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. H

    Experiment Exposing Tissue to Pulsed Electromagnetic Field

    Hai guys, My background is from tissue engineering more towards to biology. I am doing exposure of electromagnetic field to a human sample. I have been assigned to use the magnetic device with the information as followed: The PIC16F886 generates 150 microseconds (µs) of pulse frequency of 80...
  2. Dario56

    I How Do Electromagnetic Lenses Magnify the Image?

    In optical microscope both objective and eyepiece are used to magnify the sample image. Magnification is determined by laws of geometrical optics (intersection of optical beams from the same point of the sample) In electron microscope, electromagnetic lenses are used to magnify the sample...
  3. N

    B Electromagnetic force of Electrons

    If you could command all the electrons in an average human body and get them to spin in synchronicity (a clockwise circle in the horizontal plane) how much magnetic force does that produce? Would it create a force against gravity and make you feel lighter? How much lighter?
  4. M

    I Gravitational Field of Electromagnetic Waves: How is it Generated?

    Hi ! It catches my attention that atomic particles such as protons, neutornes, electrons and their respective subparticles such as Quarks are theoretically formed by high-energy electromagnetic fields such as gamma rays and then the gravitational field that would generate the mass of these...
  5. Falgun

    Classical Electromagnetism textbooks

    I have always been interested in learning more about electromagnetism after going through Resnick Halliday Krane 5th edition. Upon reading a few ( read quite a lot) of E&M book threads, I have come to realize that the following texts are often pitched as alternatives to each other: Griffiths...
  6. O

    I Momentum in electromagnetic waves

    Hi all! These days I am brushing up my knowledge on EM Waves. I begin with the introductory level but I don't mind to engage in an advanced treatment of the topic. At the very basic level I had a high school book, the mentions straightway that if the wave carries with it an energy U, it posses...
  7. Einstein44

    Eddy currents in electromagnetic train

    I know that the magnitude of the eddy currents is proportional to the magnetic field, which means it should increase as I add more magnets. However I am unsure if this approach is correct.
  8. C

    I Electromagnetic Field & Space-Time: Relationship Explained

    What is the relationship between the electromagnetic field and space-time? I am basically assuming that space-time is one big gravitational field. Is there a relationship between space-time and the field (I presume) created by the strong force (however negligible it may be at any significant...
  9. Barblorrane

    I Speed of EM & Mech Waves: Maxwell's Law Explained

    Based on Maxwell's Law, the speed of light can be defined by: $$c= \frac{1}{\sqrt{\epsilon_{0}\mu_{0}}}$$ Based on that, can we find a medium where a mechanical wave travels faster than a electromagnetic one? If so, how does that works?
  10. B

    Waveform of Classic Electromagnetic Induction

    Hi guys, Can someone please provide graphical representation (waveform) of emf induced in coil due to a bar magnet spinning perpendicular to axis of coil. Thanks, SB
  11. practicaleducator

    Calculating Electromagnetic Wave Intensity in a 30 sq m Room

    Hi, If I build a machine that its sole purpose is to radiate xx Hz of electromagnetic wave, how do I calculate the intensity of the waves? Let's say I put it in the room of 30 sq meters. Thank you.
  12. R

    How to find electromagnetic force between nucleus and electron?

    Hello, I'm new here and honestly I'm not a physics student. I'm studying engineering and so, understand little of physics. I am trying to find the bond force of graphene's free electron. That means, the electromagnetic force by which the electron is bound to the nucleus. I can only calculate it...
  13. Homestar1

    Electromagnetic radiation (EMR) threshold

    What is the threshold energy (or frequency) required for an electromagnetic field to transition from a near field to become self propagating (EMR), far field? (If I'm using the right definitions to ask the question correctly). Is this constant or are there other details needed to calculate this?
  14. L

    Electromagnetic effects and Magnetic Fields Questions

    1. When two parallel wires carry current in the same direction, they exert equal and opposite attractive forces on each other. 2. ε=lvBsinθ ε=0.02*5*0.1*sin30 ε=0.005 V 3. Well, a conductor moving through a magnetic field has the potential to induce an emf, but this movement must be in such a...
  15. larginal

    Proof of Electromagnetic Identity: Puzzling Last Expression

    I tried to understand proof of this identity from electromagnetics. but I was puzzled at the last expression. why is that line integral of dV = 0 ? In fact, I'm wondering if this expression makes sense.
  16. J

    Electromagnetic inertial reaction force?

    I accelerate charged particle ##A## causing virtual photons to travel to distant charged particle ##B## which feels an electromagnetic force proportional to ##A##'s acceleration (for a classical field description of this effect see https://www.feynmanlectures.caltech.edu/I_28.html Eqn 28.6)...
  17. B

    Do neuron electrical signals generate an electromagnetic field or wave?

    I'm not sure where this belongs, I'm guessing biomedical, but I'm interested from a physics perspective. Do neurons generate an electromagnetic field? In other words, all the neural activity in the brain, does it generate electromagnetic fields? If so, what are the details of these fields? I...
  18. P

    AdS/CFT electromagnetic wavefunction emergence

    If an electomagnetic wave like blue light, for example, exists in 3 dimensions, then how does/can the AdS/CFT conjecture explain it's emergence? Are the electric and the magnetic components of the blue wave both in 2 dimensions in CFT, and if so how would they combine and emerge into AdS to form...
  19. Narayanan KR

    An Interesting Question on Faraday's Law of Electromagnetic Induction

    On examining Maxwell's third equation which is about time varying magnetic fields (Faraday's electromagnetic induction) we find that time varying magnetic fields produce loops of electric fields in space irrespective of whether a coil is present or not, if any coil is present then these loops of...
  20. F

    Lagrangian for the electromagnetic field coupled to a scalar field

    It is the first time that I am faced with a complex field, I would not want to be wrong about how to solve this type of problem. Usually to solve the equations of motion I apply the Euler Lagrange equations. $$\partial_\mu\frac{\partial L}{\partial \phi/_\mu}-\frac{\partial L}{\partial \phi}=0$$...
  21. waazwag

    Induced voltage difference in a magnetic field

    Hi everyone, I'm currently working on the problem listed above. I'm pretty new to electrodynamics, and I'm learning on my own through a book. I was wondering if someone can please help me through this problem. Here are my thoughts:I think I need to use Faraday's Law of Induction for part (a)...
  22. F

    Electromagnetic Wave in the Y-Direction

    A common equation for an electromagnetic wave is Ey = Eocos(kx - wt + phi). According to this equation, wouldn’t the intensity of the electric field extend indefinitely in the y-direction? How does this make sense?
  23. entropy1

    B Is a photon an excitation of the electromagnetic field?

    Allow me to hijack this thread for a second: a photon is an excitation of the electromagnetic field, right? The photon does not exist until measured. So how can we send a photon in a particular direction, so it has a known position and momentum?
  24. F

    Teaching about electromagnetic radiation & struggling

    Summary:: I teach high school (grade 12) and have always struggled with teaching about electromagnetic radiation. I'm looking for resources aimed at laypeople about EMR that may give me some ideas on how to teach it more clearly. I teach high school (grade 12). We have just finished a unit...
  25. Amathproblem22

    MHB Electromagnetic Radiation and Health

    Well, the title pretty much sums up my question. I want to know about electromagnetic radiation and the effects on human health in your opinions and knowledge! I have done research into the topic and also gone down the road of things like wifi(modern technology) effects on health and most...
  26. Mr_Allod

    Electromagnetic Induction of a Disk

    Hello I'm having trouble finding the right way to apply Faraday's law to this question. I've found the flux through the disc: ##\phi = \vec A \cdot \vec B = B_{0} \sin{\omega t} \left( \frac D 2 \right)^2 \pi ## and the EMF: ##\varepsilon = - \frac {d \phi} {dt} = -B_{0} \omega \cos{\omega t}...
  27. greg_rack

    Parameters and the nature of electromagnetic waves

    By rearranging over and over ratio formulas involving frequency, speed and wavelength, I came up with the equation: fP/fQ=10^-8xVP/VQ This led me to take into account only rows A, B, E, and F... but I can't really understand which one of these is the right one.
  28. Glenn Rowe

    Electromagnetic stress tensor from pressure and tension

    I'm puzzling over Exercise 1.14 in Thorne & Blandford's Modern Classical Physics. We are given that an electric field ##\boldsymbol{E}## exerts a pressure ## \epsilon_{0}\boldsymbol{E}^{2}/2## orthogonal to itself and a tension of the same magnitude along itself. (The magnetic field does the...
  29. PainterGuy

    Electromagnetic mass of an electron

    Hi, I was reading the following Wikipedia article and couldn't make sense of few points. I'd appreciate it if you could help me with it. Source: https://en.wikipedia.org/wiki/Electromagnetic_mass#Rest_mass_and_energy Question 1: What is this "electrostatic energy ##E_{em}##"? Is it some kind...
  30. U

    Strange approach to the line-fed slot antenna electromagnetic problem

    There is a beautiful demonstration, available in the text Robert S. Elliot, Antenna theory and Design, Wiley-IEEE Press, page 17 (Stratton-Chu solution), which shows how the electromagnetic field at each point ## \mathbf { r} ## of a volume ## V ##, with boundary ## S_1, ..., S_N ##: can be...
  31. Glenn Rowe

    I Lorentz Transforms of Electromagnetic Fields

    The Lorentz transformations of electric and magnetic fields (as given, for example in Wikipedia) are $$ \begin{align*} \bar{\boldsymbol{E}}_{\parallel} & =\boldsymbol{E}_{\parallel}\\ \bar{\boldsymbol{E}}_{\perp} &...
  32. L

    I Proving Antisymmetry of Electromagnetic Field Tensor with 4-Force

    I've already made a post about this topic here, but I realized that I didn't understand the explanation on that post. in Chapter 7 of Rindler's book on relativity, in section about electromagnetic field tensor, he states that _and introducing a factor 1/c for later convenience, we can ‘guess’...
  33. Jehannum

    B Are electromagnetic wavelength and quantum wavelength the same thing?

    The classical picture of the electromagnetic wave has electric and magnetic field oscillations which give the wavelength of the light. In the quantum picture, is the wavelength of the (de Broglie) wave function of the photon the same thing?
  34. danielhaish

    Is it possible to measure the general amount of electromagnetic field

    We relating to an electromagnetic radiation as waves. and in waves there is maximum point and minimum point but when there is permanent electromagnetic level there is no disorder or weave . so is it possible to measure it in blank space relative to other places
  35. A

    Light as an electromagnetic wave

    light is electromagnetic wave ,so does it also have magnetic and electric field,like all others waves(micro,gama,xray,radio waves etc..)? i never heard that some one talk about light in sense of magnetic and electric field.. if it has ,why than compass don't response to light?
  36. Uchida

    Minimium diameter of an electromagnetic beam in terms of wavelength

    Is there a limit on the minimum diameter that a collimated electromagnetic beam must have (lasers or masers), in terms of its wavelength, or it is possible to create a beam with its diameter smaller than its wavelength? I'm considering a colimated planar wave directly from the source, and not...
  37. J

    Electromagnetic radiation effect on health.

    Some site I've looked at are https://www.sciencedaily.com/releases/2000/10/001016073704.htm and [Link to garbage site removed]
  38. W

    I QED on electromagnetic interactions in atoms

    I think my main question is pretty much summarised in the TL;DR. I have another related question: Is it possible for one to "create" two fermionic particles of the same charge but a different spin (using creation operators ## \hat{a}_{ \downarrow , + }(x,t)\hat{a}_{ \uparrow , + }(x,t) |0...
  39. sophiatev

    I Transformations of Electromagnetic Fields: Griffiths' Claims

    In Griffith's Introduction to Electrodynamics, chapter 12, he discusses how electromagnetic fields transform when we move from one inertial reference frame to another. On page 553, he claims He then considers how the electric field inside a conductor made up of two parallel rectangular plates...
  40. K

    DIY Electromagnetic Induction Experiment

    So I was watching this video containing DIY experiments on electromagnetic induction . At minute 4:45, the dude pretty much creates a transformer without using an iron core. He runs 30-50 kHz AC in a coil (forming the primary circuit) and then brings another coil with its ends attached to a...
  41. dykuma

    Force density from an electromagnetic field

    My guess is that the force per volume is: $$ \vec F_V = \rho \alpha x \hat x + \vec J \times \beta x \hat y$$ but I'm not sure where to go after that. I'm not given a value for either the charge density or the current density, so I can't simplify the relation much. Further, I'm not sure if my...
  42. F

    I Electromagnetic field according to relativity

    Hello, I am still trying to fully grasp the general idea of the EM field, which always travels at the speed of light regardless of the reference frame, and is represented by a tensor with 16 components in relativity theory. My understanding is that, depending on the observer's frame of...
  43. Bernardtai

    Possible to connect two electromagnets perfectly together?

    Mission: create a pair of electromagnets which always connects (angel) perfectly together. Initially, I design with the following 3 ideas, could any design possible to achieve? 1) First idea is to separate 5 iron core, all close to the edge and connect to the battery source. this attempt is...
  44. J

    Electromagnetic induction in motors

    why does an electrical motor produce an induced back emf which is equal to V-It when terminal speed of electrica, fans or electric drills is reached
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