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. A

    Special relativity - transformation of electromagnetic fields

    Homework Statement In a reference frame ##S## there is a particle with mass ##m## and charge ##q## which is moving with velocity ##\vec{u}## in an electric field ##\vec{E}## and in a magnetic field ##\vec{B}##. Knowing the relativisitc laws of motion for a particle in an EM field, find the...
  2. LonelyElectron

    Electromagnetic induction questions

    Problem: Look at the following diagram: · Copy the diagram and then label the poles for the induced magnetic field and the direction of the induced current · Explain what would happen to the magnetic field and the current if the direction of motion of the magnet is reversed ·...
  3. M

    How long can electromagnetic waves last?

    Hello, I am reading a book on the history of the universe. The book says that we can still detect the electromagnetic waves generated at the big bang in the form of white noise. I am not sure how it works, because the waves transmitted by AM or FM radio antennas die down after propagating some...
  4. CAT 2

    Problems with electromagnetic fields

    Homework Statement Copy the following diagram and draw field lines for both magnetic fields. Then, use them to determine the direction of the force acting on the conductor. HINT: Check your answer, using the right - hand rule for the motor principle. Their diagram: 2. Relevant equation n/a...
  5. S

    Oscillation related to electromagnetic induction

    Homework Statement A copper ring is suspended by a long, light rod pivoted at X so that it may swing as pendulum, as shown in the diagram below. An electromagnet is mounted so that the ring passes over it as it swings. The ring is set into oscillation with switch K open. What happens to the...
  6. T

    What is light exactly? Electromagnetic wave or photons?

    When why sey that light is electromagnetic wave i understand this. But what i do not understand is where photons come into picture ? can somebody explain me the relationship between those two . My knowledge in this respect is not great so I would ask that the answers be adjusted .
  7. Pushoam

    Angular momentum due to electromagnetic induction

    Homework Statement Homework EquationsThe Attempt at a Solution ## \frac { - d \phi }{dt} = V ## V denotes emf. The current is in ## \hat \phi ## direction. Magnetic force is along ## ~\hat s ## direction. Where ## ~\hat s ## is the radially outward direction in cylindrical...
  8. H

    Eye's response to electromagnetic (light) waves?

    Does the eye's retina, rods and cones detect the E or B or both components of a lightwave? I've not been able to find much Googling. Thanks Hank
  9. binbagsss

    Electromagnetic Lagrangian, EoM, Polarisation States

    Homework Statement Attached: Homework Equations Euler-Lagrange equations to find the EoM The Attempt at a Solution [/B] Solution attached: I follow, up to where the sum over ##\mu## reduces to sum over ##\mu=i## only, why are there no ##\mu=0## terms? I don't understand at all. Many...
  10. E

    Gauss' Law for electromagnetic radiation?

    For the proof I've read that verifies transverse electromagnetic waves are consistent with Gauss' Law, there seems to be the suggestion that the magnetic and electric field at a given small length c(dt), along which the waves travel, propagate infinitely backwards and forwards in their...
  11. L

    A Hamiltonian in an electromagnetic field

    I have a question connected with the problem: https://www.physicsforums.com/threads/continuity-equation-in-an-electromagnetic-field.673312/ Why don’t we assume H=H*? Isn’t hamiltonian in magnetic field a self-adjoint operator? Why? Why do we use (+iħ∇-e/c A)2 instead of (-iħ∇-e/c A)2 two times?
  12. V

    I Gravitational Waves Affecting EM Fields: Evidence & Implications

    Suppose a gravitational wave propagating through space encounters a strong magnetic field (for example the wave might pass through a magnetar with a B field strength of 10^{11} Tesla). Would there be any observable perturbation in the magnetic field itself? In other words would the gravitational...
  13. A

    Gravity's effect on electromagnetic field

    Gravity bends light because all charged particles have mass and all electric field starts and ends on some charge particle. Is that a viable explanation for this phenomenon?
  14. I

    Electromagnetic waves/radiation properties?

    As I understand it, light is an electromagnetic wave consisting of an oscillating electric and magnetic fields perpendicular to each other. Are there experiments that will demonstrate (a) there is an electric field present? Stark effect? (b) a magnetic field, (c) that they are perpendicular to...
  15. J

    Joe McFadden magnetic rotors

    I’ve come to this forum because for some reason in my later part of my life I’ve become fascinated with magnetic forces... a dream has driven me to “ let’s get some magnets spinning “ attitude. I am looking for answers and guidance regarding magnetic motors and generator systems.
  16. P

    Find the magnitude of the electromagnetic force on electron?

    Homework Statement In a certain region of space, there is a uniform electric field, E = 4.28 x 104 V/m directed due east, and a uniform magnetic field B = 0.071 T, also directed due east. What is the magnitude of the electromagnetic force on an electron moving due south with a velocity of 3.09...
  17. J

    I Can Electric Fields Affect the Unruh Temperature of Vacuum Fluctuations?

    The Unruh temperature is given by $$T=\frac{\hbar\ a}{2\pi c k_B}.$$ As I understand it one can think of pairs of electrons and positrons popping out of the vacuum and then annihilating. Imagine that we apply an electric field ##\vec{E}## to a region of space. Each electron and positron would be...
  18. T

    Understanding how electromagnetic pulse works

    I heard about electromagnetic pulse, that it can cause damage to electronic devices if one intentionally shots out such a burst. But I wonder, wouldn't that person him/herself be affected by the pulse? I mean, the pulse would work like a lighting. So that person could even die by his/her own...
  19. S

    B Electromagnetic fields of fundamental particles -- help please

    Hi, we know that the particles have intrinsic properties for them electric field and magnetic moment, but for what I mean particles, I mean quarks, the fundamental blocks of (protons, neutrons and mesons) with everything that nobody explained as electric and The magnetic field of a particle and...
  20. E

    Radio waves interaction with other electromagnetic waves

    when it is asked that why radio waves do not interact with the magnetic field of electric wires or magnets, people say that radio waves are not "matter" and they do not have "charge". i really can not understand this for ex think about 2 magnets. The magnet A has a magnetic field and when we put...
  21. T

    Why does electromagnetic induction occur

    Greeting I know the field of electromagnetism is not yet fully clarified but I wonder if there is an idea,theory Why does electromagnetic induction occur only when the conductor cuts the magnetic field lines.
  22. T

    B Electric+Magnetic Force Between a & b Charges: Inertial Frames

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  23. Philosophaie

    Scalar Potentials and Electromagnetic Current

    For a Dipole and a Torad (or a Solenoid) I need to find the scalar Potential,phi, Charge Density,rho, and then 4-Electromagnetic Current,J(rho*c,j) where A and J are 4-vectors and a and j are 3-vectors. -grad^2(phi) + 1/c^2*d/dt(phi) = rho/epsillon0 where grad(A(phi/c,a)) = -1/c^2*d/dt(phi)...
  24. C

    Quantum mechanics transitions in an electromagnetic field

    Homework Statement This is problem (7.1) from John A. Peacock "Cosmological Physics". Show that the first-order perturbation term for quantum mechanics with an electromagnetic field, ##(e/m) \mathbf{A \cdot p}## is proportional to the electric dipole moment. What is the interpretation of the...
  25. S

    What is the effect of electromagnetic fields on the Earth's

    What is the effect of electromagnetic fields on the Earth's magnetic field? Electric energy in the transmission and use of the process, will produce electromagnetic field, the electromagnetic field will have an impact on the Earth's magnetic field? I think it is possible to cause the...
  26. C

    How Are Electric and Magnetic Fields Produced in Electromagnetic Radiations?

    I have encountered a problem that how electric and magnetic fields at perpendicular to each other are produce in electromagnetic radiations?
  27. J

    Polarity of an Electromagnetic Wave

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  28. V

    Classical electromagnetic theory

    According to classical electromagnetic theory,for acceleration a particle must not only change its direction but it should also increase its speed. But Maxwell said that a particle accelerates then it radiates energy.(this is with reference to Rutherford model). But actually the particle is not...
  29. V

    Why Isn't My EM Stress Tensor Calculation Giving the Expected Result?

    Homework Statement An electric field E exerts (in Gaussian cgs units) a pressure E2/8π orthogonal to itself and a tension of this same magnitude along itself. Similarly, a magnetic field B exerts a pressure B2/8π orthogonal to itself and a tension of this same magnitude along itself. Verify...
  30. C

    I If electromagnetic waves propagate, do photons as well?

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  31. C

    I Relativistic Field Transformations and EM Waves

    If we move towards a source of EM waves, in our reference frame the frequency appears (and it is) higher than what a stationary observer will see due to Doppler effect. The field transformations show that these two observers will se static fields differently so I would also expect that the peak...
  32. A

    Electromagnetic Ring Expansion Test

    If my professor tasked me with finding out where to find the materials for setting up an electromagnetic ring expansion test, where is a good place to start? Generally, what is a good procedure to follow when setting up an experiment? I am not very experienced but I would like to learn. The...
  33. J

    Electromagnetic field disturbance if radiation disappears

    Hi everyone! I've been reading about these topics (Feynman lectures and more on the internet and some books) but I still have a doubt, maybe because I haven't understood the whole of it. This is my doubt: Think of an imaginary situation in which we have an accelerating charge. The...
  34. G

    Is Faraday Cage able to stop all electromagnetic radiations?

    I'm trying to understand if it does exist something (material, construction) that shiled you against alll kind of electromagnetic radiations. Something that shields you from the lowest frequency radio waves up to the highest frequency gamma rays. I've read about faraday cage but it does not...
  35. N

    Is the Electromagnetic Field Curved Like Spacetime Near a Charge?

    As far as I know, we can describe the universe as if every bodies uses to follow a straight path in a curved space-time. What kind of role does the electromagnetic field play in all of this? Can we associate a "space-like" field curved by the charge of the particle with it? Does the...
  36. Jin khajama

    Other Studying electromagnetic theory

    I want to study Electromagnetic theory from Zero.Although i have basic knowledge of electrostatics and magnets but i do not feel confident about EM theory.I am undergraduate with Instrumentation and Control Engineering.I am preparing for National level exam in which question related to Emt...
  37. E

    The Peculiar Behavior of a large electromagnetic coil

    I have these two very large (ferrous core) coils, They are basically identical, each 200mm long and have a diameter of 100mm. The core is medium grade steel One coil is receiving an input of 8V(peak-to-peak) @ 4 MHz from the function generator. The second coil is placed 1m away, and is...
  38. Pushoam

    Faraday's law of electromagnetic induction -- Motional EMF

    There is magnetic field in B = B ##\hat z## in a region from x=0 to x=l. There is a metal rectangular wire loop with length l and width w in x- y plane with coordinates of four corners as (0,0),(0,w),(l,0),(l,w). This loop is moved with velocity v=v##\hat x##. Now according to Faraday's law...
  39. 9

    Total moment density of electromagnetic fields

    Homework Statement These is a problem from my textbook. You have an infinite solenoid with n turns per unit longitude, radius "a" and a stationary current I. In the axis there exits a uniform line charge with lineal density λ. Compute total electromagnetic momentum (lineal and angular)...
  40. CorvetteAB

    Automotive Replacing a centrifugal clutch with an Electromagnetic clutch

    Hello friends, Anyone ever thought of, or tried, or has come across an automobile with an EM clutch, probably electronically controlled? We have a CVT driven 2 wheeler with a centrifugal clutch, but we need to disconnect power at will (electronically), so an EM clutch was suggested. Anyone...
  41. C

    Bar magnet wrapped in electromagnetic coil

    If I wrap a coil around a bar magnet and shoot current through the coil so that the magnetic field of the electromagnet is at the same polarity of the bar magnet will I have amplified the magnetic field of the bar magnet maintaining the same magnetic shape but bigger/stronger?
  42. J

    Estimating Electromagnetic Radiation from a Cellular Phone

    Hello all, I have a problem with a typical style of problem I seem to always struggle with. Just to clear this up, I am studying for my comprehensive exams later this summer. So I am going through past problems to bone up on the last two years of grad school. At which point I came across this...
  43. Pushoam

    Range of frequency of electromagnetic waves

    Theoretically speaking, does the frequency of em wave range from 0 to infinity?
  44. infi

    Does an electromagnetic shield reflect?

    Let say a nanoparticle (graphene) is electromagnetic shield. If we send a pulse of magnetic wave will it get reflected back. If it reflects can that be interpreted. And what happens if there going to be infinite EM shielded nanoparticles. Is that any kind signal which will reflects back from...
  45. F

    Physical degrees of freedom of an Electromagnetic field

    As I understand it, the classical source-free electric, ##\mathbf{E}## and magnetic, ##\mathbf{B}## wave equations are solved by solutions for the electric and magnetic fields of the following form: $$\mathbf{E}=\mathbf{E}_{0}e^{i (\mathbf{k}\cdot\mathbf{x}-\omega t)}$$...
  46. D

    Electromagnetic Induction repulsion

    Homework Statement http://imgur.com/a/7CUcU What happens when you close W? What happens when you open W again at Q? If there is a ring of metal at Q, on the coil. Homework Equations There is no relevant equations in this case. The Attempt at a Solution North will be on top and south on the...
  47. G

    Looking for a way to describe Electromagnetic Field

    As the title suggests, I'm looking for a way to explain/describe the EM field to high school seniors. Mechanical transverse waves are easy. But since EM waves travel in a vacuum and require no medium it's hard to form a picture in the mind of the students. What is actually moving?
  48. S

    Difference between probability waves & electromagnetic waves?

    What I know: A ripple/wave in a field gives rise to a particle. For example, a ripple in electric field creates a photon. Question: Is this the same principle as probability wave which when observed reveals a particle?
  49. Gjmdp

    Function of the Electromagnetic spectrum

    Hello. I was playing with functions one aftenoon until I got this one: f(x) = sin(tan(log(x))). I was just wondering whether that function (at least, until the part that it doesn't get too compressed) has the same shape (to say it somehow) as the Electromagnetic spectrum...
  50. R

    Can prisms separate out radio and gamma rays?

    I have a question about electromagnetic radiation, I drew this to better explain what I am trying to understand hopefully it makes some sense but what I was wondering is this... if you take two prism and let the light of the sun enter the prisms like in the picture I drew will they both have...
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