacitor plates are of different sizes and it is connected to battery, will even then the two plates get charges of exactly the same magnitude?
Homework Statement
A ping pong ball of mass 3*10^-4 kg is hanging from a light thread 1 m between 2 vertical parallel plates 10 cm apart. When the potential difference across the plate is 420V, the ball comes to equilibrium 1 cm from one side of the original position. What is the tension of...
Hi all,
Recently got to thinking about electrostatics and electron densities and band structures. If you have an electrostatically charged piece of material, say for example, a metal, does the density of states of that metal change because of the depletion of electrons? Alternately, if...
Again I am not ssure what to do.
An electron(mass 9.11x10^-31kg) is accelerated in a uniform E field (E=3.0x10^4 N/C) between two parallel charged plates. The separation of the plates is 1.6cm. The electron is accelrated from rest near the negative plate and passes through a tiny hole in the...
I had this question on the test yesterday,
why does brushing or combing your hair give it "volume"?
my answer was because combing or brushing involve collision (like rubbing) between the particles of different object, making one object to become negatively charg and the pther positively...
A particle having mass m and charge q moves along a line under the action of an electric field E = alpha – beta *x where alpha and beta are positive constants and x is the distance from a point where the particle was initially at rest. Then, for an observer moving with acceleration q*alpha/m...
Well,I think this is interesting.I invite people to think over it.
consider a charged spherical shell.Throughout its interior,E=0.
Now,consider the centre.From Laplace's equation and Earnshaw's theorem,this point is not a point of potential minimum.So,a charge at this point cannot be in stable...
Homework Statement
A line charge has density λ and extends along the x-axis from -a to +a. Find the electric potential at a point r on the x-axis (r>a). Use your result to find the E-field at r.Homework Equations
V = \frac{1}{4\pi \epsilon _0}\int\frac{dq}{r} The Attempt at a Solution
I've said...
Can someone say why it is said that in electrostatics,the test charge may be moving very slowly?Specifically,what is wrong if the test charge moves at a speed which is a significant proper fraction of speed of light?
Homework Statement
3 balls are on a ?string?/line?. Each are equally displaced, 72cm. Ball A has a charge of -50e5c, Ball B a charge of +25e2, Ball C -10e10.
1. What is the net force applied on the middle ball (Ball B)?
2. Assuming a force to the right(ungiven name of Ball D?) (of Ball C)...
Homework Statement
2 small spheres each having a mass of 0.1g are suspended from the same point on silk threads 20cm long. When given equal charges, they repel, resting 24cm apart. Calculate charge of each.
Homework Equations
F(w)=mg(a)
F=kQ(1)Q(2)/d^2
k=8.987x10^9 N*m^2 / c^2
The...
I have a problem in electrostatics in which there is a uniformly charges semi-sphere of radius a with its base in the xy-plane and I want to find the electricfiled at some point h on the z-axis. What I am having trouble with is that how do you specify the vector that goes from an infinitesimal...
From Griffiths, Third edition Intro Electrodynamics
I've been working on this problem, and I get 2 different answers. I get the same answer for parts b and c, but not for a. I know I'm probably just doing something silly along the way, but I can't find my mistake...
Homework Statement...
Homework Statement
1) From the observation that there's an electrostatic attraction between object A and B, what's the most you can conclude about the electric charge on A and B?
2) A plastic sphere with a positive charge of 4.8E-19 C is held stationary in a gravitational field of strength...
Homework Statement
What is the radius of the orbit of an electron traveling at 9.0E6 m/s around a zinc nucleus(which contains 30 protons)?
Homework Equations
F=(kQq)/r^2
F=QE
ac=v^2/r
Fnet=ma
The Attempt at a Solution
30 protons x 1.6E-19 = 4.8E-18 C
electron - 1.6E-19 C
F=ma...
Here's the problem:
The passage of a thundercloud overhead caused the vertical electric field strength in the atmosphere, measured at the ground, to rise to 0.1 statvolt/cm [E_0].
(a) How much charge didthe thundercloud contain, in esu per cm^2 of horizontal area?
(b) Suppose there was...
Homework Statement
how to use coulomb's law to find the r value of the three points when the total distance is 50 cm
Homework Equations
f=Kqq/r^2
The Attempt at a Solution
i assumed that is it was uniform and sais r1+r2=r3 but now i think that is wrong
Homework Statement
Calculate the magnitude of the field strength at point P as shown. The distance between the centers of the 1.5E-6 C and the 9.2E-6 C charges is 5.6 cm..
Homework Equations
E = kq/r^2
E = F/Q
E = V/d
The Attempt at a Solution
Used tan and sin of 50 to find all...
Hello,
I am doing electrostatics at the moment and have difficulties to solve the following problem. Any hint that helps me to find the answer will be appreciated!
"On every corner of a square are movable point charges with the charge of 'q'. Where does a fifth movable point charge have to...
Homework Statement
An electron orbits a nucleus which carries a charge of +9.6E-19 C. If the electron's orbit radius is 2.0E-10 m, what is its electric potential energy?
Homework Equations
Ep = kQ1Q2/r
V = kQ/r
V = Ep/Q
The Attempt at a Solution
I tried using Ep = kQ1Q2/r
Ep =...
1. The problem statement, all variables and 'given'/'known' data
A proton accelerates from rest from plate X to plate Y. If the potential difference between the 2 plates is 60.0V, what is the speed of the proton when it reaches plate Y?
2. Governing equations
V = E/q
Ekf - 1/2mv^2The Attempt...
1' after a metal rod rubbing with a cloth, is the metal rod remains neutral in charge whereas the cloth will be positive charge?
2' a small pieces of paper and aluminium foil are attracted by charged metal rods when the rods are brought close to them. however, the former stick to the rod...
Particles of charge Q1 = +62 µC, Q2 = +45 µC, and Q3 = -80 µC are placed in a line (Fig. 16-37). The center one is 0.35 m from each of the others. Calculate the net force on each charge due to the other two.
I have found the forces between Q1 - Q2, Q2 - Q3, and Q1 - Q3.
Here is my...
A uniform electric field has a magnitude of 3.0 103 N/C. In a vacuum, a proton begins with a speed of 2.4 104 m/s and moves in the direction of this field. Find the speed of the proton after it has moved a distance of 1.0 mm.
I am confused with the fact that there is a velocity int his...
Hi. I'am having trouble with 2 of my homework problems. Usually I do pretty good in physics but electrostatics unit turned out to be very confusing for me. I think I figured out all the other homework questions but these 2. I drew those out myself but I think they are pretty understandable...
I know an argument that i don´t like. It say´s:
If there were electric field inside a conductor in electrostaic equilibrium, it would exert force on the charges and move them.
But this argument implies that there are infinite charges inside the conductor. This is not very plausible, if...
1)Two small equally charged spheres, each of mass m, are suspended from the same point by silk threads of length l.The distance between the spheres x<<l.Find the rate dq/dt with which the charge leaks off each sphere if their approach velocity varies as v=a/(x)^0.5, a is a constant...
Hi,
I'm a bit stuck with some things in electrostatics.
My first problem:
in my textbook, when they try to derivate the formula for the potential of a point charge: V(b) = - \int E.d\mathbf{l} = -\frac{q}{4 \pi \varepsilon_0} \int_\infty^b \frac{1}{r^3} \mathbf{r}.d \mathbf{l}
they...
A conicalsurface(an empty ice cream cone) carries a uniform surface charge density sigma.The height & radius of the cone are h & R.Find potential difference between apex & centre of the top
we take the potentisl of the Earth to be equal to zero for solving some problems though the potential of Earth is not equal to zero . why is that ? or when can we do that ?
Hi all,
I have this problem in my physics homework, which is not trivial. This is not a graded homework fortunately but I would like to see the solution for it and learn. I have attached my attempt at solving this problem. Not sure if this is the right way to solve it, and so I would like...
We have a charge distribution in which all the charges are in equilibrium due to electrostatic forces . Can we prove that none of these charges will be in stable equilibrium ?
Magnetostatics -> Electrostatics??
I have a questions and I am afraid that I might look very dumb for asking such questions, so forgive me first.
I heard many times how Maxwell's equations along with Lorents Force Law tells all the story of EM dynamics. So I wanted to see if I can show...
the formula
v = kq1/r +kq2/r
if a charge is -2 micro couloumbs for instance is that put into the equatoin and it becomes minused instead or the sign doesn't effect q in the formula
cuase i remmeber in the f = kq1q2
the sign has no effect
Hey everyone,
I'm not sure if this question warrants the "advanced physics" forums, but it would be nice if some of you smart people could give me a hand with this problem.
Two 5g spheres are charged to +100nC and hung from 1m long strings. What is the angle produced due to the repusive...
Hi everyone, I was wondering if anyone could give me any input on this question over an electrostatics lab I recently did. The part I'm not sure about was a section where we sampled the charges of several different wands by placing them into a Faraday ice pail connected to an electrometer. The...
Answers or Steps, or even formulas are welcome, Any answer to any of them!
Okay First qusetion...
A proton is placed in an electrical field that counters the effect of gravity at sea level. Find The Electric Field.Second Question...
A Proton is accelerated from rest in an electric field of...
The problem says
Verify by direct integration that
F= qE = - q^2/(16*pi*epsilon_0*d^2) in the "x unit" direction
is the resultant of the Coloumb force between q and the induced charge described by
sigma_f(y,z) = -qd/(2*pi*(d^2+y^2+z^2)^3/2
-------------
Okay, I am not sure...
In "Classical Electrodynamics - 3rd Ed.," J.D. Jackson has an exercise, 1.10, to derive the mean value theorem of electrostatics. Does anyone know of a derivation which is located on the web?
Pete
hi,
this is a great forum here and i was wondering if anyone could lend a helping hand , it would be great.
im currently studying at univercity for electronics engineering and have been given some physics questions to work onover the holidays. I ahve spend quite some time on this question...
Electrostatics problem
Hello!
The problem I'm trying to get help on is the following:
You have an evenly charged circle with the total charge Q and radius R. There is also a point-charge q located a (thats a symbol, not an article) meters from the center of the circle (the point charge is...
I have a little doubt. why is there an inverse square law in electrostatics?why not some other than the inverse square? is there any relation/connection between the charges and the inverse square?
the below figure make small angles theta1 and theta2 with the vertical.
Figure 21-50
(a) If Q1 = Q, Q2 = 3Q, and m1 = m2 = m, determine the ratio theta1 / theta2.
(b) If Q1 = Q, Q2 = 2Q, and m1 = m, and m2 = 4m, determine the ratio of theta 1 / theta 2.
I don't get the forces that are...
griffiths electrostatics problem
if you have the text on you, I'm looking at question 2.46 (in the third edition).
i am given
V(\mathbf{r}) = A\exp (-\lambda r)/r
i found that
\mathbf{E} (\mathbf{r}) = A\exp (-\lambda r)(\lambda /r + 1/r^2) \hat{r}
the solution for \rho...
Three point charges of +2μC, +3μC and +4μC are at the vertices of an equilateral triangle ABP, respectively, having sides of 10cm. What is the resulting force R acting on the +4μC charge?
the hint in class is to use the law of cosines
this is how i set it up
force acting on 4uc from...