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. R

    What is the Total Force on a Wire Segment in a Uniform Magnetic Field?

    1. "A wire segment carries a current of 1.8A from a to b. There is a uniform magnetic field of 1.2T acting in the z-direction. Find the total force on the wire and show that the total force is the same as if the wire were a straight segment from a to b". I've attached the diagram showing what...
  2. L

    Calculating Electrostatic Energy for a Uniformly Charged Sphere?

    A sphere of radius R has a unifromly distributed charge Ze inside it (essentially it's a model of a nucleus) now my tutor worked through the first part of the question with me and we established that the potential inside the sphere was \varphi(\mathbf{r})=-\frac{Zer^2}{8 \pi \epsilon_0...
  3. N

    Electromagnetism question (Stump book) - Dielectric

    Ok this book is very common. It's the question number 6.5 A dielectric object that has a quasi-permanent polarization when the applied field is 0 is called an electret. Consider a uniformly polarized electret in the shape of a cylinder of height h and radius 10h. The polarization in the...
  4. J

    Electromagnetism and Polarisation question

    Homework Statement When a uniform electric field is applied to diamond, the induced dipole moment per unit volume (ie. polarisation) is P_{0} = 1.5 \times 10^{-7} \text{C m}^{-2}. Given that the density of diamond is 3500 \text{kg m}^{-3}, 1 kmole of diamond has a mass of 12kg. Avogadro's...
  5. N

    Exploring the Relationship Between Spin and Magnetism in Subatomic Particles

    Dunno whether this is the right place for this question! but As it is related to subatomic particles, I think it is! We know that magnetism arises due to rotation of an electron around its own axis in metals, but after all what happens due the moving electric current? Will the same...
  6. C

    What Is the Current in a Rotating Electron Model of a Hydrogen Atom?

    Hi I have tried the question below. However I am failing at the first hurdle part a! Some help and advice would certaintly be appretiated. Thanks Taking a simple model of the hydrogen atom as an electron rotating around the nucleus in a circle or radius 0.53ee-10m at a frequency of...
  7. S

    Electromagnetism, vector calculus.

    Hey i was wondering about a paticular problem i found in a textbook. Specifically just one little niggle i have with it. i am given that the electrostatic potential energy in a region of space is given by v(r) = ((q*n)/(epsilon-0))(x^2+y^2) (where n is a constant of dimensions m^-3)...
  8. H

    What is good way to prepare for graduate Electromagnetism

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  9. K

    Is \(\vec{\nabla}^2 \vec{E}\) a Dot or Vector Product?

    Is \vec{\nabla^{2}} \vec{E} a dot or a vector product?
  10. K

    Electromagnetism Homework Help: Gauss & Coulomb Laws for Flux Calculation

    Hi, got some homework to do in electromagnetism and one of the problems is: Homework Statement Consider a Cartesian coordinate system with charges Q (Q = 15μC) at x = + and – 1.3cm, and at y = + 1.7cm and – 0.7cm and at z = + 2cm and -0.5cm. Calculate the flux of the electrostatic field...
  11. C

    Does the difference in charge play a role in electromagnetism such as

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  12. C

    Electrodynamics vs. Electromagnetism: On the use of either term

    I am curious to hear people's opinions and to run a poll on the use of the term electrodynamics vs. the term electromagnetism. Which do you prefer; why? Are there instances where you would use one over the other? Etc? To start off: Some like the use of electromagnetism when speaking of the...
  13. J

    Classical Electromagnetism: Question on Ampere's Law and Displacement Current

    Hi, just out of curiosity... Ampere's Law describes that an electric current produces a magnetic field. When corrected with Maxwell's displacement current, it describes that a magnetic field is also created by a time-varying electric field. Does this mean that an electric current produces...
  14. D

    Help with electromagnetism problem

    Homework Statement An airplane with a wingspan W = 30 m is flying due north at v = 672 km/h. The Earth's field is 1.210-4 T, due north and inclined q = 42 below horizontal. What is the magnitude of the potential difference between the ends of the wings...
  15. C

    How Do You Solve an Electromagnetism Problem Involving a Cylindrical Conductor?

    Hello, I'm new on this forum :) I seriously need help with this problem. It has to be perfect if I want to pass the course, so I will really appreciate any solution to check my results. ---- An electrical current of 100[A] runs through a cilindrical conductor (radius 0.01[m], infinite...
  16. A

    Electromagnetism, calculate electron charge/mass ratio

    [SOLVED] Electromagnetism, calculate electron charge/mass ratio I've spent all day writing a post and now I can't post a link to my picture due to your rules. Solved the problem anyway
  17. S

    Monstrous electromagnetism question.

    [SOLVED] Monstrous electromagnetism question. Homework Statement A slope variable: thèta Amount of coils: 10. Cilinder: Diameter D Length L Massa M Magnetic field B. The cilinder has 10 coils wrapped around it, in rectangular form (over the top and bottom of the cilinder). It is...
  18. A

    Electromagnetism, force between dipole and grounded plane

    Homework Statement An electric dipole is located at a certain distance from a grounded plane. What force does the dipole exert on the plane? (The answer is to be expressed as an equation. No data were given, only the above text) Homework Equations I am not sure about this, but the course is...
  19. P

    Electromagnetism - Need Help for Test

    I know I'm suppose to use the equation F = (kq1q2)/r^2 I tried doing [.1/sq. root (2)] m for two of the forces and just .1 m for one. I plug all the numbers into the equation and add up the 3 but it doesn't work. I really have no clue what to do with this. Please help.
  20. R

    Electromagnetism and Feynman diagrams

    1. Feynman says all of electromagnetism follows from Maxwell equations. 2. Somebody (Pointing to a Feynman diagram of a photon/electron reaction) said all of electromagnetism is in that one diagram. So, can anyone help me with these two questions: how does point 1 come from point 2. And, how...
  21. Greg Bernhardt

    Classical Electromagnetism: An intermediate level course

    A complete set of lecture notes for an upper-division electromagnetism course. The course concentrates on the derivation, properties, and uses of Maxwell's equations. Topics covered include electrostatics, dielectric and magnetic media, magnetic induction, electromagnetic energy and momentum...
  22. qspeechc

    Electromagnetism Books: Affordable 2nd Year Options

    Could someone please recommend a book for 2nd year Electromagnetism? The topics to be covered are: Vector calculus (div, grad, curl), electrostatics, special techniques for potentials, electric fields in matter, magnetostatics, Magnetic fields in matter, current, Ohm's law, circuits...
  23. D

    Electromagnetism Homogeneous Wave Equation

    I've managed to derive from Maxwell's equations the homogeneous electromagnetic wave equation with respect to the magnetic field. (The one that goes Del Squared of H minus (The second order partial derivative of B multiplied by the recipricol of C squared all equal to zero) Hopefully that...
  24. K

    How Does Decreasing Magnetic Field Affect Ammeter Reading in a Circuit?

    Homework Statement -------/\/\/\--------- I X X X 10 Ohm X X XI I X X X X X X X X X XI I X X X X X X X X X XAmmeter I X X X X X X X X X XI I--------il-----------I ...5V Length=10cm and width =10cm R=10 Ohms V=5 volts decreasing magnetic field at rate 150T/s (into the page) What is the...
  25. T

    How Do Electric Fields Differ Between Plasma and Vacuum Sheaths?

    A plasma is described by the dielectric function \epsilon (\omega) = \epsilon_0 (1-\frac{\omega_p^2}{\omega^2}) where \omega_p is a constant. Any attempt to establish a voltage V(t) = V cos \omega t across the plasma generates a region of vacuum called the "sheath" on either side...
  26. dontdisturbmycircles

    Is Griffiths Electromagnetism understandable for first year students.

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  27. J

    Is Zee's Notation for Electromagnetism Standard?

    In A. Zee's quantum field theory in a nutshell he assumes familiarity with Maxwell's lagrangian \mathcal{L} = -\frac{1}{4}F_{\mu\nu}F^{\mu\nu} where F_{\mu\nu} = \partial_\mu A_\nu - \partial_\nu A_\mu with A the vector potential. Although I've seen the magnetic vector potential, I've never...
  28. S

    Electromagnetism Problem, electric charge per unit volume.

    Homework Statement The atmostspheric electric fields at heights of 100m and 1000m above the surface of the eartg are 110 v/m and 25 v/m respectively and are directed downwards. Evaluate the averge electric charge per unit volume in the atmostsphere between these heights. Express your result...
  29. H

    Relativity and Electromagnetism

    Situation A positive test charge q is moving parallel to a current-carrying wire with velocity v relative to the wire in frame S. It is assumed that the net charge on the wire is zero and that the electrons in the wire also move with velocity v in a straight line. The leftward current in the...
  30. H

    Use of Complex Numbers in Electromagnetism.

    I read in an article that the theory of Electromagnetism makes use of Complex Numbers. How are the tools and tricks of Complex Numbers used in Electromagnetic theory. I just wanted to understand the basics of this connection of Complex Numbers and Electromagnetism and figure out if this...
  31. A

    Electromagnetism - right hand rule

    Homework Statement A proton traveling at a speed of 3.0 x 10^6 m/s travels through a magnetic field of strength 3.0 x 10^-3 T, making an angle of 45 degrees with the magnetic lines of force. What force acts on the proton? Homework Equations F = QvB The Attempt at a Solution I...
  32. S

    Some q's about electromagnetism

    I have a few questions about electromagnetism that no matter how many texts i read i can't seem to figure out, so i'll cut to the chase. 1) why is current in the opposite direction of the flow of electrons? Shouldn't it be in the same direction as the electrons are travelling? 2) How does...
  33. C

    Relativistic electromagnetism problem

    Homework Statement Hi to everyone! I would like you to help me for a problem of classical electrodynamics. I have to study the relativistic motion of a charged particle in a coulombian field with center in the origin of the cartesian axes. I have to study the case in which the initial...
  34. L

    How can I create an effective electromagnetism project for my physics summative?

    I need to make a project for my physics summative (gr 12); and I am leaning towards electromagnetism... since my attempt in making a generator failed - and I paid a lot for the magnet and wires. I was thinking of making http://www.bizarrelabs.com/mag2.htm That... but then I'm wondering if...
  35. S

    Question about electromagnetism

    I have one question. It is about current in conductor. It is about electromagnet induction. So I move the magnet among conductor in closed circular loop, like on this http://www.imagehosting.com/show.php/710601_untitled5.bmp.html" So is the way of moving of the electrons depends from the way of...
  36. 2

    Problems involving electromagnetism

    Homework Statement In problems involving electromagnetism it is often convenient and informative to express answers in terms of a constant, x, which is a combination of the Coulomb constant, k, the charge of an electron, e, and H=h/(2pi), with h being Planck's constant. For instance, the...
  37. F

    AP Physics B help - Electromagnetism

    Hi, I've been working on a review assignment for a while, and I"m very good at electricity, so this question has me stumped. Specifically, the 2002 AP Physics B, #3. Two lightbulbs, one rated 30 W at 120 V and another rated 40 W at 120 V, are arranged in two different circuits. (a) The...
  38. A

    Why Does a Metal Ring Heat Up in a Changing Magnetic Field?

    If you place a metal ring in a region in where a magnetic field is rapidly alternating, the ring may become hot to your touch. Why? Is it because a changing magnetic field can create electric fields? I AM SO CONFUSED...and it seems so simple?!?
  39. L

    Electromagnetism: Turning effect of coil

    Homework Statement This is a question about turning effect on a current-carrying coil lying between the poles of a magnet. Please refer to the following link: http://img11.picsplace.to/img.php?file=img10/22/N1_000.gif On the textbook, it is stated the turning effect on the coil can be...
  40. A

    Electromagnetism - Magnetic flux between infinite wire and rectangular loop

    Homework Statement The figure shows a rectangular wire loop, around which a current I flows, and and an infinite straight wire. The wire lies in the plane of the loop and is parallel to, and a distance d from, the side AB. (see attachment) Show that the amount of magnetic flux generated...
  41. B

    Manual Solution for D.K.Cheng's Field & Wave Electromagnetism

    does anyone have manual solution for field and wave electromagnetic by D.K.Cheng?If you do please send me via <jafarianjelodar.ali@gmail.com> THANKS
  42. T

    What Are the Best Budget-Friendly Electromagnetism Books for Beginners?

    Are there any good introductory electromagnetism books that don't cost too much? I'm interested in relativity but I would like to back up and gain a more solid foundation in electromagnetism first. I would like something modern, somewhat rigourous(mathematically), and preferably with a...
  43. A

    Electromagnetism - Lorentz Force

    Homework Statement A particle of charge q starts from rest at the origin of coordinates in a region where there is a uniform electric field of strenth E parallel to the x-axis, and a uniform magnetic field B parallel to the z-axis. Find the equations of motion, and solve them to show that...
  44. A

    Electromagnetism - Conducting Spheres and their potential

    Homework Statement Two hollow concentric conducting spheres hold charges Q[1] and Q[2] as shown in the attachment. Find the potential of each sphere, and the potential difference. Homework Equations Potential difference V = Phi[2] - Phi[1] The Attempt at a Solution I'm having...
  45. A

    Electromagnetism II - Potential and Electrical Field of a Spherical Shell

    Homework Statement Consider a thin spherical shell having surface charge density σ, and radius a as shown in the diagram (see attachment). Find, by integration over the sphere, the potential at a point P, a distance r fromthe centre of the sphere, for r > a. Using this result also find...
  46. D

    Why Does Changing Magnetic Field Direction Affect Current in a Wire Loop?

    Homework Statement A loop of wire of aream 0.32m^2 is palced in a 0.75 T magnetic field. The magnetic field is changed to 0.35 T in the opposite direction in 0.45 s . What is the magnitude of the current through the 15 ohm resistor. Homework Equations emf = -N (flux / time) The...
  47. A

    How Do Moving Conductors and Coils Interact with Magnetic Fields?

    Homework Statement 1) The coil of a moving-coil loudspeaker has a mean diameter of 30mm and is wound with 800 turns.It is situated in a radial magnetic field of 0.5T. Calculate the force on the coil, in Newtons, when the current is 12mA. 2)Explain what happens when a long straight...
  48. P

    Electromagnetism issues need clearing up

    In electromagnetism, when there is an emf is induced in a secondary coil from a current flowing in a nearby primary coil (such as in a transformer), then how is the mutual inductance, number of turns of each coil, the current in the primary coil, and the emf in the secondary coil related...
  49. P

    Electromagnetism books that are good

    I'm looking for something that covers similar material to Electromagnetism, Grant and Phillips (Manchester Physics Series), but is shorter and easier to read through - I find Grant and Phillips useful (and will buy it), but could really do with a summary/outline to build on. Any...
  50. A

    Some questions regarding Electromagnetism

    Hello, this is my first post on these forums, and I hope to get a response. I am doing an experiment about building a type of an amusement park ride on a much smaller scale, and I have some questions and need some advice. Firstly, when I make an electromagnet by wrapping a piece of metal with a...
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