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. V

    Field lines and Coulomb Forces

    The field intencity around a little spherical conductor changes with reverse ratio to the square of their distance. Then let us put another little spherical charged conductor in field of first one. The field lines are no more change with the reverse ratio to the square of their distance(they are...
  2. B

    Exploring the Physical Meaning of Gauge Transformations in Electromagnetism

    ive just come across gauge transformations on maxwells equations, and mathematically its all pretty straightforward, however, i then come across choices of gauge, with the simplest being the coulomb gauge which is to set devirgence of A = 0 (A vector potential), youve also got the lorentz gauge...
  3. N

    Explanation of particle physics phenomenon - multiple Coulomb scattering

    Homework Statement Hi 1) I read the following article: http://pdg.lbl.gov/2005/reviews/passagerpp.pdf On page 12 of the .pdf there is a figure, figure 27.8, which shows how a charged particle deviates from it's path when scattered by the Coulomb force that comes from the nuclei of the matter...
  4. C

    Exploring the Mystery of Coulomb Force

    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...
  5. Phrak

    Propagating planar wave of the Coulomb potential

    Homework Statement There is a propagating planar wave of the Coulomb potential, \phi = sin(kx - \omega t) . What other fields result when it is assume the magnetic potential, \textbf{A} is everywhere constant? \phi, Coulomb potential \textbf{B}, magnetic field strength \textbf{E}...
  6. J

    Coulomb potential twice problem

    If I describe a system by a Lagrange's function L=-\frac{1}{2}\int d^3x\;(\partial_{\mu}A_{\nu}(x))(\partial^{\mu} A^{\nu}(x)) - \sum_{k=1}^N \Big(q_k A^0(x_k) - q_k v_k\cdot A(x_k) + m_k\sqrt{1-|v_k|^2}\Big) (I'm just coping this from my notes. I'm sure the not gauge fixing Lagrangian with...
  7. O

    Why does Coulomb's Law include a pi in the denominator?

    Homework Statement I'm sure I'm missing something simple here, but to the point: I calculate the electric field a distance r from a uniform straight infinite line charge using Gauss' Law and get an answer; I do the same calculation using Coulomb's law and get the same answer but a pi...
  8. U

    Can Both Lorentz and Coulomb Gauges Be Satisfied Simultaneously?

    Homework Statement For the potentials: V(\vec{r}, t) = ct \vec{A}(\vec{r}, t) = -\frac{K}{c} x \^x c being velocity of light in a vacuum, determine the constant K assuming the potentials satisfy the Lorentz gauge. b) Do these potentials satisfy the Coulomb gauge as well? c) Show that for a...
  9. G

    Significance of Surface and Coulomb Terms

    I recently had a test question posed to me that asked firstly for an explanation of the terms in the semi empircal mass forumla (which I gave correctly) but then went on to ask: For ^{40}_{20}Ca and ^{208}_{96}Pb estimate the fraction of the binding energy provided by the surface and...
  10. S

    Biot-Savart + Coulomb + Charge Conservation = Maxwell?

    Biot-Savart + Coulomb + Charge Conservation = Maxwell?? Do the Biot-Savart Law, Coulomb's Law, and the Law of Charge Conservation contain the same information as Maxwell's Equations? i.e. \begin{cases} d\vec{B} = \frac{\mu_o}{4\pi} \frac{I d\vec{l} \times \hat r }{r^2} \\ \vec{E}=...
  11. R

    Questions on reversed Coulomb 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...
  12. R

    Questions on reversed Coulomb 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 between...
  13. S

    Coulomb barrier in alpha decay

    Can you gurus help me understand in a qualitative way the nature of the Coulomb barrier as it applies to alpha decay? I can intuitively appreciate the Coulomb barrier as it applies to an incoming charged particle, but resources I have been reading apply the same term to the barrier felt by...
  14. P

    Understanding Coulomb Staircase Properties

    I'm having trouble understanding the properties of the "coulomb staircase" using the average integer charge: <n> as a function of the gate charge. How would we go about getting this graph? http://www-drecam.cea.fr/drecam/spec/Pres/Quantro/Qsite/projects/qip.htm It will be the last graph...
  15. S

    How to calculate electrons in one coulomb?

    Hi friends, How'll we calculate how many electrons in one coulomb?Thanks.
  16. P

    Free particle with Coulomb Perturbation

    Homework Statement This is a question I have about something stated in a textbook without much explanation. From Richard D. Mattuck's "A guide to Feynman Diagrams in the Many-Body Problem" Appendix A.1 pg 337 "for example consider the Coulomb interaction between two electrons in a metal...
  17. B

    Exploring the Coulomb Force: Vectorial & Non-Vectorial Forms

    I must comment on the Coulomb force - vectorial & non-vectorial 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?
  18. K

    Coulomb Friction and Motion

    Homework Statement Consider a glass of mass m starting at x=0 and sliding on a table of LENGTH H. For what initial velocites V(naught) will the glass fall off the table if the only force is Coulomb friction? Homework Equations Fcoulomb = -c(dx/dt) where c >0 and is defined as the...
  19. C

    Coulomb Potential Barrier: Is This Calc Right? What's fm?

    The Coulomb potential barrier of a system of two nuclei X and Y is approximately given by VC = ZX*ZY*e2/RN where ZX and ZY are the charge numbers of the nuclei, e2 = 1.44 MeV*fm, RN = (AX1/3+AY1/3) × r0 is the sum of the nuclear radii. r0 is a constant usually estimated to 1.2 to 1.3 fm and AX...
  20. S

    Coulomb force question

    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...
  21. M

    Anyone prove Fourier representation of the Coulomb potential

    I've seen the Fourier representation of the Coulomb potential is -\frac {Ze} {|\mathbf{x}|} = -Ze 4\pi \int \frac {d^3q} {(2\pi)^3} \frac {1} { |\mathbf{q}|^2} e^{i\mathbf{q}\cdot\mathbf{x}} Will anyone show me how to prove it? (yes, it's the Coulomb potential around an atomic nucleus.)...
  22. J

    Solving Coulomb Triangle: Find Unknown Charge q

    I've been trying to figure this problem out for quite awhile but am really struggling, help would be much appreciated. Thank you In the diagram to the right, the net force on the 1.0 mC charge is zero. What is the sign and magnitude of the unknown charge q? So the diagram is a triangle...
  23. I

    Balancing coulomb and gravitational force

    I am supposed to balance the coulomb repulsive and gravitational force in a way that both forces between the Earth and the moon have the same amount. For that I can just use F_C = F_G 1/(4\pi\epsilon_0) * (Q_1*Q_2)/(r^2) = f (m_1 * m_2)/r^2 and then put Q_1*Q_2 on one side. Now I have...
  24. H

    Historically, what came first: coulomb unit or ampere unit?

    Historically, what came first: coulomb unit or ampere unit?
  25. K

    What Functions Transform Potentials Between Coulomb and Lorentz Gauges?

    Suppose A1 and V1 satisfy the coulomb gauge and A2 and V2 satisfy the lorentz gauge. what function S will transform A1 and V1 to A2 and V2? What function W will transform A2 and V2 to A1 and V1?l
  26. T

    2d Coulomb and Biot-Savart laws

    I'm trying to find some sort of simple derivation of these laws in 2d, using the integral expressions of the Maxwell equations. For 2d Coulomb, I found this: Imagine a rod of infinite length along the z-axis, carrying a charge q which is uniformly divided: rho (the charge/volume) =...
  27. G

    Who is Boltzmann, Coulomb, and Avogadro?

    According to Max Planck : Planck's seven (7) primary universal base unit values 1) Planck intensity : (bar-hG/c^5)^1/2/sr = 7.8672231(80) x 10^-46 cd 2) Planck time : (bar-hG/c^5)^1/2 = 5.3904639(43) x 10^-44 s 3) Planck length : (bar-hG/c^3)^1/2 = 1.6160204(35) x 10^-35 m 4) Planck...
  28. maverick280857

    Calculating the Coulomb Force between 2 charges in space

    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...
  29. D

    What is the electrically charged particle that consists of 1 coulomb?

    When it is said, that 1 coulomb is the amount of electric charge carried by a current of one Ampere for 1 second, and that 1 coulomb is 6.24e18 times the charge of an electron, does it mean that 1 coulomb is 6.24e18 electrons? what is the electrically charged particle that consists of 1 coulomb...
  30. B

    Potential energy given to each coulomb of charge

    This is the info I am given... e = 1.6 ´ 10–19 C NA = 6.0 ´ 1023 particles / mole Molar mass of zinc = 65.4 grams In a chemical cell, the energy released by chemical attack on a metal, say zinc, as in many chemical reactions, is about 300 kJ per mole of metal attacked. What is the...
  31. D

    Why Current is Chosen as Base Unit & 2E-7 N/m Force?

    Current is the rate of change of current passing throught a point each second. 1 ampere is defined as the current in two infinitely long straight wires 1m apart in a vacuum which produces a force of 2E-7 N/m on each wire. My question is why we choose current as base unit rather than charge...
  32. B

    Calculate Coulomb Barrier Height & Distance with 7.68MeV Alpha Particle

    Its something that I should be able to figure out easily but my brain is refusing to work this term. So any help will be appreciated. In a scattering experiment, gold nuclei (Au Z=79 A=197) are bombarded by alpha particles (He Z=2 A=4) If the Kinetic Energy of the apha particles is...
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