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

    Rutherford scattering - electromagnetic form factor

    Homework Statement Hi there. This is not really a problem, I am only trying to understand something but I simply can't. So Rutherford scattering says that $$ \frac{d\sigma }{d\Omega}=(\frac{Ze^2m}{8\pi \varepsilon _0 p^2})^2\frac{1}{\sin ^4(\Theta/2)}|F(q)|^2$$ where $$F(q)=\int \rho (\vec...
  2. ThatNickGuy

    Superheroes & Electromagnetic Spectrum?

    For years, I've been tinkering away at an idea for a superhero. Without going into too much detail, I thought it'd be cool if he could tap into, control, and even travel through a number of different types of signals: radio signals, satellite signals, wi-fi, etc. Using brain waves, as well, I...
  3. J

    Electromagnetic induction of a closed circular wire

    Homework Statement (See image) a closed circular wire A lies in the plane of the wire B in the circuit. Deduce the direction. Of the induced current in A when (A) the switch is closed (B) the switch is opened (C) the wire A is raised out of the plane of the paper. Homework EquationsThe...
  4. A

    Electromagnetic boundary conditions for symmetric model

    I stumbled upon this article: http://www.comsol.com/blogs/exploiting-symmetry-simplify-magnetic-field-modeling/ Since the article does not contain any mathematical formulations, I was wondering how the boundary conditions can be expressed in terms of magnetic vector potential. From what I...
  5. A

    Electromagnetic filters (color filters)

    Hello all I am searching for electromagnetic filters(color filters) for visible region of EM spectrum with narrow bandpass. I want to filter the white beam with continuous spectrom (400 to 800 nm) into red,blue,green and ...with FWHM about 1 nm around each line. Is there such EM filters? How...
  6. R

    Deriving the electromagnetic field strength tensor

    Just one last question today if someone can help. I'm trying to derive the electromagnetic field strength tensor and having a little trouble with (i think) the use of identities, please see below: I understand the first part to get -Ei, but it's the second line of the next bit I don't...
  7. Y

    Can I Use an Electromagnet to Repel Aluminum?

    Homework Statement I have made an electromagnet using the primary core of a microwave oven transformer and a 1.5 D cell battery. I would like to use the electromagnet to repel an aluminum bar (1 in. dia., 3 in. in length, and 1/4 in. thick; it is shown in the picture) For some reason, the...
  8. L

    Experimenting with Electric Force on a Van Der Graff Generator

    How to carry out an experiment to find range of electric force on a van der graff generator?Thanks!
  9. D

    Neutrons in electromagnetic fields

    Consider a moving neutron passing by an electromagnet, will a neutron be deflected? This video seem to show that the neutron would have to be charged in order for it to move
  10. A

    Electromagnetic induction of two wires

    I have two wires in parallel at a distance r apart. They are unequal in length. The current carrying primary generates a magnetic field B at distance r. What is the area related to the secondary through which B passes? Is it correct to assume the thickness times the length of the secondary? All...
  11. A

    Refraction of Light: Is There No Refraction?

    I understand that when light goes between air and water, refraction occurs (either towards or away from the normal). If the light going between air and water is already going in the same direction as the normal, is there no refraction (or a refraction angle of 0 degrees)? Thank you.
  12. N

    Does electromagnetic radiation actually carry kinetic energy?

    Hi all, Does electromagnetic radiation actually carry kinetic energy? Looking around the web gives different answers. I have seen explanations like radiation pressure experiments as evidence, but this has been argued being effects from energy absorbed by the recipient. In case it does not...
  13. X

    Find frequency of electromagnetic waves

    Can anyone give a solution or guidance about how to solve this. In vacuum, the components of an EM wave are Ey = 50(V/m)cos[(5.00 m-1)x + ωt], Ex = 0, and Ez = 0. What is ω?
  14. Jackson Lee

    A question about electromagnetic induction

    Hey, guys, I encountered this and confused about it. "In a perfect conductor, an arbitrarily large current can be induced, and the resulting magnetic field exactly cancels the applied field." But I suppose, according to Faraday's law,the magnitude of emf is the rate of change of magnetic flux...
  15. N

    Energy carried by electromagnetic waves question

    1. The power radiated by the sun is 3.9 x 10^26 W. The Earth orbits the sun in a nearly circular orbit of radius 1.5 x 10^11 m. The Earth's axis of rotation is tilted by 27 degrees relative to the plane of orbit, so sunlight does not strike the equator perpendicularly. What power strikes a...
  16. Jon Mel

    Gravitational Effect of Electromagnetic Radiation

    Hello PPer's, I have been considering the effect to which electromagnetic radiation emitted from stars might play in the gravitational coalescence of galaxies. Surrounding every galaxy there must be a halo of electromagnetic radiation streaming outwards at the speed of light which diminishes...
  17. Y

    Is light is a electromagnetic wave ?

    Electromagentic waves travels at the speed of light that is 3.0 × 10^8. Is the light itself is electromagnetic wave because if the light is a transverse wave which is the electromagnetic wave is transverse too does that makes the light as an electromagnetic wave ?
  18. Z

    Elastic Potential Energy to Aid Electromagnetic Induction

    Matter can neither be created nor destroyed...but potential energy can be converted into a different kind of energy. Let's say we have a spring with a mass connected to it. This mass is a magnet, and the apparatus is inside a copper coil. It's a horizontal magnet with friction minimized at the...
  19. Aafia

    What are electromagnetic waves

    I am confusing about it that what are electromagnetic field books said that it does not require medium then how they propagate in vacuum and we also know that waves are disturbance through a medium
  20. A

    Understanding EM Spectrum: Emitting vs. Reflecting | IR Camera Examples

    Hello, I was wondering how one would be able to tell the difference between an object emitting a certain wavelength of the EM spectrum, vs. an object reflecting that same wavelength of the EM spectrum. For example: 1) Suppose I have an IR source at 7 microns. I point this source at water, and...
  21. M

    Understand Electromagnetic Force in Different Inertial Frames

    I've attached an image to a conceptual problem I'm having a little trouble understanding. It shows part a, b, c, and d (but d is cut off). a and b are one inertial frame while c and d are another. c and d makes sense, but I'm having a little trouble with a and b. Based on the image for c, there...
  22. T

    About the photon exchange and the electromagnetic force

    As many of you know better than me, photons are the carriers of the electromagnetic force, so they exchange is necessary for example in order to keep an electron around a proton in a hydrogen atom. So how does this work exactly? What is this “exchange”? In the mentioned system, which one of the...
  23. davidbenari

    E=cB and electromagnetic energy density

    I have to questions that I can't seem to understand. I've seen in my textbook the relation E=cB being deduced from Faradays law applied to some type of rectangular loop. The problem is this is done with regards to a planar wave. So is this relationship general for all EM waves? If so, how? And...
  24. J

    Can electromagnetic waves be turned into each other?

    hey, i was wondering if this can be possible by human force, if so why are we not finding this?
  25. lukestar

    About "Light", need better understanding of it.

    Is there different types of light/particles of light? because all of these lights are different how it works, laser light, light from flash light, sun light. Why does flash light only illuminate only less area/more area depending on how much volts the battery is and a sun illuminates a whole...
  26. B

    Planetary Electromagnetic Field

    First of all I'm not sure where in the world this topic would fit at, so I put it in Electrical Engineering because my assumption is that electrical engineers may have the answers for this question more so than anyone else, but mods, if you feel this thread would be better off in a different...
  27. G

    What does the symbol sigma represent in electromagnetic calorimetry equations?

    Quick question regarding E-Cals. I am giving a presentation on them soon and I understand just about everything I am supposed to, but I keep encountering one symbol and I simply don't understand what it is supposed to mean. ##\frac{d\sigma}{dx}=\frac{A}{X_0N_A}\bigg[1-\frac{4}{3}x(1-x)\bigg] ##...
  28. J

    Electromagnetic Repulsion Power

    So I coiled ~3' of 28awg wire in a 1/4" coil and connected it to an AA battery. It is unable to pick up nuts but still attracts and repulses in the presence of a permanent magnet. When a piece of iron is added to the center of the coil the strength of the magnet increases, as expected, and it is...
  29. P

    Shape of electromagnetic field

    hello what are the shapes that a magnetic (of electromagnetic origin, so that it will be able to vary in intensity and switch on/off controlled by electricity) can have? for example, can we create an electromagnetic in the shape of a cylinder of specific dimensions? ie. to produce an...
  30. D

    Electromagnetic inductance -- Mutual inductance

    I know that- The change in current of primary coil changes the magnetic flux linked with the secondary coil and this an emf will be induced in secondary coil (which also has an inductor in the circuit) so current grows in secondary coil and the current in secondary coil produces magnetic field...
  31. P

    Exploring the Effects of Electromagnetic Materials on Neutron Decay

    hello which is the lightest material that electromagnetism can set it in motion? thanks!
  32. C

    Electromagnetic holding force to size of Magnet Ratio

    Hey all, I'm new here and hoping to enjoy glorious physics with you all! I have a problem and a question; the problem is I don't know much about electromagnets and want to build something rather involved using an electromagnet. XD The question shall be explained.. General Concept: I'm going...
  33. A

    Electromagnetic Radioation Optics

    A convex mirror has a focal length of 16cm. How far behind the mirror does the image of a person 3.0m away appear? I've tried using the equation 1/f = 1/do + 1/di The answer to the solution is -15cm but I'm not sure how to get there. I'm thinking that it might have something that deals with...
  34. Jewish_Vulcan

    Electric Field vs Magnetic Field vs Electromagnetic waves

    How are all of the above fields different from each other what makes them what they are?Any comments would be appreciated.
  35. J

    Propagation of electromagnetic wave

    will the distance traveled by an em wave depends on temperature,if so then explain
  36. P

    Electromagnetic Coil Strength from Moving Liquids?

    I was reading about drift velocity and according to http://amasci.com/miscon/speed.html 100VDC at 1A moving through ~12 AWG wire would produce an electron velocity of 8.4 cm/hr. Since that is incredibly slow I'm curious if a charged fluid (something like the oil used in an oil-based van de...
  37. J

    Electromagnetic emission lines for a hydrogen atom

    Homework Statement Hi, I've been unable to find a relevant thread for a question that I've been stuck on for a couple of days now. Here it is; One of the electromagnetic emission lines for a hydrogen atom has wavelength 389nm. Assiming that this is a line from one of the Lyman (nf =1 )...
  38. B

    Matter Waves and Electromagnetic Waves

    I don't know if this question should be in the quantum physics section, so I'm just posting it here. So I have doubts regarding matter wave and electromagnetic waves associated with electron or just any particle. 1. So I understand when an electron is accelerated, it produces electromagnetic...
  39. T

    Electromagnetic Interference in Cell Phones

    Consider two adjacent people speaking in cell phones. Why the signals don't interfere with one another? Does each phone communicate with a distinct frequency? If so, how?
  40. P

    Basic question in electromagnetic duality

    We originally have $$\overrightarrow{\nabla}\cdot\overrightarrow{B} = 0$$ $$\overrightarrow{\nabla}\times\overrightarrow{E} = -\frac{\partial \overrightarrow B}{\partial t}$$ When electromagnetic duality is concerned this rank 2 tensor kicks in:$$G^{\mu\nu}$$ And most of books and sites...
  41. C

    Electromagnetic Induction and a coil of wire

    The magnetic field that is oriented perpendicularly through a 9.2 cm diameter coil of wire drops from 6.4 T to 6.1 T in 0.076 seconds. What is the emf induced in the coil? Trying to answer this. My question is, if they are perpendicular then does that mean that cos90 makes phi = BAcos theta...
  42. S

    How to hide from the electromagnetic spectrum/electrical pol

    Hello. I need help! is it possible to create a box/cage (ive seen the faraday cage etc) to give one 100% protection from all/some the electromagnetic spectrums - and from electrical pollution? "Nothing enters and nothing leaves" style, so it but cut out all that comes outside of it, and blocks...
  43. A

    Electromagnet with high remanence

    I am in search of an electromagnet which has high magnetic remanence (or retentivity) even when the current through the electromagnet is zero. Can someone provide information about such a material?
  44. TrickyDicky

    Electromagnetic tensor and restricted Lorentz group

    How exactly is the EM field tensor related to the proper orthochronous Lorentz group?
  45. C

    Image formation in terms of electromagnetic waves

    In texts on geometrical optics I have read that an image is formed where light rays converge -- without an explanation of why. Thus I ask, why are images formed where light rays converge? In particular, what is the answer to this question in terms of the wave theory of light (Electrodynamics)...
  46. 1

    Electromagnetic field generated by a recovery station 20kv

    hello engineers, i have a question . what effect would a recovery station that is power at 20 KV and 50 hz from the local power line would have on the immediate area around it? i mean i know it will produce some electromagnetic field around it, and that is not that good for the rezidents living...
  47. T

    Transparency of light and electromagnetic waves

    Hello, For reasons I’ve read here in this forum, some material (let’s say PVC or paper) are not transparent to light. But light is an electromagnetic wave. If I lower the frequency, that material is now transparent, even if I cannot detect it with my eyes but must use special equipments, the...
  48. R

    Sinusoidal electromagnetic wave help

    Homework Statement A sinusoidal electromagnetic wave from a radio station passes perpendicularly through an open window that has area of 0.700m2 . At the window, the electric field of the wave has an rms value 2.30×10−2V/m . How much energy does this wave carry through the window during a...
  49. stevmg

    NMRI electromagnetic principles

    In nMRIs the strong magnetic field plus the radio wave aligns protons. 1). Which protons? Just the proton ions (actually H3O+) from water; or protons in all molecules that contain hydrogen atoms such as water, fats, carbohydrates, proteins? 2). The relaxation phase does what? As the protons...
  50. 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...
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