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.

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  1. J

    SI and Gaussian unit conversion in electrodynamics

    Homework Statement I am reading about electrodynamics, and in different formula, there is a SI form and a Gaussian form. Homework Equations What is the relationship in the different unit system for c or B or E and other relative variables? The Attempt at a Solution sometimes...
  2. D

    Best edition of Jackson's Classical Electrodynamics

    Hello. What's the best edition of Jackson's Classical Electrodynamics? Thank you.
  3. N

    Electrodynamics and Relativity.

    Electrodynamics and Relativity. Please Help! Homework Statement Consider the decay of a particle. (a) Find the threshold kinetic energies of the incident particles in each of the following reactions: (i) ∏+ + p →∏++ ∏° + p (ii) p + n →p + n + ∏° + ∏° The incident particle is the...
  4. L

    Scattering - quantum electrodynamics

    hi, so i have just finished reading my first ever book on quantum electro-dynamics (the feynmann lectures). i am in year 13 of school, or High school some might call it. he draws a diagram in the book (a space time diagram) to represent an electron absorbing a photon and then re-emitting...
  5. J

    Maxwell's equations outside electrodynamics?

    So I've been reading Hehl's Foundations of Classical Electrodynamics - which builds up Electrodynamics from a six of axioms - and their proof that the conservation of charge alone is sufficient to derive the inhomogenous Maxwell equations got me thinking - why don't these extremrly basic...
  6. A

    Complex variables in compound expressions of electrodynamics

    When dealing with electrodynamics it is usual to use complex variables for the electromagnetic field while taking into account that the electromagnetic field is real and that at the end one has to take the real part of the complex solution for the field. However, what happens to compound...
  7. X

    Should I buy Introduction to Electrodynamics (3rd Edition) (Paperback)?

    Should I buy this book for a good price now even though I won't be taking a junior year E@M class till two years from now. I'm asking because I could use Griffiths now as a good reference book. But because it's paper back idk if it will last for two more years. This semester I'm taking an E@M...
  8. F

    Introduction to electrodynamics - help with a dipole problem

    Homework Statement Let the dipole \vec{m} = m\hat{k} be at the origin, and call a certain horizontal axis the y axis. a) On the z axis, what is the angle between the z axis and the magnetic field? b) On the y axis, what is the angle between the z axis and the magnetic field? c) On the cone...
  9. C

    Ampere's Law in Classical Electrodynamics

    I do not know but I do not know if Ampers law is valid for short conductors passing through a loop. I did integrate and my integral was different from the expected I*U. The law seems to be valid only when long conductors pass through a loop but not short ones. Can anyone explain what am missing?
  10. T

    Gauge Freedom of Magnetic Potential in Electrodynamics

    Hi, In Electrodynamics, one often state about the gauge freedom of the magnetic potential. And so, we may choose to impose for example the Coulomb gauge, where the divergence of the potential is zero. But, isn't this only true if there exist no changing electrical field, \frac{\partial...
  11. sunrah

    Energy density (electrodynamics/ Dirac delta etc)

    So I have the following velocity vector of a charged particle in an EM field \dot{\vec{r}} = (v_{0x}cos(\alpha t) - v_{0z}sin(\alpha t), \frac{qEt}{m} + v_{0y}, v_{0z}cos(\alpha t) + v_{0x}sin(\alpha t)) and I have to state the energy density, which is defined as follows: \tau =...
  12. H

    How to Solve the 2D Laplace Equation with Fourier Series in a Grounded Square?

    I don't know how to build up Fourier series for this problem. I tried several times but no results. Can anybody help me. Consider the 2-d Laplace equation for the potential V(x,y) in the region inside an empty square whose sides lie on the lines x = 0, x = a , y = 0, and y = a, respectively...
  13. C

    Suggestions for books of Electrodynamics.

    Hi, I am taking my advanced electrodynamics undergraduate course, and I am following Electromagnetic Theory of Reitz-Milford. The thing is that I want to find books for electrodynamics, that don't take me out of Reitz context but that they are similar. I just want to have more references without...
  14. S

    Intro To Electrodynamics, Griffiths #1.9, me TRANSFORMATION LAW QUESTION

    I would just like to start off by saying the problem comes from Intro to electrodynamics, 3rd edition, griffiths. the problem is number 1.9. Question: Find the transformation matrix R that descries a rotation by 120 degrees about an axis from the origin through the point (1,1,1) the...
  15. soothsayer

    Electrodynamics thought experiment

    So I was thinking about E&M today, and specifically, how E&M relates to the ideas of relativity. Specifically, that magnetism is induced by a change in an electric field and vice versa. This got me thinking of some scenarios. In each, you have a particle emitting a constant magnetic field and...
  16. N

    Physical significance of dot and cross products in electrodynamics

    i know that del.v=divergence of vector v and del x v=curl of vector v can anyone justify for the same? how dot product is physically connected to divergence property?
  17. M

    Exploring Classical Electrodynamics for QED: A Time-Saving Guide

    Hi all, I'd like to improve my understanding of classical electrodynamics, but as a UK PhD student my time for self-study is pretty limited- we don't make much time for general physics education at a graduate level. I was wondering if someone could recommend a short path through Jackson's...
  18. W

    Electrodynamics(?): finding position of particles in function of time?

    Im still on high school so I don't know where this question belongs to, I don't know even what is the exact subject of this question, so I would like you more experienced members to help me understand what exactly I am asking and where I can find information about it: "In an empty universe...
  19. T

    Electrodynamics in two space dimensions :-(

    Hi all, I've got this problem (which is attached as q1.jpg). I've tried to solve it, but I'm stuck... my solution is also attached (my_sol1.jpg). PLS help me :-( Thnx TED
  20. D

    Can complex analysis be used in classical electrodynamics?

    The title may be a bit vague, so I'll state what I am curious about. Since complex field is 'extension' to the real field, and in electrodynamics we use things like Stokes theorem, or Gauss theorem, that are being done on real field (differential manifolds and things like that, right?), can...
  21. M

    Electrodynamics- energy required for 2 charges approaching

    Hi guys, I have a quick q about solving questions where there are two charges q1 and q2 approaching each other (in this textbook problem it is from 0.1 m to 0.01m). I understand that you have to keep one of the charges stationary and use the formula: W=q(Vf-Vi) = q1[ (k*q2)/r2 - (k*q2)...
  22. Q

    Square Conducting Ring - Electrodynamics Question

    Homework Statement Ok I'm going through last year's practice exam for electrodynamics and I'm stuck on a particular problem. For problem statement see attachment. q5a part i is fine but I'm confused with the other parts. Homework Equations...
  23. S

    Often a terminology is used in Electrodynamics

    Often a terminology is used in Electrodynamics "in the absence of static and moving charges" of a magnetic medium. what does this corresponds to and how do Maxwell turns out to be in this situation? Please explain the context in detail.
  24. Z

    Exploring Physics Measurement: Stochastic Electrodynamics

    Hi, there. I am not major in physics so maybe I lack some basic knowledge. Imagine one have an ideal sensor, which can convert the emission to some kinds of signal (typically, voltage), then what process can describe the measure data? Is it related to...
  25. P

    Nonlocal electrodynamics of superconductors

    Hello, Conductivity \sigma (\omega, k) in Fourier space is defined by J(\omega, k)= \sigma (\omega, k) A(\omega, k) In most cases the local limit of k\rightarrow 0 is a good approximation particulalry in type I superconductors and HTC superconductors. I am interested in cases...
  26. Q

    What is the effect of time-varying current on Gauss law in electrodynamics?

    if i have a current carrying straight long wire, I = I0sin(wt) why is gauss law ∇.E = 0? i thought only for steady currents , then the charges reside on surface, that's why 0 charge enclosed, and hence gauss law gives 0 right? so now since i have a time varying current, what should...
  27. Q

    Electrodynamics Causing me to loose interest in physics

    I'm in my final year of undergrad and this semester I'm doing electrodynamics. Well I'm finding the subject to be very dry, difficult Maths and trying to study the content is just boring. Next year I want to go into masters, but I need to decide whether I want to do it in Maths or physics. At...
  28. Q

    One Big problem with Jackson's Classical Electrodynamics

    Homework Statement You can find the problem in Jackson's Classical Electrodynamics 3rd edition. Chapter 10.19.I already calculated the transmission coefficients, but mine are fourth of those given by Jackson. I do not know why. My calculation is based on Problem 10.18. I use dipole moments...
  29. C

    How to Calculate Force and Potential in Electrodynamics Exercise?

    Exercise A uniform linear distribution of charge of \lambda coulombs /meter is situated at a distance r from a point chage Q of opposite sign . (a) Calculate the force of attraction (B) show that force is same as if the linear disteibution were replace by a single charge Q’= 2\lambdar...
  30. Y

    Math topics I need to study JD Jackson Classical Electrodynamics.

    I was told by a friend that I need to study Complex Analysis, Introduction to Analysis on top of PDE. My highest level of math is only PDE. I want to know what other math topics I need for self study in JD Jackson. I know people go to school will have instructor teaching the math in the...
  31. M

    Electrodynamics and chemistry empirical formula

    In my chemistry textbook it says that the only way to get the ratio between the elements in a compound is by experimental means ,so I was wondering why isn't the physical knowledge of electrodynamics able to predict the reaction given the properties of the elements?
  32. L

    I just read in Griffiths 'Electrodynamics' (chapter 12.3) how

    I just read in Griffiths 'Electrodynamics' (chapter 12.3) how magnetism is a relativistic phenomenom, why there had to be a thing like magnetism just given electrostatics and relativity. Is the same true for the weak force and the strong force? Is there also magnetism? If so, how is it...
  33. M

    Help with Jackson Electrodynamics Notation

    Homework Statement I am having some difficulty with Jackson's notation. I am coming from an engineering (not physics) background. First of all, on Page 36 at the bottom of the page, Jackson uses the Dirac delta function d(x-x'). When he integrates his answer is the function at x...
  34. P

    Quantum Electrodynamics in Curved Spacetime

    Does anyone know if there exist a formulation of QED in curved spacetime. If yes could you give me some references to papers in which solution to these problem is described?
  35. S

    Electrodynamics of point particle at relativistic velocities

    do you know any text or reference with extensive treatment on electromagnetic field ,potential & electromagnetic energy of point particle moving straight at relativistic velocities?
  36. Simfish

    What makes Jackson's Electrodynamics so difficult?

    Is it the mathematical sophistication? Or the lack of intuition that some grad students might have? What is the best way to prepare for a course on Jackson's Electrodynamics? Many grad students haven't even taken a formal course in partial differential equations (and don't have much beyond...
  37. S

    On the Electrodynamics of Moving Bodies

    It is known that Maxwell’s electrodynamics—as usually understood at the present time—when applied to moving bodies, leads to asymmetries which do not appear to be inherent in the phenomena. Take, for example, the reciprocal electrodynamic action of a magnet and a conductor. The observable...
  38. Demystifier

    Is Gauge-Free Electrodynamics the Solution to Gauge Ambiguities?

    Today (a revised version of) the paper http://lanl.arxiv.org/abs/0903.4340 attracted my attention. Abstract: We propose a reformulation of electrodynamics in terms of a {\it physical} vector potential entirely free of gauge ambiguities. Quantizing the theory leads to a propagator that is...
  39. Y

    Is introduction to Electrodynamics belong here.

    If I have question in EM at level of "Introduction to Electrodynamics" by David Griffiths, should I post here or in the Introduction to Physics?
  40. Z

    Solving Irodov Electrodynamics Homework: Work Required to Transfer Charge q

    Homework Statement A point charge q is located at the centre O of a spherical uncharged conducting layer provided witha small orifice as shown in figure. The inside and outside radii of the layer are equal to a and b resp. What amount of work has to be performed to slowly transfer a charge q...
  41. C

    Electrodynamics : Oscillating Quadrupole

    Homework Statement Find E for a quadrupole, oscillating sinusoidally. The method suggested is to take two Hertzian dipoles, a distance 'a' apart, and find the superposition of the two. They both have an equal dipole moment, and angular velocity, but have a phase difference of pi between them...
  42. D

    How Can I Effectively Study Electrodynamics and Overcome Its Challenges?

    I didn't quite know if this is in the right section since it's kinda broad question. This semester I have classical electrodynamics and soon I'll have first test. So far we're doing electrostatics, and if we didn't solve problems in class I would have no idea where to start :\ Some of...
  43. A

    Pertinent content in Jackson's Classical Electrodynamics

    Hey all, just wondering if there is some consensus on which topics, covered in Jackson's Classical Electrodynamics (3rd ed), are the most relative to advanced studies in physics - e.g., quantum mechanics, the various field theories, relativity, symmetry and so on... I'm not looking to skip...
  44. D

    How to Calculate Electric Potential and Field for a Charged Line Segment?

    Homework Statement Find the potential \phi and electric field \vec{E} for homogenous charged line segment with the length 2a, that lies between a and -a along the z-axis, if the total charge on the segment is q Homework Equations...
  45. P

    Maxwell stress tensor in electrodynamics

    \hat{N}=\{\vec{E},\vec{D}\}+\{\vec{H},\vec{B}\}-\frac{1}{2}(\vec{D}\cdot\vec{E}+\vec{B}\cdot\vec{H})\hat{1} \hat{1} - unit tensor If I look \{\vec{E},\vec{D}\}. I know that \{\vec{E},\vec{D}\}=\{\vec{D},\vec{E}\}^* But when I can say that \{\vec{E},\vec{D}\}=\{\vec{D},\vec{E}\}? and when...
  46. fluidistic

    Electrodynamics related question

    I've "learned" how to make X-Rays with the Bremsstrahlung effect. That is, we accelerate electrons (that we get by a current passing through a resistance) through a difference of potential and we put a material (generally metallic) so that electrons get "decelerated" very quickly and they emit...
  47. A

    Relative Simultaneity and Electrodynamics: Lorentz Maths

    I am interested in how the Lorentz maths were derived from the Maxwell electrodynamic and field equations. But not in a struct mathemetical sense as the math is outside my range but on a simpler conceptual level. For eg. contraction seems to have relevance wrt electron electrostatic fields and...
  48. D

    Taking Electrodynamics this semester

    I am taking Electrodynamics this semester and we are doing the course with the aid of "david griffith's Intro to electrodynamics" there has been a lot of word that the course is extremely difficult... can anyone tell me ways to prepare for it?
  49. Simfish

    Physics Grad Programs that don't require Jackson's Electrodynamics

    How many grad programs in physics don't require Jackson's Electrodynamics? Which ones among them, in particular?
  50. P

    How Does Charge Distribution Affect Electric Field Calculation with Gauss's Law?

    Homework Statement Circular plate radius R is uniformly charged and the charge of plate is Q. Find the electric field in arbitrary point perpendicular to the plate that passes through the center. Case R\rightarrow \infty compared with a score of Gaussian theorem.Homework Equations Gauss...
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