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 Waves Frequency

    I was watching the lectures on the MIT OCW course 5.111 where it was said that electromagnetic radiations are periodic variations of the electric field. Does it mean that when we are talking about electromagnetic radiation, frequency indicates how quickly do the electric fields change(their...
  2. S

    Can EM Radiation Create Repulsion on Non-Magnetic Objects?

    Can EM radiations produce repulsive effect on on non magnetic objects? If yes how can such fields be produced?
  3. L

    High level defintion of electromagnetic radiation?

    Can someone give me a high level defintion of electromagnetic radiation with some intuition on what the wave form represents (specifically the peaks and valleys)? I am comfortable with the electric and magnetic fields. I would like an explanation similar to the my intuition on the physical...
  4. R

    Heat Generation by Electromagnetic Waves in Semi-Transparent Mediums

    I am trying to figure out how I would go about finding the steady-state temperature distribution in an absorbing medium using the steady-state heat conduction equation: (1) -\nabla\cdot\left(K\nabla T\right) = q_{gen} where T is the material's temperature, K is the material's thermal...
  5. B

    Is the nature of a magnetic field always conservative or is it case dependent?

    Is Magnetic field conservative or non-conservative in nature, I have searched online regarding this, it seems to be a divided house, MIT professor Walter Lewin demonstrated that it is non-conservative using an experiment, but still many arent convinced with the way experiment was conducted...
  6. W

    Electromagnetic potential well, impossible?

    I was having a discussion with my friend the other day. He had just attended a lecture about Paul traps. He told me that the Paul trap potential has a stationary point in the middle, which is a saddle point, and that the 2 pairs of opposite poles are oscillating between being positive and...
  7. J

    What do Electromagnetic waves actually look like?

    Ive asked this question so many times on various forums and i feel there is a simple answer that i just haven't heard yet. I realize that an EM wave is represented as a sine wave, but from what i understand, that's not the physical motion the fields take. Let's say we take a snapshot at the peak...
  8. H

    Why do electromagnetic waves reflect

    I have seen the retarded potentials and what not, but what has always bothered me is why these field solutions reflect when they meet surfaces. I have looked and looked, but there seem to be no analytical explanations for this, only empirical ones. So my gripe is, since electromagnetic waves...
  9. H

    Surfing with electromagnetic waves

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  10. B

    Question with electromagnetic radiation

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  11. B

    Particle moving in electromagnetic field - converting units

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  12. J

    Canceling one electromagnetic wave with another for a part of the radius

    I was curious about electromagnetic waves and whether or not they can be canceled in the fashion I require. First I will state a few principles that I am considering in the paragraph below and the paragraph after will pose the question in full. A Wireless router produces a signal that...
  13. S

    Question on electromagnetic interactions

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  14. R

    Collisions of varying frequencys of Electromagnetic Radiation.

    When Gamma Rays collide it is possible to form various units of matter (ie proton, electron, etc). Does anything happen when photons collide that are of other frequencies other then a ricochet? If X-Rays collide with other x-rays does anything happen? Also, if anything does happen, what would...
  15. J

    How do we know gravity is not just a large scaled electromagnetic force?

    I mean, you can only start to see the effects of gravity when a large amount of matter is in one place. What if all the electric or magnetic fields in every single atom of that planet or star or black hole, ect... combine into one large field, big enough to create what we know as gravity?
  16. M

    What happens to a permanent magnet inside a electromagnetic toroid?

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  17. J

    What do Electromagnetic waves actually look like in space?

    I know they're represented as sine waves but what would they actually look like in space. they wouldn't actually physically go up and down and side to side like a sine wave would they? I have seen representations of sound waves, which i assume is a longitudinal wave, but not a EM wave.
  18. S

    Electromagnetic induction on iron core question

    Homework Statement An iron core with a solenoid coiled around it is in a circuit with a switch and a dc current supply. In front of it, there is a iron ring tied to the ceiling such that it faces the solenoid without touching the circuit. When the switch is turned on what is observed and...
  19. P

    Elementary problems concerning electromagnetic spectrum

    All electromangtic radiation comes under one continuous spectrum. http://en.wikipedia.org/wiki/File:Electromagnetic-Spectrum.png Different wavelengths of this radiation has different properties which is very evident in real life. However the whole concept remains extremely mysterious to...
  20. A

    How Can Wedges Help Simplify Tensor Notation for the Electromagnetic Field?

    This isn't actually coursework, I'm doing some studying on my own. These are my very preliminary attempts to wrangle with tensor notation, so please be patient with me. I'm trying to get the components of the electromagnetic field tensor from \partial^{\mu}A^{\nu}-\partial^{\nu}A^{\mu} But...
  21. E

    Electromagnetic boundary condition

    in electromagnetics , considering boundary conditions of dielectric and perfect conductor , inside conductor E = 0. So, there should not be any time varying magnetic field. But in many books i have seen that inside conductor normal component of B is 0 because there is no time varying magnetic...
  22. L

    Electromagnetic Cores: Finding the Right Materials for Your Magnet

    I'm trying to build a small electromagnet of a 5v breadboard i had set up, but I've run into some troubles. It doesn't work, and I'm trying to figure out if I just need to pump more current through it or if the core I'm using is made of the wrong materials. Does it have to be straight up iron...
  23. G

    Gamma radiation. Nuclear, electromagnetic or both?

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  24. T

    Ideas for practical application of electromagnetic field theory

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  25. P

    What determines which metals will reflect or absorb electromagnetic waves?

    Why does nickel reflect infrared, but gold does not? I've seen devices that shine infrared at a metal surface and measure the reflectance. They're mainly used for looking at thin film coatings. For example, you could have a metal part made of nickel, and thinly coated in gold. The gold...
  26. E

    Understanding the Relationship Between Electromagnetic Radiation and Photons

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  27. C

    Counting electromagnetic modes in a rectangular cavity and boundary conditions

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  28. O

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  29. C

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  30. J

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  31. G

    How is the electromagnetic tensor derived?

    I understand that the EM tensor is a way of expressing the electromagnetic field in a frame invariant way, but how is it derived? Please use the (-+++) convention as I mostly use that.
  32. T

    Does time slow down in an electromagnetic field?

    According to relativity, time rate differs in regions with different gravitational potentials, i.e. the closer we are to the source of gravitation the slower time passes. Does anyone know what happens to time in electromagnetic fields?
  33. N

    Electromagnetic Field Tensor in Curvilinear Coordinates

    How to express electromagnetic field tensor in curvilinear coordinates, that is given a curvilinear coordinates (t,\alpha,\beta,\gamma) with metric tensor as follows: n_{\mu \nu }= \left[ \begin{array}{cccc}h_0^2& 0 & 0 & 0 \\ 0 & -h_1^2 & 0 & 0 \\ 0 & 0 & -h_2^2 & 0 \\ 0 & 0 & 0 & -h_3^2...
  34. S

    Electromagnetic induction near a generator

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  35. R

    Exploring the Electromagnetic Effects of Helium Plasma on Earth & Jupiter

    Given the above quote reference Helium within our Heliosphere, I have a grouping of questions for the electromagnetic wise. If Earth and Jupiter were both placed within a dense Helium plasma region/field of our Heliosphere at the same time; and considering He plasma's high electrical...
  36. S

    Electromagnetic relay(check my solution please )

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  37. S

    Amplitude of a magnetic field of an electromagnetic wave

    If the intensity of an electromagnetic wave is 80 MW/m^2, what is the amplitude of the magnetic field of this wave? (c = 3.0 x 10^8 m/s, permeability of free space ''miu subzero''= 4π × 10^-7 T ∙ m/A, permittivity of free space ''E subzero'' = 8.85 × 10^-12 C^2/N ∙ m^2) 80MW/m^2= 80,000,000...
  38. C

    Generating Electromagnetic Waves

    Every book I ever read describes a electromagnetic wave as a phenomena generated by charged particles accelerating. This will produce a change in electric field that induces a magnetic field. But, due to Maxwell equations a change in magnetic field will also produce an electric field. So, if a...
  39. B

    Momentum Stored inside an Electromagnetic Field

    Quite a vague question here, and I'm not entirely sure I'll be able to get a satisfying answer out of this one, but here goes. Fields such as the electric or magnetic field are introduced as vector fields that allow you to calculate a force at a certain point in space. In this interpretation...
  40. H

    Which of the following will produce Electromagnetic radiation?

    Homework Statement Which of the following will produce Electromagnetic radiation? Explain Your answers. a) Alternating current in a TV transmitter b) The cord of a vacuum cleaner while it is being used c) The circuit of a battery operated CD player d) A positively charged particle...
  41. P

    Electromagnetic Waves' Magnetic Component

    This is just a conceptual question that I've been personally wondering about. So light has a magnetic field wave perpendicular to an electric field wave. I don't quite understand the magnetic field wave though. I thought that magnetic fields were not supposed to have a beginning or end. They...
  42. soarce

    Gravitational vs. electromagnetic waves

    Let's suppose that on Earth I have two devices which permits me to detect the gravitation produced and electromagnetic waves (photons) emitted by the Sun. Then, the Sun suddenly disappears. Which of the two devices will notice first that the Sun has gone, i.e. which wave propagates faster, the...
  43. C

    Electromagnetic waves waves review

    Homework Statement The figure below shows a plane electromagnetic sinusoidal wave propagating in the x direction. Suppose the wavelength is 56.0 m and the electric field vibrates in the xy plane with an amplitude of 20.0 V/m. (a) Calculate the frequency of the wave. (b) Calculate the magnetic...
  44. E

    Electromagnetic induction question

    Hello I am new to this forum and wanted to ask a question on em induction. I know if a current passes through a wire a magnetic field around the wire is produced and can be amplified by having a coil of wire. If that is then placed in a magnetic field (like between a north and south pole...
  45. C

    Bit of confusion with coils and electromagnetic induction

    Apparently for emf to be induced in a coil, the magnetic field (or part of it) has to act along the normal to the coil face. So does this mean that the coil moves side-ways through the magnetic field? where instead of moving through its length (its longer side), it moves through the coil face...
  46. F

    Interference of electromagnetic waves

    I haven't been able to find any literature that answers this question in a pleasing way. Also, all sources on the internet are contradictory. If electromagnetic waves (out of phase since they are emitted by the gaseous atoms in discharge tube) sent through a diffraction gitter interfered with...
  47. throneoo

    Need help with an electromagnetic induction problem concerning two rods

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  48. J

    How Do Electromagnetic and Regenerative Braking Systems Work?

    Homework Statement Q1: explain how the setup shown in the diagram acts as a break? Q2: Electric and hybrid cars use regenerative breaking. At high speeds, the car can be slowed by reversing the direction of the electric motor so that it acts as a generator. Explain how this system...
  49. D

    Electromagnetic radiation in force field

    Say I were to shine a laser in a particular direction and quickly turn it off. After a certain time, the radiation passes through a region of space. Some force field (e.g. electric or magnetic; assume gravity is negligibly small) is then turned on as the radiation passes, such that no mass or...
  50. J

    Electromagnetic inertia induced by surrounding charges?

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