What is Coulomb: Definition and 232 Discussions

The coulomb (symbol: C) is the International System of Units (SI) unit of electric charge. Under the 2019 redefinition of the SI base units, which took effect on 20 May 2019, the coulomb is exactly 1/(1.602176634×10−19) elementary charges. The same number of electrons has the same magnitude but opposite sign of charge, that is, a charge of −1 C.

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  1. Simfish

    Exploring Long-Range Coulomb Interactions in Space

    I'm just curious, as space offers the huge length scales that could substantially lengthen the attractive interaction between positive and negative charges (although charges will still be repelled from other like charges)
  2. D

    Solve Coulomb Vector Force Q1,Q2 & Q3 Homework - Dan

    Homework Statement Hey everyone, i have a homework question I'm completely stuck on. Coulomb Vector Force Q1= 20nC Q2= -96nC Q3= +250 nC A(y axis)= .30 meters B(x axis)= .40 meters Layout: Q1 . .A . . Q2--------Q3 B Calculate: Vector force F21 on Q1 due...
  3. Femme_physics

    Why does one coulomb equal 6.241 × 10^18 electrons?

    Just like the answer to mole is amount of atoms in 12 grams of carbon12. I wonder, is there a reason behind the amount of electrons in a coulomb?
  4. A

    Coulomb ( Electric force and charge )

    Homework Statement 1. [1pt] What is the total charge of the radon nucleus? (The neutral radon atom has 86 electrons.) 1.38 * 10^-17 C 2. [1pt] What is the magnitude of its electric field at a distance of 9.6 x10-10 m from the nucleus? +1.34 * 10^11 V/m 3. [1pt] What is the...
  5. G

    Lorentz transformation in Coulomb gauge

    Hello I have been having trouble understanding equation 14.25 in Bjorken and Drell "Relativistic Quantum Fields" and how exactly it gets to it. Also I would like to explicitly find/derive what the operator gauge function is. Can anyone help please?
  6. U

    Conceptual question using Coulomb

    1. Homework Statement Calculate the magnitude and direction of the Coulomb force on each of the three charges shown in Figure P15.10. http://www.webassign.net/sf5/p15_10.gif thats 3 cm if its to small to see. 6.00 µC charge Correct answer 46.76N Magnitude to Left 1.50...
  7. G

    Origins of the Coulomb - Understanding How the Unit of Charge Came to Be

    I'm having a difficult time understanding how the coulomb came to be around as a unit of charge. The definition that a coulomb is equal to the charge of 6.24151×10^18 electrons and that the charge of one electron is -1.602176487(40)×10^19 seems to me like circular reasoning. The other definition...
  8. W

    Coulomb Force Point Charges on Cube

    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...
  9. S

    What is the correct math notation for the Coulomb Barrier?

    I am trying to find out what is the correct way to write the mathematical demarkation for the Coulomb Barrier. You know, if I wanted to write the symbol for the radius of the coulomb barrier. If anyone could show me it in the correct font that would be great. NO, this isn't for...
  10. M

    Unusual coulomb potential

    I have seen the Fourier transform of the coulomb potential quite often. However, I have come across a sum expression for an electrostatic potential V_{cb}(r-r') = \frac{1}{V}\sum_{q \neq 0} \frac{4\pi}{q^2}e^{iq(r-r')} It is equation (2.6) here...
  11. X

    Divergence of forward Coulomb scattering?

    Hi, I have a question about the divergence of forward Coulomb (Bhabha/Moller) scattering. I guess the classical analog of it is the Rutherford cross-section divergence, but that can be explained by the infinite impact parameter. In the QED version - the Bhabha/Moller scattering, it is...
  12. M

    Jellium Model: Finite Confinement & Coulomb Interactions

    Is the Jellium model only suitable for an electron gas of infinite volume? If I confined a gas to a finite volume using an infinite potential well, is there still a way to cancel out the infinities in the coulomb interactions between electrons?
  13. B

    Expectation value of Coulomb potential depends on relative spin

    Homework Statement Show that the expectation value of the Coulomb potential v(\vec{r_1},\vec{r_2})=\frac{e^2}{|\vec{r_1}-\vec{r_2}|}, between two electrons depends on the relative orientation of spin of the two electrons. Assume each electron is in the product state form...
  14. H

    Coulomb force vs. Pauli principle in atoms

    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...
  15. P

    Relativistic particle in Coulomb potential - any analytic solution?

    Is there a general analytic solution to the classical motion of a relativistic charged particle in a static Coulomb potential? Of course, the non-relativistic limit is simply Kepler's problem. Quantum effects should be ignored, but relativistic effects (such as E field transforming into B field)...
  16. S

    Coulomb correction for beta decay spectrum

    Hello I am re-reading some of my old textbooks and have come across a simplified (non-relativistic) term used to correct the beta decay spectrum for the coulomb effect of the nucleus on the ejected beta particle. The expression is; F(Z,E) = (2*Pi*n) / (1 - exp(-2*Pi*n)) where n =...
  17. R

    2D Fourier transform of Coulomb potenial

    The result is well known, but i need more details about the integral below \int \mathrm{d}^2x \frac{1}{|\mathbf{x}|} e^{- \mathrm{i} \mathbf{q} \cdot \mathbf{x}} = \frac{2 \pi}{q} I've done the Fourier transform of the Coulomb potential in 3D. But failed to get the right answer in 2D...
  18. C

    1-D coulomb repelling of 3 charges

    Homework Statement Three positive point charges (with charge and mass given) A (+3q, 2m),B (+q, m) ,C(+4q, 7m/31) can move in a line under the coulomb repelling of one another. The movement begins when all are at rest. Initial distance are (left to right lie A, B, C) AB = r, BC = 2r. Then...
  19. A

    Coulomb Potential Energy - discrepancy between like and opposite charges

    The Coulomb potential energy between two point charges is defined as: V=[(q_1)(q_2)]/[(k*r)] Suppose that you have two equal, like charges at a distance L, then V_like=q2/(k*L) Similarly, for two equal, opposite charges, V_opp=-q2/(k*L)=-V_like Both situations experience a force of...
  20. E

    Coulomb gauge and scalar potential

    Hi there, I'm studying the interaction of one electron atom with an electromagnetic field. In every textbook the starting point is the hamiltonian of the system containing the scalar potential and the vector potential. But then the scalar potential is ignored and I don't understand why. I've...
  21. S

    What is residual Coulomb interaction and why does it exist?

    Towards the end of my atomic and quantum course my lecturer makes a note of residual Coulomb interaction and does a few graphs to show the concequences of it are (such as some states not being allowed do to symmetry) and that they favour larger values of angular momentum, but doesn't really...
  22. P

    Deflection Angle in a Repulsive Coulomb Field

    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
  23. M

    QCD Coulomb Singularity: Quarkonium w/ 2 Gluons

    Hi all, I am just new to work on NLO in QCD. I need to know how a Coulomb singularity in QCD is defined? What is the form/expression of this singularity term? Can anyone explain with an example of any Feynman diagram? I am interested in the case of a quarkonium with two gluons in final state...
  24. K

    Time reversal and Coulomb interaction

    I have read that charge is supposed to be invariant under time reversal. Now, if I consider two like charges placed some distance from each other, I expect them to repel and go away from each other. In a time-reversed frame, I expect them to approach each other. Since the separation is...
  25. D

    The wavelength of the virtual photons of the Coulomb force

    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.
  26. C

    Breaking Through the Coulomb Barrier: Solving an Equation

    im generating potentials, however the coulomb is proving tricky. stumbling block is finding a way to write A coth(2x) + B cosech(2x)= (A+B)/2 tanh(x)+(A_B)/2 coth(x) i am at the RHS and need to get the tanh to come out which I am told can be done. the a's and b's might not be quite right...
  27. F

    How Do Numerical and Analytical Solutions Compare in Finite Coulomb Problems?

    Hey guys, I'm doing some numerical solutions to wave equations and i started by checking that my method using NDSolve in mathematica worked by comparing it to the analytic solutions DSolve would produce. Now in terms of numerically solving the schrodinger equation i have done the usual trick to...
  28. D

    How is the Coulomb force transmitted?

    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...
  29. F

    Solving Coulomb Potential with Schrodinger Equation - Roger Newton & Mathematica

    Hey guys, Am reading up on solving the Coulomb potential in the Schrodinger equation and have a few questions. Essentially what i want to do is check that by just plodding along using DSolve in Mathematica i can get the same result that people ages ago did by using fancy analytic tricks, ie...
  30. V

    Maxwell's equations VS. Lorentz & Coulomb force equations

    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...
  31. tom.stoer

    Coulomb interaction and non-trivial topology

    I have a question regarding the Coulomb interaction in spaces with non-trivial topology. Suppose we have D large spatial dimensions (D>2). Then the Coulomb potential is VC(r) ~ 1/rD-2. Usually one shows in three dimensions that the Coulomb potential VC(r) is nothing else but the Fourier...
  32. inflector

    Quantum Tunneling, Coulomb Barriers and Fusion

    I'm trying to find the experimental evidence for quantum tunneling during a fusion reaction. Take the simple D + D -> T + P reaction. I know that the energies required to make this happen are much lower in actual experiment than what would be predicted by Coulomb's model of the electrical...
  33. D

    Simple Coulomb Exec. With Pix

    Homework Statement q1=q3=5uC,q2=-2uC q2 and q3 have d distance so q2 with q1 d=0.1m q3 and q1 have √2d Homework Equations |q1||q2| F=k---------- r^2The Attempt at a Solution :S
  34. I

    Coulomb Gauge Fixing: Adding Gradient & Subtracting Partial Time Derivative

    Coulomb gauge fixes gauge by setting div(A)=0. What has it to do with adding a gradient to A and subtract a partial time derivative from V?
  35. J

    What is the domain of validity of inverse square laws of Newton and coulomb?

    ¿what is the domain of validity of inverse square laws of Newton and coulomb? I think (correct me if this is false) that at the small scale these laws have been verified accurately , but ¿what happens with large distances? :uhh: . ¿Have been done an experiment which measured the electrical...
  36. D

    Why do both Coulomb and Gravity follow 1/r^2 laws?

    I am wondering why both Coulomb and Classical Gravity follow 1/r^2 laws. Weak and Nuclear force fall off at much faster distance scales! Does anyone know why it is that both Coulomb and Gravity have 1/r^2 strength, while the other forces have different distance scales?
  37. N

    How to measure quantity of electricity without Coulomb law?

    Or how did Coulomb measure quantity of electricity while doing his experiments that leads him to claim his famous Coulomb's law. F=k\frac{q_1 q_2}{r^2} You can measure F and r for sure. But how about q1 and q2 ?
  38. S

    Coulomb: Understanding the Fundamental Unit of Electric Charge

    Ok not 100% if this is right place but it's not homework so... What the hell is a coulomb I've looked everywhere and everything seems to be different. So is it the charge on electrons? Or is it a packet of electrons? 6 million million million electrons = coulomb?!?? Sorry if this...
  39. T

    Evaluating the Coulomb Integral of Helium

    1. The problem statement, all variables, equations and given/known data ¨ Hi guys. I am working on solving the stationary Schrôdinger equation of the Helium atom by the variational method using a Slater determinant constructed from Slater type 1s orbitals, and in that respect i need to solve...
  40. K

    Coulomb Gauge vs. Lorentz Gauge transformation

    Given a set of a scalar function V and a vector function, how does one recognize that it is a coulomb gauge or lorentz gauge transformation? Actually there is a method that i use but i am not sure if it is always true: what i do is to make an electric field (from that set and using known gauge...
  41. T

    Relativistic Coulomb Scattering

    Hi. Landau and Lifgarbages give an equation describing the angle of deflection of a charged particle of a given initial velocity and impact parameter. It's given on page 102 of their Classical Theory of Fields, available here...
  42. S

    Lorentz Force and Coulomb Force

    Homework Statement In frame S, two identical point charges q move abreast along lines parallel to the x-axis, 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...
  43. D

    Connecting Newton and Coulomb: Is There a Link Between Their Laws?

    Do you know if someone already found a link between Newton : F = G mm'/r^2 and Coulomb : F = K qq'/r^2 laws ?
  44. D

    Electrostatics, coulomb force between 2 charges

    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 -1.6x10-19C and each proton has a charge of 1.6x10-19C, each neutron has no charge. if all the electrons were at the north pole and all the protons at...
  45. E

    Coulomb potential removes the degnerecay of states

    Hi every one this is the first time in this wonderful forum :) and i have a question i hope i find an answer ? how can the additiona of a smalll (c/r square)term to the coulomb potential removes the degnerecay of states with different (small) L. (quantum defect)? :confused: thanks
  46. Kudaros

    Coulomb force on a line charge

    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...
  47. G

    Coulomb forces needed to pull atoms from solid

    I'm trying to work out the amount of charge needed for atoms to leave the surface of a solid. Here's the scenario, if we have a solid, say a metal for example, and we take some charge out of a certain area of the metal so it is just leaving the surface of the metal, we have a space charge...
  48. L

    Negative potential energy and coulomb force

    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...
  49. R

    The laws of Coulomb versus Ampere and the electromagnetic Machian paradox

    The laws of Coulomb versus Ampere and the electromagnetic Machian "paradox" Here's an apparent paradox that has been tunneling about in my little mind lately. Maybe someone out there can help me with it. Imagine if you will, a vast empty region of space devoid of any visible distant...
  50. T

    Coulomb Blockade & Single Electron Transistors Explained

    Hello! Can someone please enlighten me about coulomb blockade & how its relevant to Single Electron Transistors? Thanks :))
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