What is Coulomb force: Definition and 44 Discussions
Coulomb's law, or Coulomb's inversesquare law, is an experimental law of physics that quantifies the amount of force between two stationary, electrically charged particles. The electric force between charged bodies at rest is conventionally called electrostatic force or Coulomb force. The law was first discovered in 1785 by French physicist CharlesAugustin de Coulomb, hence the name. Coulomb's law was essential to the development of the theory of electromagnetism, maybe even its starting point, as it made it possible to discuss the quantity of electric charge in a meaningful way.The law states that the magnitude of the electrostatic force of attraction or repulsion between two point charges is directly proportional to the product of the magnitudes of charges and inversely proportional to the square of the distance between them,

F

=
k
e

q
1
q
2

r
2
{\displaystyle F=k_{\text{e}}{\frac {q_{1}q_{2}}{r^{2}}}}
Here, ke is Coulomb's constant (ke ≈ 8.988×109 N⋅m2⋅C−2), q1 and q2 are the signed magnitudes of the charges, and the scalar r is the distance between the charges.
The force is along the straight line joining the two charges. If the charges have the same sign, the electrostatic force between them is repulsive; if they have different signs, the force between them is attractive.
Being an inversesquare law, the law is analogous to Isaac Newton's inversesquare law of universal gravitation, but gravitational forces are always attractive, while electrostatic forces can be attractive or repulsive. Coulomb's law can be used to derive Gauss's law, and vice versa. In the case of a single stationary point charge, the two laws are equivalent, expressing the same physical law in different ways. The law has been tested extensively, and observations have upheld the law on the scale from 10−16 m to 108 m.
I’ve been trying to get the proper understanding of electric field. Fine I get the definition: any charge changes space around itself and thus generates electric field that acts with force on any object that’s relatively close to the charge.
But first from the first, how can the FIELD act with...
First, if we sign the speed in the highest point of the ball's trajectory to be ##v_2##, we can write
##m\frac {{v_2}^2 }{l}=T_2+mg\frac{1}{4\pi \epsilon}\frac{Q^2}{l^2}##.
Now, depending on the ball's particular mass, the electrostatic force can be bigger of smaller than its gravity force...
My professor and the book I'm reading (Particles and Nuclei: An Introduction to the Physical Concepts by Povh et al.) says that "The emitted nucleons are primarily neutrons since they are not hindered by the Coulomb threshold" which means that a neutron has a separation energy lower than a...
Fg = Fc
Fg = 2.3g*9.8m/s^2*cos(28)=19.90N
19.90 = (8.99*10^9)*(4*10^6)*(6*10^6)/(r^2)
1/(r^2) = 92.23
r = 0.104m
However, it's not one of the option...
The image given with the problem:
I found the original problem too difficult to solve, so I thought I'd make it easier by first considering the stationary proton as fixed in place. However, this too proved to be way more difficult than I expected. Here's the updated diagram I used in my attempt...
The only thing tripping me up here is that the answer needs to be in vector form. If the question was asking for the scalar form, then I would just find the distance between the charges (plot the charges according to their vector coordinates, then use pythagorean theorem to find the distance...
In a bound state like atom nucleus (except H1), protons carry a positive charge so repel each other by the Coulomb force. This type of electromagnetic force, (also referred to as electrostatic repulsion) is an inversesquare force (has infinite range characteristics), so a proton added to a...
Let's say a rocket carrying a positively charged balloon starts to accelerate with a constant proper acceleration at time t.
After a long time another rocket carrying a positively charged balloon is launched. The crew of this rocket drives the rocket to a position right below the...
Homework Statement
Twelve equal particles of charge ##+q## are equally spaced over a circumference (like the hours in a watch) of radius R. At the center of the circumference is a particle with charge ##+Q##.
a) Describe the net force acting over ##+Q##.
b) If the charge located at...
Homework Statement
A cork ball is suspended at an angle from the vertical of a fixed cork ball below. The mass of the suspended ball is 1.5x10^4 kg. The length of the suspension thread is .1m. The fixed ball is located .1m directly below the point of suspension of the suspended ball. Assume...
Can charges collapse under coulomb attraction like chargeless matter does under gravity? In a way it's similar to asking about the lower limit of coulomb force if there is any. Also, does Pauli exclusion principle save the day just as in the case of gravity?
Homework Statement
Consider a configuration consisting one +q charge ( upper right) and three −q charges, arranged in a square.
Side lengths = d.
Calculate the total F force vector acting on charge +q.Homework Equations
Vector form of culomb’s force
F=( kq1q2/r^2) rhat
(rhat for unit...
Homework Statement
Two point charges q and 4q are located at r1 and r2, respectively, on the xy plane. The magnitude Q and location R of a third charge to be places on the plane such that the total force on each of the three charges vanishes, are?
first i plotted the problem on the xy...
Homework Statement
One person that we will call him  A is standing on an infinite charged non conductive panel with velocity V=(Vx0,0).
A is throwing a particle q with V=(Vx0,Vy0).
The other person  B, is start running below the particle at t=t0.
A thinks that B will see the particle above...
Homework Statement
Show that the magnitude of the electric force on each ball is given by
Fe = mgtanθ/ (cosα+ sinαtanθ)
where θ = arcsin(x2/L)
α = arcsin((y2y1)/r)
r = √((x2x1)^2+(y2y1)^2)
This is a question from my coulomb's law lab, where 2 styrofoam balls where charged, one was hung on a...
Hi.
Say a positive charge is at (x,y,z)=(0,0,0) at t<0 then (1,0,0) at t>0.
Electric field at (x,y,z)=(l,0,0) is (a,0,0) at t<l/c then (b,0,0) at t>l/c thus a<b.
With time delay of l/c, what propagates from (x,y,z)=(0,0,0) to (l,0,0) ?
I do not think it is electromagnetic wave because it is...
Homework Statement
I was given a task to model (using Matlab) 3 identical particles in external field and find spectra of lowest system energy states using gradient descend method for each particle in the system.
I did a run of 500 random generated coordinates and found this distribution...
Homework Statement
Hi guys! I have a problem pertaining to the kinetic energy gained by a point charge from interacting with a another point charge. Here's the problem: A point charge of mass m1 and charge q is placed near another point charge with mass m2 and charge Q. Both charges are of...
The wellknown connection between the electric field and Coulomb's law is that
The magnitude of the electic field at distance r from a pointcharge Q is E=Q/r^2The definition of E is that the force exerted the field on a pointcharge q is F=qE.
These two equalities yield the F=qQ/r^2...
Homework Statement
An unstrained horizontal spring has a length of 0.32 m and a spring constant of 220 N/m. Two small charged objects are attached to this spring, one at each end. the charges on the objects have equal magnitudes. Because of these charges, the spring stretches 0.020 m, relative...
I'm new to forums and after I typed all this out and tried to submit, it cleared everything. I really need to get this problem finished tonight.
Homework Statement
You have two charges (q1 = 15uC and q2 = 3uC) separated by a distance (d = 3m). We want to calculate the electric field, E...
I am studying Physics Vol2 by halliday, resnick and krane. I was attempting the coloumb force exercises..If we put one charge negative and other positive in the formula..then the force comes out to be negative but the instructor manual for the book ignores the negative charge, and take it as...
This may be a pretty dumb question.
How is it possible for ions and electrons to coexist in plasma state. Shouldn't be there Coulomb force between them so that they would be bound together and become atoms?
Homework Statement
two charges q1 and q2 are palced at a distance r. A slab of thickness t is placed between the two cahrges having dielectic constant k. Find coulomb force between the charges.
Homework Equations
Well F = q1q2 / 4∏ε°k  this would have been the force if the slab was...
Hello,
A typical problem assigned to students is where there are two charges on the xaxis and find the location of a third charge so that the net force on it is zero or some other force value given. I am wondering what is the idea behind this problem? It can get really complicated when...
The definition of Δ (difference,drop of) Electrostatic Potential Energy (D EPE) says it
'is the work done on a unit charge (e) to bring it from r to r1 (against the force) with constant (without acceleration) velocity and extremely low absolute value of velocity (quasistatic, vanishingly...
Hello, I'm having a little trouble with this:
Coulomb Force Point Charges on Cube
Homework Statement
Identical charges of Q (C) are located at the eight corners of a cube with side L (m). Show that the coulomb force on each charge has magnitude:
3.29Q^2/4\pi\epsilon_0l^2
Homework Equations...
Homework Statement
In the absence of the Pauli principle, the Coulomb force would not be saturated, and the energy of a system containing N atoms would vary as N^(5/3).
Show that a system of 2N atoms would have an energy lower than that of two N  atom systems.
Homework Equations
E...
Homework Statement
Find the deflection angle of a particle moving in a repulsive Coulomb field.
Homework Equations
The Attempt at a Solution
Hi everyone,
I can do this no problem if I just knew the equation for a repulsive Coulomb field! Can anyone please help me with this?
Thanks
Is there a way to calculate the wavelength, frequency or energy (per photon) of the virtual photons that charges exchange to account for the Coulomb force? This is assuming that it's always the same wavelength, of course.
Hi everybody, I'd like to pose a few questions that I've had for ages. I haven't found any answers except "read some Quantum Field Theory" so I'd appreciate an explanation in layman's (or in "science educated but not at all expert") terms.
Suppose we have two small charges, one positive and...
I find Maxwell's equations insufficient and superfluous having the Lorentz & Coulomb's force equations. As far as I see magnetic (Lorentz force) and electric (Coulomb's force) interaction is best defined by these two equations themselves, and although Maxwell's equations can describe quite a few...
Homework Statement
In frame S, two identical point charges q move abreast along lines parallel to the xaxis, a distance r apart and with speed v. Determine the force in S that each exerts on the other:
a) using the lorentz force in conjunction with the field of a moving charged particle...
in a mass of 12g of carbon there are NA= 6.02215x1023 atoms, each atom has 6 electrons, 6 protons and 6 neutrons. each electron has a charge of 1.6x1019C and each proton has a charge of 1.6x1019C, each neutron has no charge. if all the electrons were at the north pole and all the protons at...
Homework Statement
We have a source charge that is a uniform sphere with a radius a (centered at origin) and uniform charge density, \rho. There is a line charge with a length L that begins at Z0 and ends at Z0 + L (lies on the Z axis). This line charge has a uniform charge density of...
The coulomb force is given by k*q1*q2/r^2 so if there are two charges that have negative signs, then the force would be negative. Having said that, a "negative force" would then signal an attractive force since opposites attract.
F=dU/dx, so a negative force would result in a "positive...
about coloumb?
i wonder why two point charge whose magnitude 0 and +q(or smt different from zero charge) exert a coloumb force to one another
.formula says there shoud be no force acting to each other(because of multiplication q1.q2=0) but there is an atraction between them .
if this force...
Questions on reversed "Coulomb" force.
I've seen that with Moeller scattering, the attractive force between
the nucleus and the electron can become repulsive at high relativistic
velocities of the electron. What are the energies required for this to
occur?
Is there an analogous result...
Questions on reversed "Coulomb" force.
I've seen that with Moeller scattering, the attractive force between
the nucleus and the electron can become repulsive at high relativistic
velocities of the electron. What are the energies required for this to
occur?
Is there an analogous result between...
I must comment on the Coulomb force  vectorial & nonvectorial form:
F=k*((Q1*Q2)/r^2 )
F=k*((Q1*Q2)/r^2 )*[r] >>>[r] unit vector
I know that , in case of vectorial form, I can use superposition principle, and use this form when the direction is important for me.
But what's more?
A line charge of length L with lamba=const.(linear charge density) lies along the positive Z axis with its ends located at z=z0 and z0+L. Find the total force on the line charge due to a uniform spherical charge distribution with center at origin and radius a<z0
Sooo here's what I DID
I...
Hi
Here is an interesting problem which I have been trying to solve. For convienience of discussion, I have broken it into parts to show where I get stuck:
Two charges Q_{1} and Q_{2} are kept in space at a distance r from each other in a medium of dielectric constant K. The force between...