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.

View More On Wikipedia.org
Recent contents Top users
  1. J

    Infinitely charged wire and moving charge

    Homework Statement There's a uniform infinite line charge with the charge density λ. A point particle with charge q moves with a velocity v parellel to infinite line. What is force exerted on point particle? What is magnetic field seen in ths moving frame(particle frame)? Homework Equations...
  2. Y

    Why electromagnetic waves do not stand still?

    I know that the electromagnetic waves are alternating electric and magnetic fields. But I don't get why the fields can't stand still and alternate at the same point. Why they always move ?? I would prefer a logical and verbal answer rather than a mathematical answer. But if mathematics helps...
  3. M

    Crystal leaving patterns of the electromagnetic spectrum?

    I was bored today so I took this diamond shaped crystal made of glas and simply put in infront of the light emitting from the sun. What I noticed was a lot of lines on the wall that were strangely colored, just like the electromagnetic spectrum. One end was blue, then progressively went to red...
  4. P

    Antennas and electromagnetic radiation

    Antennas work with variable current that leads to accelerations and deceleration ofor the electrons, the frequency of the photon or the electromagnetic radiation I want to generate depends on the change in kinetic energy of the electron E= hf= change of kinetic energy of the electron, according...
  5. C

    Some questions about electromagnetic waves.

    - What exactly is the equilibrium of the waves that is shown on graphs? My understanding is that the oscillations are in the strengths of the field, and different sides of the equilibrium represent different directions of the fields. However, I feel as though this contradicts itself in some...
  6. C

    Electromagnetic Field Sensor

    Which is better and how to do it? Make a spaceship an electromganetic field and go through a sensor so at the end of the race it must pass between the sensors to win, and what sensor would you need for very close width. Saying the spaceship is 20ft wide and both sides must be between the 80ft...
  7. D

    Doubts regarding Electromagnetic fields

    I read in a book that Electromagnetic fields propagate at speed of light and carry energy and momentum. Let's take electric field for example. Electric field is none other than a force per unit coulomb.So 1.How could a force(here field) move as force has no property of moving as force causes...
  8. J

    What is this electromagnetic device called?

    What is this electromagnetic device called? I've seen a couple. There is this one: as well as one similar but you must keep the magnet in motion to generate electricity. I would like to make one of these, but I don't know the name of it which makes it hard to search for instructions and a...
  9. CopyOfA

    Modeling and Measuring an Electromagnetic Coil in ANSYS HFSS

    I've been attempting to model a simple electromagnetic coil using HFSS, and have so far been unsuccessful. I have no problems constructing the coil; this is a simple geometry problem. I have a wire of a known geometry with insulation surrounding the wire, then a construct a helical path and then...
  10. P

    What is the equation for electromagnetic wave frequency?

    Hi there When a charge is accelerated it produces electromagnetic radiation. I was wondering if anyone knew the equation relating the frequency of emitted radiation to the size of the charge and the value of the acceleration. My understanding is that it relates to Maxwell's equations, but I was...
  11. Icy98

    Understanding EMF and Charge Separation in a Changing Magnetic Field

    Homework Statement When there is a changing magnetic flux, emf is induced in the solenoid. The solenoid is made up of circular loops of wire. My first question is, since emd is induced in the solenoid, is there a site of higher voltage and another site of lower voltage? My second question is...
  12. K

    Why do we need electromagnetic waves?

    (Sorry for my poor english.) I'm just wondering why is it necessary to have oscillating EM fields for life existing on Earth. The sun has a magnetic field (I think a static one), so why it's not enough to life exists? Also, why we and other animals only see the objects if the fields are oscillating?
  13. brad2292

    How do we formulate the electromagnetic Lagrangian?

    I'm trying to understand how we set up the lagrangian for a charged particle in an electromagnetic field. I know that the lagrangian is given by $$L = \frac{m}{2}\mathbf{\dot{r}}\cdot \mathbf{\dot{r}} -q\phi +q\mathbf{\dot{r}}\cdot \mathbf{A} $$ I can use this to derive the Lorentz force law...
  14. H

    Electromagnetic induction question, coils and magnets

    Say you have a coil connected in a closed circuit. You then move a magnet inside of the coil and it remains stationary inside of the coil. Is the magnet, even though it is stationary, still inducing an emf in the coil or is it not? I'm guessing it doesn't induce an emf in the coil because...
  15. M

    A Conservation of Electromagnetic Energy-Momentum Tensor

    I'm trying to show that \partial_\mu T^{\mu \nu}=0 for T^{\mu \nu}=F^{\mu \lambda}F^\nu_{\; \lambda} - \frac{1}{4} \eta^{\mu \nu} F^{\lambda \sigma}F_{\lambda \sigma}, with the help of the electromagnetic equations of motion (no currents): \partial_\mu F^{\mu \nu}=0, \partial_\mu F_{\nu...
  16. Neha98

    When Does the Rate of Change of Magnetic Flux Equal Zero?

    When does the rate of change of magnetic flux in linkage with a coil rotating in a uniform magnetic field equal zero?
  17. facenian

    Electromagnetic Force problem

    Homework Statement A circular disk rotates about its axis with angular velocity ##\omega##. The disk is made of metal with conductivity g, and its thickness is t. The rotating disk is placed between the pole' faces of a magnet which produces a uniform magnetic field B over a small square area...
  18. K

    Electromagnetic Waves: P1 & P2 Intensity, T2-T1/C Distance, & B Magnitude

    (I'm sorry for my poor English.) I draw a sketch showing the intensity of the magnetic field at two points p1 and p2, where the distance from the source (a wire carrying a current, for example) to p2 is greater than it's for p1. Is the shape of the curve correct? Is it correct that t2-t1/c is...
  19. Omega0

    Why Does a Second Solenoid Feel a Strong Induction in Electromagnetic Induction?

    Hi, I have a trivial question about electrodynamics. If you have a very long coil, a long solenoid. Keep the current constant and you will have no \vec{B} outside (magnetostatics). Let's write down the Maxwell equations: \begin{matrix} \nabla\cdot\vec{B} &= &0 \\ \nabla\times\vec{E} &=...
  20. tzukishiro

    I Why is the weak force 10^-7 times the electromagnetic force?

    In the case of two protons in the nucleus. I've seen charts with that info, but I don't know how... How can I calculate that ratio? I've looked everywhere, and I can't find anything... Thanks
  21. Karan Punjabi

    Why Doesn't Current Flow Continuously When Magnetic Flux is Permanently Changed?

    Guys, I have read Lenz's law and Faraday's law. My question is when the current is overall trying to keep the magnetic flux constant as that in initial time then if I permanently change the flux then why the current is not flowing through the conductor continuously to keep initial flux constant...
  22. Biker

    How does a magnetic field induce an electric current?

    Trying to understand how a magnetic field induces an electric current Suppose you have a wire in the magnetic field like this: If you move the wire with a velocity of V to the left. Then the magnetic field should exert a force on the wire which ultimately on the charges in the wire. According...
  23. M

    Magnetic Induction: Homework Help

    Homework Statement Homework Equations I am not really good at this topic, but I think you would need both the right hand rules (one that involves finding direction of current via magnetic field as well as the one for finding magnetic force) The Attempt at a Solution So I drew out magnetic...
  24. scitchr

    Electostatic vs Electromagnetic

    Greetings. I am a new member posting for the first time. I teach chemistry and I have spent considerable time attempting to get a definitive answer to this question but have found only contradicting information. My query is regarding the nature of the electric force within and between atoms and...
  25. E

    Electromagnetic repulsion force

    Homework Statement An infinitesimally small bar magnet of dipole moment ##\vec{M}## is pointing and moving with the speed v in the x direction. A small closed circular conducting loop of radius a and negligible self inductance lies in the y-z plane with its centre at x = 0, and its axis...
  26. S

    Energy-Momentum Tensor for the electromagnetic field

    Homework Statement Maxwell's Lagrangian for the electromagnetic field is ##\mathcal{L}=-\frac{1}{4}F_{\mu\nu}F^{\mu\nu}## where ##F_{\mu\nu}=\partial_{\mu}A_{\nu}-\partial_{\nu}A_{\mu}## and ##A_{\mu}## is the ##4##-vector potential. Show that ##\mathcal{L}## is invariant under gauge...
  27. Konte

    I Quantization of electromagnetic field

    Hello everybody, It is known that electric field operator is shown as \hat{E}(r,t)=-i\sum_{k,\lambda}\sqrt{\frac{\hbar\omega_k}{2\epsilon V}}\left(a(t)^\dagger_{k,\lambda} e^{-ik.r} - a(t)_{k,\lambda} e^{ik.r} \right) \hat{e}_{k,\lambda} But if I need to represent an electrostatic field in a...
  28. K

    Electric field and electromagnetic waves

    (sorry for my poor english) I've read that a electromagnetic wave only exists in a particular point of space if in such a point there is a nonlinear change of the electric field in respect to time. Then I took a graph calculator and I derived Coulombs equation for the electric field. The results...
  29. V

    A Problem In Electromagnetic Phenomena

    Homework Statement [/B] In a thin rectangular metallic strip a constant current I flows along the positive x-direction, as shown in the figure. The length, width and thickness of the strip are l,w and d, respectively. A uniform magnetic field B is applied on the strip along the positive...
  30. W

    Help using electromagnetic induction

    Homework Statement I am attempting to create a generator using electromagnetic induction. I am using a push pull system to move a bar magnet through a coil to create current. But I am unsure of the dimensions to build it with and when I attempt to use the equation I get stuck. I am looking for...
  31. TheSodesa

    Electromagnetic wave in glass

    Homework Statement A harmonic EM-wave is propagating in glass in the +x-direction. The refractive index of the glass ##n = 1.4##. The wave number of the wave ##k = 30 \ rad/m##. The magnetic portion of the wave is parallel to the y-axis and its amplitude ##H_0 = 0.10A/m##. At ##t=0## and ##x =...
  32. alexandria

    Effects of Reversing Magnet Motion on Induced Current and Magnetic Field

    Homework Statement Homework Equations no equations required 3. The Attempt at a Solution so here are my answers, can some please verify if these are correct. Thanks in advance :) a) i have no idea if I am labelling the poles correctly, or if the induced current is in the right direction ...
  33. E

    Understanding Electromagnetic Induction and Toppling of a Conducting Ring

    Homework Statement A uniform conducting ring of mass π kg and radius 1 m is kept on a smooth horizontal table. A uniform but time varying magnetic field ##\vec{B} = (\hat{i} + t^2\hat{j} ) T## is present in the region (where t is in sec and the positive y-axis is in vertically upward direction...
  34. F

    Electromagnetic induction in a U shaped conductor

    Homework Statement [/B] A 0.393 m long metal bar is pulled to the left by an applied force F. The bar rides on a parallel metal rails connected through a 42.9 ohm resistor as shown in the figure. So the apparatus makes a complete circuit. You can ignore the resistance of the bars and the rails...
  35. JesseJC

    Electromagnetic wave problem

    Homework Statement ⃑E = Eo cos(4.0y−1.2 × 109 t) ̂ (N/C) where y is in meters and t is in seconds. The intensity of the wave is 200 mW/cm2 . (a) In what direction is the wave propagating? (b) What are the wavelength and frequency of the wave? (c) What is the peak value of the electric field...
  36. Rmehtany

    Understanding Lenz's Law and the Right Hand Rule in Electromagnetic Induction

    Homework Statement Homework Equations Not really? I just used the right hand rule and Lenz's law The Attempt at a Solution By the right hand rule, outside of loop 1, the magnetic field is out of the page. However, increasing resistance means that field is weakening. We know by Lenz's law...
  37. kolleamm

    Electromagnetic muscles? Practical?

    Here's my idea for a robotics actuator resembling a muscle. Lots of tiny electromagnets closely packed attracting each other to flex an artificial muscle. It seems like such an obvious idea, why isn't anyone using it?
  38. S

    Semantics Q about electromagnetic spectrum and light

    Kind of a silly question here, but one that has nagged at me for some time: Does the word "light" refer to all wavelengths of the electromagnetic spectrum, or only to the visible light that we can see? Also, if light only refers to visible electromagnetic radiation, then what about ultraviolet...
  39. Ronie Bayron

    B Does Electromagnetic wave qualifies to become a particle?

    Hi, light as an EM wave attributes wave-particle duality. In general, are the other bandwidths of EMW (UV & IR for example) qualifies the same duality? How? Why and why not?
  40. T

    Stratton Electromagnetic Theory Chapter 1 and 2 problem solutions missing?

    Why are there no problems at the end of chapters one and two in Stratton Electromagnetic theory like there are at the end of all the other chapters??
  41. erashish14

    Electromagnetic Induction Help Requested

    Hi Experts, I'm doing an experiment of Electromagnetic Induction (producing current by changing magnetic field i.e. by circulating magnetic wheel of N52 Neodymium Magnets around copper coil), but what i found when the speed of wheel is HIGH, the Output Current is LOW (in range of .02...
  42. M

    Converting Electromagnetic Energy To Temperature

    Homework Statement For a home work assignment, I have to build a theoretical device which uses a laser to boil water. But I have no idea how to figure out how long it would take the device to transfer enough heat to boil the water. The laser diode has a wavelength of 445nm. We are supposed to...
  43. D

    Magnetic Field of Spherical Electromagnetic Wave

    1. The problem statemeent, all variables and given/known data The field electric's electromagnetic wave issued by a strut isotropic source is: \vec{E} = E_{0} r_{0}*cos(ωt − kr) \vec{θ} Find the magnetic field in spherical coordinates Homework Equations I think, i use the equation \vec{B} =...
  44. IndyKuma

    What is the induced current in a resistor due to a moving wire with current?

    Homework Statement A rectangle circuit which has a resistor R and has a size l*w. The circuit is moving away from an infinite long wire which has a current i moving up along the wire with velocity v. Find the current moving in the resistor's side which far from the wire r. Here's the figure of...
  45. E

    Electromagnetic continuity equation

    Hi, this looks stupid and simple, but I just can't get my head around it. Assuming a homogeneous medium. The electromagnetic continuity equation goes as ∇⋅J + ∂ρ/∂t = 0 since J = σE, ρ = ɛ∇⋅E, and assuming the time dependence exp(-iωt) we have σ∇⋅E - iωɛ∇⋅E = 0 (σ - iωɛ)∇⋅E = 0 So, σ - iωɛ = 0...
  46. B

    Why are electromagnetic waves not visible themselves but....

    Why are electromagentic waves not visible itself but visible if they are reflected by an object ? Assuming a source of light emitting photons. This waves are not visible in the dark. If they end up on a surface of any object which "reflects" the light we start to see the object. What happens at...
  47. radio171

    Where do electromagnetic waves get their energy from?

    We know that EMW are generated by accelerating charges. If I accelerate a charge it should gain kinetic energy equal to half the mass of the charge times velocity squared. But at the same time it will radiate electromagnetic waves which carry energy itself. So where does this energy come from...
  48. T

    Why is the electromagnetic field not a 'charge field'

    This question is a continuation/topic-extrapolation of: https://www.physicsforums.com/threads/flux-in-magnetic-core-according-to-special-relativity.856482/#post-5374651 My question is 'how is the electromagnetic field different from some sort of mere electric-charge field?' The issue I have...
  49. K

    Electromagnetic Waves: Electric & Magnetic Fields

    Is it correct to say a varying electric field creates a magnetic field and vice-versa instead of saying that a charge creates such fields?
  50. J

    Electromagnetic waves and polarity

    Say you have a transmitting whip antenna. If you send a quick DC burst into it, you will get the electrons in the antenna accelerating in one direction like this: If that EM wave is then absorbed by a receiving whip antenna, the electrons will also move in one direction. The polarity of the EM...
Back
Top