What is Electromagnetic: Definition and 1000 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. S

    Electromagnetic field profile around a closed loop

    Is there a way to determine the profile of the field around a charged closed loop - particularly on the direction normal to the plane of the loop, both front and back? For generic values of V, I, B, H, etc., and any dimensions of the loop, any particular formulae possible to obtain? Thank you...
  2. schrodingerscat11

    Solving an Electromagnetic Wave Problem

    Homework Statement For an electromagnetic wave with an electric field given by \mathbf{B}=\mathbf{i} E_o cos (kz-\omega t)+ \mathbf{j} E_o sin (\omega t - kz) where Eo is a constant Find (a) its direction of propagation (b) the magnetic field (c) Poynting vector (d) energy density, i.e., the...
  3. Uberhulk

    What type of energy does Superman absorb and how does he store it in his body?

    In a Superman comic Superman drops a bomb into a sun eater and outruns the explosion, which is 50 times the size of Kepler's supernova. He is hit by the electromagnetic shockwaves but manages to fly out of the way of the wall of radiation. What type of energy did he absorb? What do...
  4. G

    Understanding Electromagnetic Duality: From B_i to E_i Using Tensor Notation

    So, I'm trying to show that by duality B_{i}\rightarrow E_{i}, using tensor notation. I've done it in a different way, and it works (starting from \overline{F}_{ij}, the dual of F_ij), but I would like to get it from B_i directly. Where am I going wrong? This is what I did...
  5. K

    What is the difference between far and near electromagnetic field?

    I have read this wikipedia article, but I still don't understand: http://en.wikipedia.org/wiki/Near_and_far_field Why can EM radiation only be transverse waves? Why can't it travel as a longitudinal wave? If I have two charges in a vacuum, with the straight line between them called 'x...
  6. V

    General solution to the wave equation of electromagnetic field

    Suppose that we have the four-vector potential of the electromagnetic field, [texA^i[/tex] The wave equation is given by $$(\frac {1}{c^2} \frac {\partial^2}{\partial t^2}-\nabla^2) A^i=0$$ Now the solution, for a purely spatial potential vector, is given by $$\mathbf{A}(t...
  7. R

    Did James Clerk Maxwell Ever Draw a Picture of an Electromagnetic Wave?

    Did James Clerk Maxwell Ever Draw a Picture of an Electromagnetic Wave in any of his notebooks? Who was the first one to draw one? Would love to find the first picture representing it all! I am looking for the first example of a drawing looking like this showing the perpendicular sinusoidal...
  8. T

    About the photon carrying the electromagnetic forces

    I’ve read that the particle responsible for the transmission of the electromagnetic force is the photon. Another way to say this is that the photon is the carrier of the electromagnetic force. Having that in mind, let’s suppose that we have an electron resting in vacuum, and suddenly an electric...
  9. G

    Electromagnetic radiation and photons

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  10. sergiokapone

    What is free electromagnetic field?

    Maxwell's equations solutions in vacuum - is a free electromagnetics waves. Such solutions can be obtained even without knowing anything about the charges and currents. Does this mean that such waves is the essence , not related charges, e.g. free electromagnetic waves? Moreover, the Maxwell's...
  11. aditya ver.2.0

    Quantum objects and Electromagnetic waves

    If light is a quantum object, then what are electromagnetic waves that Maxwell predicted?
  12. Pezz

    Spherical EM Wave: Origin at t=0, S & S' Agree?

    Consider two frames: S and S', with S' moving to the right along the positive x-axis or S at a relative velocity v. The origins of S and S' coincide at t = 0. A spherical electromagnetic wave leaves the origin of S the moment S and S' coincide, or at t = 0. If we consider the transformation...
  13. D

    Normal modes of electromagnetic field

    Hey guys, I'm trying to understand the properties of normal modes of the electromagnetic field inside an arbitrary cavity, but I'm having some trouble. By definition, for a normal mode we have \mathbf{E}(\mathbf{x},t) = \mathbf{E}_0 (\mathbf{x}) e^{i \omega_1 t} and \mathbf{B}(\mathbf{x},t) =...
  14. S

    EM Wave Equation in Higher Dimensions: Gravitation Text

    Caution: I'm new at this stuff. On page 573 of Gravitation (Misner, Thorne, Wheeler), they write down what I think is the electromagnetic wave equation for a discussion on Optics, "Next insert the vector potential (22.25) into the source-free wave equation (22.19d):" I am wondering if the...
  15. R

    How Does the Electromagnetic Wave Equation Validate Given Solutions?

    Homework Statement Show that the solution \textbf{E}=E(y,z)\textbf{n}\cos(\omega t-k_xx) substituted into the wave equation yields \frac{\partial^2 E(y,z)}{\partial y^2}+\frac{\partial^2 E(y,z)}{\partial z^2}=-k^2E(y,z) where k^2=\frac{\omega^2}{c^2}-k_x^2 Homework Equations See above. The...
  16. R

    The Effective Lagrangian of the Electromagnetic Field

    hi to everyone L=T-V as you know it is the lagrangian equation the effective Lagrangian of the electromagnetic field is given by following relation in gaussian units. L=(1/8pi) (E^2-B^2) how is must calculate this relation? (the energy density of electromagnetic fields is given by u=(1/8pi)...
  17. M

    Electromagnetic wave from Maxwells equations in free space

    My textbooks says in a region where there is no charge or current Maxwell's equations read divergence of E=0 Curl of E=-dB/dt all d are partial Divergence of B=0 Curl of B=ue(dE/dt) I get the math of showing that there are waves, but I don't get some of these conditions. 1st don't you...
  18. A

    Electromagnetic Rail gun and a circular track

    Two parallel electromagnets situated symmetrically on either side of the straight section of an oval track propel a wheeled trolley along the track, so that the trolley is in continuous motion, as long as the current is supplied to the electromagnets. Is this workable? Does the entry and exit...
  19. DivergentSpectrum

    How to limit processing demand simulating electromagnetic trajectory

    so suppose i have a wire given parametrically by C(t)=x(t),y(t),z(t), and i run a current of I amps through it. to find the total B field i would sum up the contributions over the length of the wire, and (please tell me if I am wrong) the total B field due to the wire at point p=xp,yp,zp would...
  20. C

    Electromagnetic waves and the correspondence principle

    Hi! In classical electromagnetic theory the energy of an electromagnetic wave is proportional to its amplitude squared. In contrast, the quantum mechanical equation ##E = \hbar \nu## states that the energy is proportional to the frequency of the wave (photon). Now, according to the...
  21. T

    Instruments with electromagnetic nozzle

    I recently saw an technical instrument that uses electromagnetic field to capture and move small objects. For example it can be used to capture and unscrew nut(female screw). How this instrument can be named right to find its description in the Internet?
  22. Dadface

    Beats in electromagnetic waves.

    Hello all. I have been searching for information on wave beats in light but haven't been very succesful. I have found a lot of information on beats but most of it refers to sound or to waves in general without referring to EM waves. I think that when EM waves are dispersed at normal incidence...
  23. P

    Electromagnetic Linear Coupling

    Hello, I am trying to design a way to move a platform that is inside a container without any direct connection to the platform. I hope to have a linear guide outside of the container with an electromagnet attached. When the electromagnet is energized it will couple with the platform...
  24. T

    Need help for electromagnetic repulsion device

    creating force with sound Hi, I am currently building a device for the company I work for to open molds that have been plasticized together using sound. The idea is to produce a frequency that will either vibrate the lid open or push it open, but I am stumped on what calculations I need to use...
  25. R

    Uncovering the Mysteries of Electromagnetic Wave Equations in Antenna Theory

    Is it possible to solve these partial differential equations directly, relating to Antenna Theory; ∇^2 E - μ_0 ε_0 \frac{∂^2E}{∂t^2} = -μ_0 \frac{∂J}{∂t}. AND ∇^2 B - μ_0 ε_0 \frac{∂^2B}{∂t^2} = -μ_0 ∇ x J. I don't like the idea of having to make up fields that don't exist in order to make...
  26. K

    Electromagnetic boundary conditions for a 'current' interface

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  27. J

    Understanding the Propagation of Photons: E-field and B-field in Motion

    Hi PhysicsForums, I was wondering if this youtube was a correct representation of a photon traveling through space with time. What I am trying to grasp is that, is the photon creating a trail of static Efields and Bfields as it moves through space as shown in the youtube, or does the...
  28. L

    How an electromagnetic amplitude becomes QM probability?

    At the core of the quantum concept by Planck was the black-body radiation, then: electromagnetic waves, whose amplitudes are electric and magnetic fields, but when one follow the developments and one comes to the Schrödinger waves, now their amplitudes are not of that kind but related to...
  29. A

    A question about electromagnetic induction

    Hi guys I just want to know why changing magnetic flux in a coil induces emf? Thanks in advance.
  30. R

    Diodes and electromagnetic emmission Help?

    How would one go about figuring out what to dope a diodes pn junction with in order to create a desired electromagnetic wavelength ?
  31. M

    Electromagnetic induction confusion

    I was just thinking about the "changing magnetic field through a loop induces an EMF" and thought of a conceptual question I'm having trouble with. So, imagine you have an open surface where there's a changing magnetic flux that you know (say its a plane of magnetic field coming toward you...
  32. P

    Five questions about electromagnetic radiation

    This is from Wikipedia: 1. What is really meant by "self-propagating", how it works? 2. How many electric and magnetic fields are in one wave? 3. What is the strength of those electric and magnetic fields? 4. What does -q and +q represent in the above diagram? 5. Why would...
  33. P

    Electromagnetic simulators with motion

    Hi all For a recent project, I am looking to simulate a metallic object moving through a magnetic field (think modeling the motion of a solenoid core inside of a coil of wire). I've tried out simulators such as MaxFEM and meep, but I can't seem to figure out how to simulate the motion of an...
  34. R

    Exploring the Charge-less Boson of the Electromagnetic Force

    Why is it that the boson for the electromagnetic force does not have a charge? I apologize if this question is rudimentary, as all of you guys are WAY out of my league. Thanks!
  35. G

    Electromagnetic Field Theory: A Problem Solving Approach

    I stumbled on it while searching for electrodynamics textbooks for undergrads but this seems more advanced than Griffiths. Has anyone else used this book by Marcus Zahn? Is it a worthwhile read for an electrical engineer about to start sophomore year?
  36. T

    In what year was proposed that light is an electromagnetic wave?

    I’m not asking about the duality particle/wave behavior. I just want to know when did the notion of light being an electromagnetic wave first came up. Was it before or after Maxwell’s calculations of the speed of waves? I am currently reading a book that explain the process by which Maxwell...
  37. A

    Electromagnetic waves and charge

    Dear All, Can anyone explain me if light is an electromagnetic wave then why a charge does not experiences an electric force(or magnetic force) due to electric field component(or magnetic field component)of electromagnetic wave? this is a very challenging question asked by my friend to me...
  38. J

    Second Law of Thermodynamics in Terms of Electromagnetic Principles?

    In Heaviside's Electromagnetic Theory (1895) he says that "The second law of thermodynamics itself needs to be established from electromagnetic principles, assisted by the law of averages..." I attempted to Google whether or not anyone has derived the second law via electricity and magnetism...
  39. Abhijeet

    Construct a System with Zero Power Consumption: An Electromagnetic Idea

    I am talking about electromagnetism.. Can we construct a system with no power consumption.. I ve an idea... 1 we can construct rail route surrounded by dome shaped copper (actually cu strips to avoid eddy current) 2 rail on which permanent magnet is fixed will allowed to move on this...
  40. A

    Electromagnetic wave and the phase between the E and B fields

    https://www.physicsforums.com/showthread.php?p=2881300#post2881300 According to the quoted thread above and according to textbooks and Wikipedia the phase between the E and B fields of an electromagnetic wave propagating in free space is zero. This assertion is based on the Maxwell equations...
  41. C

    Constructing the electromagnetic tensor from a four-potential

    *Edit: I noticed I may have posted this question on the wrong forum... if this is the case, could you please move it for me instead of deleting? thanks! :) Hello, I am having problems on building my electromagnetic tensor from a four-potential. I suspect my calculations are not right. Here are...
  42. T

    Complex wavefunctions and electromagnetic waves

    Hi Everyone I am wondering about something. As everyone here knows, electromagnetic waves obviously possesses an electrical component and a magnetic component. Firstly, can electromagnetic waves be considered to be a sort of complex wavefunction? If yes then do the two components of...
  43. Quarlep

    Can light travels without electromagnetic field ?

    Can light travels without electromagnetic field ? Thanks
  44. Ackbach

    MHB Electromagnetic Induction: Problem 30.85 in Halliday and Resnick and Walker

    $\newcommand{\uvec}[1]{\boldsymbol{\hat{\textbf{#1}}}}$ There is a uniform magnetic field $\mathbf{B}$ directed along the axis, and confined to a cylindrical volume of radius $R$. The magnitude of $\mathbf{B}$ is decreasing at a constant rate of $10$ mT/s. In unit-vector notation, what is the...
  45. C

    Origins of the electromagnetic force

    I saw a very old post where someone asked where an electron gets it's charge. Where does the charge come from? Doesn't it arise from the interaction with photons? My understanding is that electric charge and magnetism can not exist without photons, and the electron itself most likely could not...
  46. D

    Amplitudes of Electromagnetic Waves Question

    So I can't find this anywhere, but I would really like an answer as it's driving me up a wall; Are the amplitudes of all electromagnetic waves the same, and if so how are the speeds of the particles that move along the wave not > c? Thanks in advance.
  47. C

    Exercise of Electromagnetic Induction

    Homework Statement Homework Equations That is my solution: The Attempt at a Solution i solve my problem without ø=30°, I confused what this angle was used to do?
  48. T

    Tecnological Electromagnetic Question

    What is the smallest amount of electricity (volts, amps?) required in order to create a magnet capable of spinning a 50 grams steel object 150,000 - 200,000 rounds per minute (rpm)? Phrased another way: What is the smallest electrical engine capable of doing that at the present? 50 grams might...
  49. F

    Calculating Power Dissipation in a Thin Conducting Disc with Induced Currents

    Homework Statement Thin conducting disc, radius a, thickness b and resistivity p (assumed to be large enough induced currents produce no magnetic field). There is a uniform B field B0sin(wt) parallel to its axis. I first had to find the electric field a distance r from the disc axis in the...
  50. L

    North and South of an electromagnetic solenoid

    Homework Statement Explain the location of the poles of the electromagnet. Homework Equations RHR The Attempt at a Solution Is this correct?or are the poles opposite of what they are meant to be. I believe it is south on the left a confirmation would be great thank you :)
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