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. C

    Improve Your Understanding of Electromagnetism with These Recommended Textbooks

    Hi all, Just got a quick question regarding textbooks revolving around electromagnetism studies. I'm a Mechanical Engineering major and I have a firm grasp on pretty much all classical mechanics and have begun exploring some quantum studies for personal pleasure. I've found however that I am...
  2. E

    How Does the Speed of a Van Affect the Lorentz Force in a Magnetic Field?

    Homework Statement Problem is http://imgur.com/bQIFJ Homework Equations I presume F=BIl and E=Blu. The Attempt at a Solution Not very well. I don't really understand how to start the question so if I could get some nudges in the right direction that'd be great. I'm not sure how...
  3. E

    Electromagnetism - intrinsic impedance and poynting vector

    1. I know that 1/2 of the real part of the complex poynting vector gives the average power flow per unit area. But what is the significance of its imaginary part ? 2. What is the significance of the complex intrinsic impedance ? For lossless medium (i.e. with no ohmic losses) it is real , but...
  4. R

    Electromagnetism Problem (conductors, dielectrics)

    Homework Statement http://img209.imageshack.us/img209/1508/problemhd.jpg Homework Equations The Ampere law: \oint_C \vec{B} \cdot d\vec{l} = \mu_0 I_{enc} The field and flux is proportional to the current: \Phi = LI The Attempt at a Solution (a) \oint_C \vec{B} \cdot d\vec{l} = \vec{B}...
  5. A

    Gravity - relationship with Electromagnetism?

    Gravity -- relationship with Electromagnetism? Hi all my interest in Physics is purely a hobby and I have to say I have gaps in my knowledge but even then I have a question is it possible that the wave and particle nature of electromagnetic waves and small particles are related to gravity...
  6. A

    Question about electromagnetism

    Is electromagnetism a combination of electricity and megnetism; hence "electro-magnetism"?
  7. N

    Electromagnetism & Higgs Boson

    I want to get caught up in this discovery and of course it would more "legitimate" if I better understood what the standard model is.So I'll ask some slightly random "Yes/No" questions. Are the "Gauge Bosons/Force Carriers" that have mass "supposed to be" mass-less? But from...
  8. S

    What is the relationship between light and electromagnetism?

    So how is light related to EM-ism? I can understand its relation to heat and materia to a certain extent. But overall the magnetic field does not have any effect on a common ray of light. And i cannot magnetise ,for example, a piece of iron just by showering it with a light of a certain...
  9. I

    Can someone explain electromagnetism?

    I know its mediating boson is the photon, but i don't understand how that works. Wikipedia is no help, so i hope you guys can. How can the particle of light (even though it is oscillating electric and magnetic waves) which is neutral in charge, affect anything with an electric charge? Say...
  10. M

    Electromagnetism question involving two stationary conductors and crossbars

    Homework Statement Question and diagram below Homework Equations F=BIL F=QVB Vback=(epsilon)-Ir The Attempt at a Solution F=QvB ma=QvB QvB/m=a ? I really don't know how to start this question.
  11. M

    What is the Brewster Angle for Circularly Polarized Light?

    Homework Statement Hello everybody. I have a big problem with this important problem that i can't solve and i have no solution ... A circularly polarized monochromatic wave is reflected from a dielectric mirror which has parameters μ and ε. Its wave vector is k = (k0, 2k0,0). Find the magnetic...
  12. S

    Is My Approach to Deriving Quantities for a Charged Sphere Correct?

    Hey, I have a series of questions on a basic charged sphere and deriving quantities such as the infinitesimal charge, the total charge and the electric field. The question is part (b) in the image below: So I found dQ' by equating it to the surface area of a shell at a distance r'...
  13. S

    What is the Poynting Vector for a Time-Dependent Electric Field in Vacuum?

    3 (a) ii) A time-dependent electric field in vacuum is given by ⃗E= E0(0, 0, sin(ky − ωt)) where E0 is a constant. Derive an expression for the corresponding magnetic field ⃗B. [7] Using curl E=-dB/dt I end up with B=(E0/c)sin(ky-wt) Show that both ⃗E and ⃗B are perpendicular to the wave...
  14. F

    Ignoring the sign of a charge in electromagnetism

    Homework Statement I just did a question on a charge moving relative to a stationary charge from an initial position x1 to a final position x2. I was under the impression that for questions involving coulombs law, and the equations for Electric Field Strength, Force and Potential we ignore any...
  15. A

    Question about electromagnetism

    Wat is meant by "interference" in "electromagnetism is the interference between the electricity and magnetic force."?
  16. N

    No graduate level electromagnetism? (Oh Jackson where art thou)

    Next year I'm doing the one year master program at Perimeter Institute, and I was surprised to realize that there is no grad-level electrodynamics class (level Jackson, I would suppose?). I then checked the Math Tripos III (applied math, aka theoretical physics) course list (where I also...
  17. M

    Electromagnetism - Cross Product of length and Magnetic Field

    Homework Statement A stiff wire 42.0cm long is bent at a right angle in the middle. One section lies along the z axis and the other is along the line y=2x in the xy plane. A current of 15.0 A flows in the wire-down the z axis and out the line in the xy plane. The wire passes through a uniform...
  18. S

    Intensity in Electromagnetism versus probability density in Quantum Mechanics

    In the book Introduction to Quantum Optics: From the Semi-classical Approach to Quantized Light by Grynberg, Aspect and Fabre I came across the following statement on page 385: "By the end of the nineteenth century, classical electromagnetism,..., provided a wave description of almost all...
  19. J

    Help with simulation in ANSYS Maxwell, 3D electromagnetism simulator

    Hello, I'm currently conducting a very serious high school research project titled: Maximizing Energy Efficiency of a Linear Electromagnetic Accelerator I have recently been bestowed with a temporary license for a very advanced 3-dimensional electromagnetism simulator that should allow me...
  20. V

    Spaghettification electromagnetism

    I posted this question on another forum, and, the answers, thus far, have not really helped me out very much. So, I figured physics questions are best directed toward the 'physics guys'. Here is the text of my two posts. I feel like the problem probably lies with my extremely limited...
  21. C

    Electromagnetism problem-ΣE on a point

    Homework Statement Hi. I need help with the problem attached. I need to find the ΣE of the point and the direction angle... All information needed are on the attachment... [b]2. Homework Equations [ The Attempt at a Solution There is no attempt since the teacher said nothing...
  22. N

    Electromagnetism: Direction of B-field

    Homework Statement Hi I have a current loop (see attached), and I have found the expression for the B-field along the axis of the loop. A particle moves through the loop, as also shown in the attached picture. Using the right hand, I let current run through the loop counter-clockwise, shown as...
  23. P

    Nit-Picky Questions on Induced EMF, and Electromagnetism in General

    I just need some clarification on the induced EMF Formula.. I know that the negative sign in front of N * dFlux/dt is just an indicator of Lenz's law, but if we were given the magnetic flux as a function of time, would there be situations where -d/dt(F(t)) would be different than just...
  24. S

    Calculating Speed of a Charged Particle in Electromagnetism

    A 5.0nC point charge travels in a circle of radius 1.0cm. What is its speed so that the current it generates 1.0mA?. I tried to use I=nqvA, but for some reason it didnt work because i don't know how to calculate n. any hints? thanks!
  25. T

    Electromagnetism with Lentz's Law

    Homework Statement A rectangular loop of wire resistance R and dimensions h and w moves with a constant speed v toward and through a region containing a uniform magnetic field of strength B directed into the plane of the page. The region has a width of 2w as shown above. (I think our teacher...
  26. S

    Difference between electromagnetics and electromagnetism ?

    I have come across books titled "engineering electromagnetics" and "electromagnetics with applications" but I could never find a page for electromagentics on Wikipedia. However, there are pages for electrodynamics/electromagnetism/electrostatics on Wikipedia. Is there a difference? If so what...
  27. D

    Electromagnetism - Motor Question

    Hi, I have a very basic question. When a current carrying rectangular loop of wire is kept parallel to a magnetic field there is a torque in the loop of wire causing it to rotate. I was wondering what causes it to rotate further when the rectangular loop of wire is perpendicular to the...
  28. X

    Electromagnetism: Possible Trick Question?

    The nature of this problem seems like it is elementary E&M, but it is in my graduate electromagnetism class so I didn't know the proper section to post it. Homework Statement Two small conducting spheres have charges of 2x10^-9 C and -0.4x10^-9 C. a.) When they are placed 4 cm apart what is...
  29. G

    What is the Total Energy in a System of Free and Bound Charges?

    Homework Statement Consider a system of “free” charges {qi } and “bound” charges {Qi }. Both types of charges feel the Coulomb force due to all other charges (free and bound). However, the bound charges feel additional “mechanical” forces due to the other bound charges. Let the mechanical...
  30. S

    [Electromagnetism] How much work is required in moving Q3 to infinity?

    Homework Statement How much work is required in moving Q3 to infinity while Q1 and Q2 remain in their positions? Q3-------a-------| |-----------------| b Q1-------------Q2 a = 16.0 cm b = 6.0 cm Q1 = 5.70 μC Q2 = -5.70 μC Q3 = 1.8 μC Homework Equations W=ΔPE PE=kQ1Q2/r...
  31. D

    What books to learn Electromagnetism?

    Hi, So I'm studying Electromagnetism this semester, and my professor held up four books for us to get to study from. I know for sure one was Feynman's lectures, and one of the others he said was the 'Bible' for E&M (expensive, only comes in hard cover, I believe was green...). The thing...
  32. M

    Calculating Electric Flux of Displacement Vector w/ Cylindrical Co-ords

    Using cylindrical co-ordinates (r, theta, z), calculate the electric flux phi=integral D . dS when the displacement vector D is given by: D=10ezcos(theta)/r2 . kr + z2sin(theta)/r2 . Kz and the surface S is part of a cylinder of radius a=0.3, defined by 0 is less than or equal to z which is...
  33. H

    Electromagnetism test preparation for grade 12

    i'm currently taking grade 12 physics. my teacher is really nice, but i got say that she sucks at teaching, and the textbook we're using is worse. can anyone here help me with understanding the basics theories and equations I need for this test?
  34. A

    Force Carrier for Electromagnetism

    Can anybody give me or point me to a model that describes how electromagnetism works from a photon force carrier perspective. I like to know how the virtual photons are generated around an electron. Also why electromagnetism is polar. I am also confused why moving electric fields create magnetic...
  35. N

    Rigorous introduction to electromagnetism

    I'm looking for a good introductory text on electromagnetism for someone who has very little experience with physics but is comfortable with multivariate and vector calculus and ODE's. I'd prefer something that starts from the basics and works up in a rigorous fashion. Note that I am proficient...
  36. N

    How Can I Best Prepare for My Second Semester in Electromagnetism?

    I would like to prepare for my second semester of physics in electromagnetism. Its exciting because its my first taste of physics that isn't all about kinematics and dynamics. What are good ways to prepare for electromagnetism? I don't want a rudimentary and superficial understandings. I...
  37. C

    What is the significance of velocity in relativistic electromagnetism?

    I have read: F=q(v*B) where q=charge of the particle v=velocity of the charge particle B=magnetic flux density F= force experienced by the charged particle Now,I could not understand what is the velocity v with respect to? Please help me.
  38. S

    Electromagnetism: Dugdale vs Griffiths

    I need to self-teach myself electromagnetism, and both of these books have been recommended to me. Essentials of Electromagnetism, by Dugdale https://www.amazon.com/dp/B000PY3WG0/?tag=pfamazon01-20 Introduction to Electrodynamics, by Griffiiths...
  39. L

    Electromagnetism - Boundary conditions for Polarization field at interface

    Not actually a homework question, this is a question from a past exam paper (second year EM and optics): Homework Statement Use a Gaussian surface and Amperian loop to derive the electrostatic boundary conditions for a polarization field P at an interface between media 1 and 2 with...
  40. sankalpmittal

    Understanding Electromagnetism: Clarifying Concepts for Class 10th Students

    Some concepts need clarification. I am about to complete my 14 years and am in class 10th. 1. From my textbook : Take a magnetic needle freely pointing in north-south direction. Hold a thick insulated copper wire connected to battery above magnetic needle and close the circuit. It is observed...
  41. K

    Electromagnetism - Potentials due to point charge and along line of of charge

    Homework Statement Consider an infinitely long and thin line of charge, with density 8nC/m. Calculate the electric potential difference ((phi)1-2) between two points in air at radial disances 1mm and 3mm.Homework Equations I am assuming: Phi(r) = λ/2(pi)ε0 * ln(rR/r) where rR is a reference...
  42. F

    3D Visualization of Electromagnetism

    I would like some help in visualizing electromagnetism in three dimensions. I have researched extensively and have come up with nothing but sine waves and pond ripples. But just like sine waves representing sound, which are three dimensional compression waves, do not represent how sound...
  43. D

    Textbook Suggestion: Electromagnetism

    Hello all, I'm looking for some suggestions for textbooks regarding electromagnetism. I want something that goes in depth and really provides the concepts required to actually understand electricity and magnetism. Any Electrical Courses that I am taking are all circuit analysis... Regards, D.Can...
  44. W

    Deriving Electric Field Inside and Outside an Infinitely Long Charged Cylinder

    Not sure if this is advanced. Highly doubt it but oh well 1. Homework Statement Consider an infinitely long charged cylinder of radius R, carrying a charge whose density varies with radius as ρ(r) = ρo r. Derive expressions for the electric field (a) inside the cylinder (i.e. r<R), and (b)...
  45. W

    What is the Electric Field of a Charged Cylinder with Varying Density?

    Homework Statement Consider an infinitely long charged cylinder of radius R, carrying a charge whose density varies with radius as ρ(r) = ρ_{o} r. Derive expressions for the electric field (a) inside the cylinder (i.e. r<R), and (b) outside the cylinder (i.e. r>R). Homework Equations...
  46. H

    Electromagnetism problem using Gauss's Law

    Homework Statement Using Gauss's law calculate the electric field everywhere for the infinitely long insulating cylinder of radius R and charge density of rho = 3r^2(nc/m^3). SHOW ALL YOUR WORK INCLUDING DIAGRAMS. Homework Equations I am lost. The Attempt at a Solution I don't...
  47. P

    Are Electromagnetic Fields Equal in Different Frames?

    Hello. Here is the problem: A charge q is moving at speed v0 to the right in the lab frame. At t=0 the particle passes at the origin (0,0,0). calculate the field at (-d,0,0) at the instant it passes the origin, both in the lab frame and in the charge frame. are they equal? My solution: In the...
  48. K

    What is the Maximum Deflection of a Galvanometer in an Electromagnetic Setup?

    Homework Statement 2 coils are placed side by side without touching. One of them (P) is connected to a galvanometer while the other (S) is connected to a variable resistor and a cell. There's a switch at S and it is open. The resistance of the rheostat is set at its lowest and then the switch...
  49. S

    Which Electromagnetism Problems Should I Focus on for a Basic Understanding?

    Hi there PF I am doing a self-study on electromagnetism based on "Introduction to Electrodynamics" by David Griffith. I am through with chapter 1, where I have solved all the problems. This has taken quite some time, so I want to ask, if anyone could give me some advice, about which problems...
  50. S

    Electromagnetism: Finding Electric Field of non Uniform Charged Rod

    Homework Statement Here is the question: Thin rod AB has length l=100 cm and total charge q=37 nC that is distributed in such a way that its line density ? is proportional to the square of the distance from the end A, i.e. ?(x) =kx^2. Determine electric field E at the end A of the rod. ...
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