Electromagnetism Definition and 853 Threads

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

    Can \(\vec{E} = E_0 \cdot (-y,x, z)\) Be an Electrostatic Field?

    [Mentor's note: this thread was originally posted in a non-homework forum, therefore it does not have the homework template.] ------------ I have a question which is:Let \vec{E} = E_0 \cdot (-y,x, z) Can \vec{E} be an electrostatic field? if yes, find the charge density which generates this...
  2. M

    Motor Principle and Magnet on Balance

    Hi everybody. This is my first thread ever on this forum :S I'm in a first year physics class, and the other day we did a lab involving a c.c.c (current carrying conductor) and a magnet on a balance. The c.c.c was a wire which completed a circuit. One had a magnet assembly which was placed on...
  3. ghost313

    Calculus books to understand physics

    Good morning Everybody and Merry Christmas, Could someone advise me a book they had in the past from which they learned calculus for physics? I am looking for a difficulty level so that I could understand in classical mechanics electromagnetism. I would like to know how to solve every possible...
  4. R

    Slab Beam of electrons through Neutralising Ions

    Homework Statement A slab beam of electrons of thickness a, width w >> a, charge density (-ρb ), (Take ρb to be positive.) and velocity vbez passes through a channel of neutralizing ions with charge density f*ρb where f is some number between zero and one (all parameters given above apply in...
  5. R

    How Are Cathode Rays Deflected by Current-Carrying Wires?

    Homework Statement A cathode-ray tube aims electrons parallel to a nearby wire that carries current in the same direction. What will happen to the cathode rays in terms of deflection? The Attempt at a Solution [/B]The Motor force deflects the cathode rays ?
  6. naima

    How Does the Derivative Term Arise in the Commutator of Electromagnetic Fields?

    I start from these formulas(transverse electric and magnetic fields) ## E_\perp(r) = \Sigma_i i \mathscr E_{\omega_i}\epsilon_i [\alpha_i e^{i k_i . r}- \alpha^\dagger_i e^{-i k_i . r}]## and ##B(r) = \Sigma_i i(1/c) \mathscr E_{\omega_i}(\kappa_i \times \epsilon_i) [\alpha_i e^{i k_i . r}-...
  7. B

    Is B more analogous to D or to E (electromagnetism)?

    In the book I'm reading on electromagnetic fields, the authors seem to associate the magnetic flux density B with the electric flux density D, and the magnetic field H with the electric field E. Now, my question is, wouldn't it make more sense to say B is the analog to E? Because E and B are...
  8. R

    Artificial Magnetic Fields — Electromagnetism (Physics Gr12)

    Homework Statement Two parallel conductors each carry 10 A of current in the same direction. a) What is the magnetic field strength at the midpoint between these wires? (answer = 0T) b) What is the field strength at the same point if the current ran in opposite directions? (answer = 4.0x10^-4T)...
  9. U

    How is the Faraday Tensor related to the 4-potential?

    The Faraday Tensor is given by: Consider the following outer product with the 4-potential: The Faraday Tensor is related to the 4-potential: F^{mn} = \Box^{m} A^n - \Box^n A^m For example, ## F^{01} = -\frac{1}{c} \frac{\partial A^x}{\partial t} - \frac{1}{c}\frac{\partial...
  10. S

    What is the distance at which an antenna can receive signal?

    Homework Statement Assume that the power radiated by the television transmitter uniformly fills the upper hemisphere. A UHF television with a single-turn circular loop antenna of radius 8 cm requires a maximum induced voltage above 24 mV for operation. The speed of light is 2.99792 × 108 m/s...
  11. S

    How Much Power Can a Coaxial Cable Transmit Before Breakdown?

    Homework Statement A coaxial transmission line consists of an inner cylindrical conductor of radius 1mm and a cylindrical outer conductor chosen to make the characteristic impedance 75 ohms. The space between the conductors is filled with a gas that can stand a maximum field of 10^5 Vm^-1...
  12. K

    Upper Limit of EM-Field Strength

    Hello! Which are the highest theoretically possible electric and magnetic vacuum field strengths E and H? How are they calculated?
  13. Dikshant

    Electric Charge and Magnetism: Constant or Varying Magnetic Field?

    If an electric charge is moving with constant velocity,what does it create?? A constant magnetic field or 1 which is varying with time?? What if it accelerate?
  14. S

    What is the magnetic flux through the prism's right side?

    Homework Statement Now, ignore the lengths given in the photo. Height (y) = .640 meters Length (z) = 1.18 meters Base (x) = .320 meters Magnetic Field (B) = 3.5 Teslas in the +X direction Homework Equations The problem is to find the magnetic flux through the surface of the...
  15. J

    Is electrostatics the cause of radio waves?

    That is probably a badly worded question but I understand electrostatics and I want to send simple but efficient radio signals. If I switch on a strong charge in one place it'll effect a charge away from it depending on "Coulomb's law". How is this equation expanded to explain more efficient...
  16. J

    Buy a Radiometry Textbook for 0-10 Miles Wave Generation

    I want to send radio waves through distances of 0 to 10 miles, maybe even hundreds of miles eventually. What book should I buy to educate myself? I am not really interested in doing complicated things with electricity unless it translates directly into something which will improve the...
  17. 2

    Force between two parallel wires carrying current?

    There is something I am confused about when it comes to the force between two parallel wires carrying current, specifically why when they carry current in the same direction the wires are attracted to each other. I understand that when you use Flemming's left hand rule and consider the electrons...
  18. L

    Does this curl operator equal 1?

    Hello, I am a beginner in electromagnetism. I am trying to find a vector field whose rotation equals 1 with a curl operator. If I say that the vector field is defined by V(y;2x;0) does it work? As a result, I find (0;0;1), am I right?
  19. N

    Partial derivative with respect to metric tensor

    \mathcal{L}_M(g_{kn}) = -\frac{1}{4\mu{0}}g_{kj} g_{nl} F^{kn} F^{jl} \\ \frac{\partial{\mathcal{L}_M}}{\partial{g_{kn}}}=-\frac{1}{4\mu_0}F^{pq}F^{jl} \frac{\partial}{\partial{g_{kn}}}(g_{pj}g_{ql})=+\frac{1}{4\mu_0} F^{pq} F^{lj} 2 \delta^k_p \delta^n_j g_{ql} I need to know how...
  20. Alxb577

    Electromagnetics Essay Topic Ideas

    Hi Everyone, I need to write an essay for my electromagnetism class and i was wondering if anyone has good topic ideas. My criteria is that it needs to be 10 pages and I would like something that is interesting for me to research and write about. I was thinking so far of magnetic levitation...
  21. Z

    Detailed Physics of the D.C. Motor

    So I have been curious as to the exact workings of a simple D.C. electric motor, and the transformation of electric energy into motor power. I think I have a basic understanding of the topic but there are numerous gaps in my understanding. Firstly, I think I am correct in saying that as an...
  22. B

    Separation of Variables in 2 Dimensions: A Laplace Equation Primer

    So I'm currently taking electricity and magnetism and I'm expected to know how to perform a separation of variables on laplace equation in 2 dimensions.I have taken Zero differntial equations courses and I literally have no freaking idea what's going on. The book I use doesn't spend any time...
  23. E

    Battery alone deflects compass needle?

    Homework Statement I'm an introductory electromagnetism course and in lab we were observing how an electric current could deflect a compass needle. however, i also noticed that the batter itself (with no wire attached, so no current) could also deflect the needle. (for ex, if you brought the...
  24. E

    Electric surface current on a PEC

    Hello! When considering the boundary conditions for the electromagnetic field \mathbf{E}, \mathbf{H} on the surface of a Perfect Eletric Conductor we have: \mathbf{E} \times \mathbf{\hat{n}} = 0 \mathbf{J}_S = \mathbf{\hat{n}} \times \mathbf{H} the tangential electric field should vahish...
  25. E

    Electromagnetism equivalence theorem

    Hello! In http://my.ece.ucsb.edu/York/Bobsclass/201C/Handouts/Chap1.pdf, pages 19-20, the Love's Theorem in Electromagnetism is declared. In presence of some electric sources \mathbf{J} and magnetic sources \mathbf{M} enclosed by an arbitrary geometrical surface S, which produce outside S a...
  26. T

    About Lorentz force and Lenz' law

    Hello Physics forum, I have come here seeking for some experienced help about a doubt that to some extent is not letting me advance on my studies of electromagnetism. Basically is about the magnetic (B) field, and more specifically, about the force at each point of the vector field (The lorentz...
  27. H

    Electromagnetism and theoretical shape of a photon

    Hello all, I have a few questions and a few thoughts I think I understand that according to einsteins theory of relativity, wavelengths can be perceived differently when traveling at different velocities comparatively to when it was emitted. i.e. if something traveling close to the speed...
  28. J

    As unified electromagnetism derived c, what concepts were unified to h

    I suspect that Quantum Mechanics' true theory would be understood, at least partly, by what Planck's Constant unified, like how the speed of light in vacuum was derived by Maxwell's unification of electricity and magnetism as two manifestations of one fundamental force. So, if some physics-grads...
  29. S

    Questions on electromagnetism

    I would like to know if this formula to convert a magnet's pulling force(lbs) to kGs is correct and reliable. I got it off this website http://www.trentatron.com/landing.htm Pull Force = 0.576 x Br² x (Th) x √‾A where Br = Flux Rating in KiloGauss Th = Thickness of Magnetized Surfaces in...
  30. Dale

    Covariant macroscopic electromagnetism

    I wondered if anyone had a good online reference on the covariant formulation of Maxwell's macroscopic equations and the other equations of classical electromagnetism? The wikipedia article talks about constituitive equations in vacuum, which doesn't make a lot of sense to me since M and P...
  31. Greg Bernhardt

    Exploring Scalar and Vector Flux in Electromagnetism

    Definition/Summary Flux sometimes means total flow through a surface (a scalar), and sometimes means flow per unit area (a vector). In electromagnetism, flux always means total flow through a surface (a scalar), and is measured in webers (magnetic flux) or volt-metres (electric flux)...
  32. A

    Meaning of Dyadic Green Function in Electromagnetism

    I know that in the vector potential formulation one can use a scalar Green function (to find the said potential and from then on the electric and magnetic fields), and that this works because the components of the potential are in the same direction as those of the source - i.e. a current in the...
  33. C

    Index gymnastics of electromagnetism quantities

    This bothers me, and the question is simple: If am working with a non-minkowski metric g, when raising or lowering indexes of electromagnetism quantities, for example the electromagnetic tensor F, or the vector potential A, should I use my curved spacetime metric g or the minkowski metric n?
  34. E

    Learning Electromagnetism before classical mechanics?

    Hi all, So basically I would like to know if it's possible. I'm a first year undergrad and I did classical mechanics first semester but I didn't do that well in it. So I'm not sure if I need to use my holidays to catch up with it before we do Electromagnetism during second semester. I would...
  35. S

    Electromagnetism and Clean Energy

    Hey, currently I am a high school graduate going into college in the fall, but that isn't why I am here. There has been this question eating at the back of my head. Is there some way to induce an electromagnetic field, that could then induce a current in a wire or other some such medium, to...
  36. Y

    Is gravity just electromagnetism?

    Recently, I was pondering over the thought that is most of the elementary particles have intrinsic magnetism, then can gravity be just a weaker form of electromagnetic attraction? But decided the idea was silly. But I googled it later and found this article [removed link to crackpot website...
  37. FysixFox

    Concerning the Classical Electromagnetism and Gravitation Constants

    In classical electromagnetism, Coulomb's constant is derived from Gauss's law. The result is: ke = 1/4πε = μc^2/4π = 8987551787.3681764 N·m2/C2 Where ε is the electric permittivity of free space, μ is the magnetic permeability of free space, c is the speed of light in a vaccuum, and 4π is...
  38. U

    Electromagnetism, calculation of B

    Homework Statement A very big iron plate with the thickness 2h have, far from the plates edges, had a hole with the radius a drilled through it. With respect to the holes axis of symmetry the plate has a magnetization \bar{M} = M_0 \frac{a}{s} \hat{s} where s is the distance from the axis of...
  39. K

    Applications of electromagnetism

    Homework Statement Is the magnetic force the Earth exerts on a compass needle greater than, equal to, or less that the force the compass needle exerts on Earth? Explain. Homework Equations None. The Attempt at a Solution I attempted to analyze the forces as if they behaved as...
  40. K

    Analogy between fluid dynamics and electromagnetism

    I've recently heard of an analogy between fluid dynamics and electromagnetism in which the velocity flow field is identified with the magnetic vector potential, (and therefore the vorticity is identified with the magnetic field), and the vector \omega \times v is identified with the electric...
  41. johann1301

    Electromagnetism and relativity

    In a video on the youtube channel "Veritasium", it is explained that an electric field and a magnetic field is basically the same thing, it all just depends on which reference frame you are observing it from. The video demonstrates that if a positive particle is traveling along side of a wire...
  42. P

    The continuity equation in electromagnetism

    I understand the reasoning behind the equations ∫SJ.dS=-dQ/dt and thus ∇.J=-∂ρ/∂t. where the integral is taken over the closed surface S. However I'm a little confused about the conditions of steady currents: The book I'm using sets dQ/dt=0 and ∂ρ/∂t=0 in these cases. I don't understand this...
  43. J

    Electromagnetism: find the laplace force

    Hi every one. Homework Statement in french,the problem says:"déterminer la force de laplace qui s'exerce entre deux fils de courants réctilignes,indéfinis,parraléles d'intensités I et I' de meme sens".maybe in english it means:"find the laplace force that is applied between two...
  44. M

    Gauss Law: Proofs and Electromagnetism Resources

    about gauss law! is there any precise proof for gauss law? why ø=q/ε always regardless how the charge is distributed inside the surface and if anyone know a good book for electromagnetism please type its name for me.. thank u
  45. K

    Replacing the current by the fields in electromagnetism.

    hello, In electromagnetism from the Lagrangian formulation, one can defines a canonical momentum and applying Euler's equation to that momentum gives the lorentz law. To get the Lorentz law, one uses a vector identity, only available because it is said the speed V does not 'feel' the...
  46. S

    Electromagnetism and Beta Decay

    Hello! I am participating in a STEM fair(I am a middle schooler), and my scientific question is : Does the angle of the particle trails increase from beta decay when you introduce an electromagnetic influence? I have been at a loss for finding a helpful site. The ones that I have come...
  47. R

    Integrating a vector (Electromagnetism)

    Homework Statement Given \textbf{E}(z,t) = E_{0}cos(kz+ωt)\textbf{i} Find B Homework Equations ∇ x E = -\frac{\partial\textbf{B}}{\partial t}The Attempt at a Solution Taking the curl of \textbf{E} gives (0, -ksin(kz+\omega t), 0) so \frac{\partial\textbf{B}}{\partial t} = (0,ksin(kz+\omega...
  48. J

    Electromagnetism Electromagnetic fields

    Hi all, can the angular frequency of a electric waves be used to determine the wavelength using the following; ω=2πf rearranging for the frequency, and using the following; E=hf=(hc/λ) or can this formula no be used as it is dealing with photons?
  49. J

    Electromagnetism electric fields

    An Electric field has the following form in free space; E=Re{Eo exp[j(ωt-κy)\hat{i} I am confused as to why a unit i vector is in the expression for an electric field oscillating in the Y direction? and also what does the Re mean ? i was reading somewhere about it being to do with...
  50. J

    Electromagnetism, dynamics and energy

    a 17KG cat is shot out of a hole in the side of a charged plate when the voltage is suddenly turned up to 5000V. The cat has a charge of 2.377^16c. He lands in a 3kg crate on wheels that has a µ=0.1 for o.50 meters. The crate is then put to stop by a spring 700 N/M. how much did the spring compress?
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