What is Electrodynamics: Definition and 416 Discussions

Electromagnetism is a branch of physics involving the study of the electromagnetic force, a type of physical interaction that occurs between electrically charged particles. The electromagnetic force is carried by electromagnetic fields composed of electric fields and magnetic fields, and it is responsible for electromagnetic radiation such as light. It is one of the four fundamental interactions (commonly called forces) in nature, together with the strong interaction, the weak interaction, and gravitation. At high energy, the weak force and electromagnetic force are unified as a single electroweak force.

Electromagnetic phenomena are defined in terms of the electromagnetic force, sometimes called the Lorentz force, which includes both electricity and magnetism as different manifestations of the same phenomenon. The electromagnetic force plays a major role in determining the internal properties of most objects encountered in daily life. The electromagnetic attraction between atomic nuclei and their orbital electrons holds atoms together. Electromagnetic forces are responsible for the chemical bonds between atoms which create molecules, and intermolecular forces. The electromagnetic force governs all chemical processes, which arise from interactions between the electrons of neighboring atoms. Electromagnetism is very widely used in modern technology, and electromagnetic theory is the basis of electric power engineering and electronics including digital technology.
There are numerous mathematical descriptions of the electromagnetic field. Most prominently, Maxwell's equations describe how electric and magnetic fields are generated and altered by each other and by charges and currents.
The theoretical implications of electromagnetism, particularly the establishment of the speed of light based on properties of the "medium" of propagation (permeability and permittivity), led to the development of special relativity by Albert Einstein in 1905.

View More On Wikipedia.org
Recent contents Top users
  1. F

    Electric field Difference between Electrostatics and Electrodynamics

    Hello everyone, I have been pondering on the behavior of the E field in conductors. In electrostatics (where the charges are not moving): a) Electric fields are time- independent but position-dependent b) Electric fields are always zero inside a charged or uncharged conductor. At the...
  2. cemtu

    Griffiths Introduction to Electrodynamics (Stokes Theorem Corollary)

    Although Stokes Theorem says that the line integral of a closed surface equals to zero why do we get a non-zero value out of this question 1.11 (and figure 1.33) in the Griffits Introduction to Eletrodynamics Book?
  3. Sophrosyne

    B The nature of virtual photons in quantum electrodynamics

    In quantum electrodynamics, the energy exchange between two charged particles is called a virtual photon, allowing the exchange of quanta of energy between the two charged particles. But these are not the traditional photons of electromagnetic waves. They apparently just arise from the equations...
  4. N

    Studying Self-Studying Electrodynamics- Am I doing it correctly?

    So I am self-studying electrodynamics using Wangsness' Electromagnetic Fields textbook. Now, I have completed till chapter 21 (Maxwell's Equations). From the electrostatics part, out of the total end chapter problems for each chapter, I was able to solve all excluding 2 or 3. That is, if there...
  5. Riotto

    A Canonical momentum ##\pi^\rho## of the electromagnetic field

    In David Tong's QFT notes (see http://www.damtp.cam.ac.uk/user/tong/qft/qft.pdf , page 131, Eq. 6.38) the expression for canonical momentum ##\pi^0## is given by ##\pi^0=-\partial_\rho A^\rho## while my calculation gives ##\pi^\rho=-\partial_0 A^\rho## so that ##\pi^0=-\partial_0 A^0##. Is it...
  6. K

    Rotating and tilting charged disk induces a voltage inside a ring

    As I`` m learning for an upcoming exam I found an electrodynamics problem I struggle with. In the first task I need to calculate the magnetic dipole moment of a uniformly charged,thin disk with the Radius R and a total charge Q which rotates with a angular speed omega round its symmetry axis...
  7. maajdl

    A Canonical quantization of Electrodynamics: physical intuition ?

    Hello, I am freshly retired and enjoy going back to the fundamentals. I followed the wonderful courses by Alain Aspect on Coursera on Quantum Optics 1 and 2 . The quantization of Electrodynamics is really easy stuff. Just follow the correspondence between Poisson brakets and Commutators ... and...
  8. sdefresco

    Electrodynamics: Conducting sphere of radius R cut in half

    Summary: Electrodynamics: Conducting Sphere cut in half to form a gap, and a charge q is placed on the first half-sphere. Find all four σ. A sphere of radius R is cut in half to form a gap of s << R (ignore edge effects) - the first hemisphere is charged with q, and the second hemisphere is left...
  9. U

    Current induced from a changing magnetic field

    This question is motivated by Problem 7.12 in Griffiths Electrodynamics book. I have not included it in the homework section, because I have already solved it correctly. However, I question whether my solution which agrees with the solution's manual is correct. Relevant Equations: $$\Phi =...
  10. S

    Classical Finished undergraduate electrodynamics: what next?

    I am almost finished with Griffiths intro to electrodynamics and was wondering what would be a good graduate level book on electrodynamics that I could self learn. I've also done His quantum mechanics book as well as Sakurai's quantum mechanics, and have a strong background in math (it's...
  11. Amartansh

    Classical Electromagnetic Scattering

    What are the best resources (books/lectures/articles) to learn Classical Electromagnetic Scattering (forward and inverse modelling)? I am an Electrical Engineer so I would prefer some resource which is from an applied perspective. My specific research topic is related to modeling and analyze 2D...
  12. A

    Relativity Has anyone read "Covariant Electrodynamics: A Concise Guide"?

    There is only one review of this book in amazon so I'm hesitant to order it. It is a good book? what make it different than other books that cover the topic like the one of Landau or Melvin Schwartz's ?
  13. Haorong Wu

    Quantum Introductory textbook for cavity quantum electrodynamics

    Hi. I'm having a hard time learning the physical realization of quantum computers. I got stuck with the section of optical cavity quantum eletrodynamics. There are some concepts I am not familiar with. I think I should read some introductory textbooks which cover cavity quantum electrodynamics...
  14. Flying_Dutchman

    Electrodynamics: divergence of E in empty space

    What is the physical significance of fundamental law del.E=0 in free space ?
  15. guiablo

    Electrodynamics, Curl of P and D

    I know that in statics curl of P=curl of D, since the variation of B in time = 0, and I also know that for linear mediums those curls are 0, but I don't know why, and I don't know if there is any expresion always valid. I would like to know where this curl comes from like I know where the curl...
  16. A

    A Is there any Bohmian approach to quantum electrodynamics?

    I know that in some Bohmian papers (like https://arxiv.org/pdf/quant-ph/0303156.pdf), electron-positron pair creation and annihilation is modeled by different methods like stochastic jumps in the configuration space. My question is, is there any Bohmian approach to reproduce all of the...
  17. Aryamaan Thakur

    Electric potential at the edge of a thin charged circular plate

    My question might sound stupid to you but please clear my confusions. I'm taking an circular arc like element on the plate. That arc has a radius of 'r' (AB) and the radius is inclined at an angle 'θ' with OA (∠OAB). The area between arc of radius r and r+dr is dA. dA = 2θr.dr The charge on...
  18. JD_PM

    Arguing about the magnetic force vector

    I am writing about the nature of force in classical mechanics and what does really imply, in terms of change in motion. I am using as an example a circuit, on which we exert a force. I am trying to justify the following scheme (concretely, ##f_{mag}##): The thing is that I am wondering how...
  19. majormuss

    Electrodynamics: Vector Calculus Question

    Why are the red circled Del operators not combining to become 'Del-squared' to cancel out the second term to give a net result of 0?
  20. A

    What is Current? I know it is a scalar but I found something weird....

    While I was going through "Introduction to Electrodynamics" by David J. Griffith I see the line "Current is a vector quantity". But we know it doesn't obey the vector algebra (addition ). Then how it can be a vector?... Please help me
  21. ubergewehr273

    B Doubt on an EM problem regarding gauss law

    There's this problem 2.18 in the book "Introduction to electrodynamics" by Griffith. The problem says the following, "Two spheres, each of radius R and carrying uniform charge densities ##+\rho## and ##-\rho##, respectively, are placed so that they partially overlap (Image_01). Call the vector...
  22. W

    Retarded time calculations: Electrodynamics

    Homework Statement A positive charge ##q## is fired head-on at a distant positive charge ##Q## that is held stationary. It comes in at speed ##v_0## and comes to an instantaneous halt at distance ##r_f## away from Q. What is the amount of energy radiated due to acceleration in this time...
  23. W

    Electrodynamics: Derivatives involving Retarded-Time

    Hi all, I have ran into some mathematical confusion when studying the aforementioned topic. The expression for retarded time is given as $$t_R = t - R/c$$ ##R = | \vec{r} - \vec{r'} |##, where ##\vec{r}## represents the point of evaluation and ##\vec{r'}## represents the source position. I...
  24. W

    Maxwell's equations and exterior algebra

    Maxwell's equations in differential form notation appeared as a motivating example in a mathematical physics book I'm reading. However, being a mathematical physics book it doesn't delve much into the physical aspects of the problem. It deduces the equations by setting dF equal to zero and d(*F)...
  25. W

    Why Are Volume Current Densities Zero on the Surface of Current-Carrying Objects?

    Hi all, I have been reading Griffiths' book on Electrodynamics and have come across a point (image attached below) where he states that volume current densities are 0 on the surface of the current-carrying objects. He then uses these properties in pretty-important integrals. However, I...
  26. W

    Quantum Mechanics and Electrodynamics/Electrostatics

    Hi all, I have a question relating to the title above. The uncertainty relation tells us that an electron that is localised (in terms of its PDF) is space has a large uncertainty in momentum space. However in classical electrostatics/dynamics we seem to make attempts to do things like...
  27. AwesomeTrains

    Effective refractive index of a stratified medium

    Hello PF, I'm reading a paper for a project. In the paper they derive an equation for the effective refractive index ##n=\sqrt{\epsilon^{e} \mu^{e}}## of two stacked layers ##(n_1^2 = \epsilon_1 \mu_1, a)## and ##(n_2^2 = \epsilon_2 \mu_2, b)## where ##a,b## are the lengths and in my case...
  28. Anne Ross

    I Is Quantum Electrodynamics relevant to every electromagnetic field?

    Is Quantum Electrodynamics relevant to every electromagnetic field?
  29. Another

    I'm wondering about the solution (Electrodynamics)

    Total flux is Φ = NΦs where ## N = nl## and Φs is flux due to single loop.In problem 7.24 He solved the problem by using defined of the total flux. Why problem 7.15 He does not solve the problem with using by using defined of the total flux. such as (my solution) Φ = (nl)Φs = (nl)Bπs2 =...
  30. omega_minus

    I Deriving Maxwell's Equations from Field Tensor (Griffith 4ed)

    Hello, I am reading Griffith's "Introduction to Electrodynamics" 4ed. I'm in the chapter on relativistic electrodynamics where he develops the electromagnetic field tensor (contravariant matrix form) and then shows how to extract Maxwell's equations by permuting the index μ. I am able to...
  31. W

    Lagrangian Field Theory - Maxwell's Equations

    Homework Statement $$ L = -\frac{1}{2} (\partial_{\mu} A_v) (\partial^{\mu} A^v) + \frac{1}{2} (\partial_{\mu} A^v)^2$$ calculate $$\frac{\partial L}{\partial(\partial_{\mu} A_v)}$$ Homework Equations $$ A^{\mu} = \eta^{\mu v} A_v, \ and \ \partial^{\mu} = \eta^{\mu v} \partial_{v}$$ The...
  32. Anne Ross

    A Quantum electrodynamics and the brain

    Susan Pocket claims that part of the electromagnetic field of the brain is consciousness and that conscious qualities such as a red car are spatially patterned electromagnetic fields. She also claims that the quantum spatial scale is irrelevant. Intuitively it seems to me Quantum electrodynamics...
  33. CDL

    Studying Higher Year Physics Studies with a Shaky Foundation

    I have just finished my first semester of third year undergraduate physics, and have a 3-4 week break before my next semester, in which I will be taking a third course in electromagnetism (classical electrodynamics). It is my second course with a full focus on electromagnetism, since in first...
  34. U

    Studying Electrodynamics and Classical Mechanics?

    I am preparing for an exam which requires me to solve problems in electrodynamics and electrostatics problems along with classical mechanics and geometrical optics problems. The concern is that I do not have electrodynamics in my course in school so I have to study it completely on my own. I...
  35. vsv86

    Physics Job resources for academic positions in nano-optics and applied electrodynamics

    Hello I am planning to apply for some academic positions (lecturer, assistant professor level and equivalent) in US, Canada and Australia. My field is nano-optics and applied electrodynamics. Can anyone suggest websites where such positions would be advertised? I have googled of course. I get...
  36. W

    Phase relation between the electric & magnetic fields in a plasma

    Homework Statement So I have got the question below. I am asked to find the phase difference between the electric field and magnetic field of electromagnetic waves traveling in a plasma, using the electrical conductivity expression. Now I have found the frequency of the waves and I know that...
  37. Brilli

    Help with an Irodov problem (Problem 3.3 electrodynamics )

    Homework Statement Two small equally charged spheres, each of mass m, are suspended from the same point by silk threads of length 1. The distance between the spheres x << 1. Find the rate dqldt with which the charge leaks off each sphere if their approach velocity v = a/ √x, where a is a...
  38. U

    Studying What do I need before starting to learn electrodynamics?

    I am a high school sophomore and I want to take part in Physics Olympiads which is exactly why I want to learn electrodynamics. I have ordered 'An Introduction to Electrodynamics' by D.J. Griffiths. I am halfway through MIT OCW mechanics course and I know Calculus equivalent to standard Calculus...
  39. Aleberto69

    Electrodynamics: questions about vector and scalar potentials....

    and Lorentz Gauge. Manipulating Maxwell equations and introducing ##\vec A## vector and ##Φ## scalar potentials the following equations are obtained: ## \nabla^2 \vec A+k^2 \vec A=-μ\vec J+\nabla(\nabla⋅\vec A+jωεμΦ) ~~~~~~~~~~(1)## ## \nabla^2 Φ+k^2 Φ=- \frac ρ ε -jω(\nabla⋅\vec...
  40. ubergewehr273

    Why do charged capacitors prevent current flow?

    It is given that an uncharged capacitor is connected with a battery. Clearly, it gets quickly charged and flow of current stops in the circuit. What is the reason behind a charged capacitor in completely restricting the flow of current ?
  41. ubergewehr273

    Non symmetric case of Ampere's law

    When we use Ampere's law, the most basic case that of an infinite current carrying wire is taken whose magnetic field is evaluated at a distance r from the wire. However there's nothing wrong in using the law for non symmetric scenarios. If this is the case how do you explain the B field at a...
  42. ubergewehr273

    Is Ampere's Law Affected by External Currents?

    When we try to find magnetic field due to a set of current carrying wires in a region we draw an imaginary amperian loop and using ampere's law find the magnitude of the magnetic field. ##\oint \vec B \cdot d\vec l = \mu_{0}i_{enclosed}## The RHS involves only the enclosed current inside the...
  43. Dealingwithphysics

    Electrodynamics, Potentials, spherical uncharged shells

    Homework Statement using Laplace principle find potential inside an uncharged spherical shell of finite width. shell is placed in an electric field E in z-axis direction. Homework Equations in this equation u is potential. equation is called 2-D Laplace’s equation. The Attempt at a Solution...
  44. G

    Difficulty with a Point Charge Particle in Electrodynamics

    Point Particle in Relativity and Electrodynamics: “The Classical Theory of Fields” – by Landau and Lifshitz, in its discussion about classical size of a particle, concludes that:- Thus we come to the conclusion that in classical (non-quantum) ‘relativistic mechanics’, we cannot ascribe finite...
  45. sams

    I Finding Real and Imaginary Parts of the complex wave number

    In Griffiths fourth edition, page 413, section 9.4.1. Electromagnetic Waves in Conductors, the complex wave number is given according to equation (9.124). Calculating the real and imaginary parts of the complex wave number as in equation (9.125) lead to equations (9.126). I have done the...
  46. vanhees71

    The Homopolar Generator: An Analytical Example - Comments

    Greg Bernhardt submitted a new PF Insights post The Homopolar Generator: An Analytical Example Continue reading the Original PF Insights Post.
  47. L

    Electric dipole EM field using Lorentz Transformation

    Homework Statement An electric dipole instantaneously at rest at the origin in the frame K' has potentials \Phi'=\mathbf{p}\cdot\mathbf{r}'/r'^3 and \mathbf{A}'=0 (and thus only an electric field). The frame K' moves with uniform velocity \mathbf{v}=\vec{\beta }c in the frame K. Show that in...
  48. whatisgoingon

    XY plane as the interface between two media

    Homework Statement The xy-plane serves as the interface between two different media. Medium 1 (z < 0) is filled with a material whose µr=6, and medium 2 (z > 0) is filled with a material whose µr=4. If the interface carries a current (1/µ0)ˆy (y- hat) mA/m, and B2 = 5ˆx (x-hat) + 8ˆz (z-hat)...
  49. C

    Oscillation of a point charge perpendicular to field lines

    Homework Statement Two particles A and B each carry a charge Q and are separated by a fixed distance D. A particle c with charge q and mass m is kept at the midpoint of A and B. If C is displaced perpendicular to AB by a distance x where x<<<D, find the time period of the oscillation of the...
  50. sams

    A Difference between conduction & convection current density?

    Hello Everyone, Could anyone please explain the difference between the conduction current density (J=σE) and the convection current density (J=ρvd)? I really appreciate any examples or applications to further elaborate these two theories. Note: vd is the particles' average drift velocity...
Back
Top