What is Electromagnatism: Definition and 66 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. B

    Electric field between inner and outer cylinder

    Homework Statement A capacitor is constructed of two long concentric metal cylinders, each having length of 1.0 meters. The inner cylinder has a radius R1 = 1.0 cm, and the outer cylinder has a radius R2 = 1.25 cm. The hollow space between the two cylinders is filled with nylon having a...
  2. B

    Proof that disk of charge = point charge when very far?

    Homework Statement Take the expression 21.11 (pictured below, specifically the bottom one) for the electric field above the center of a uniformly charged disk with radius R and surface charge density σ, and show that when one is very far from the disk, the field decreases with the same square...
  3. J

    Index of Refraction: Calculate ni for 10 cm Attenuation

    Homework Statement Within a certain material, an EM wave with = 1 mm is attenuated to 10% of its original intensity after propagating 10 cm. Determine the imaginary part of the index of refraction ni Homework Equations 3. The Attempt at a Solution [/B] so...
  4. S

    Electromagnetic radiation pressure

    I am confused with the fact of radiation pressure on Wiki and my homework solution. They are both arguing that the pressure produced by a ray of light to be reflected with incident angle θ and intensity I is: $$\frac{2I\cos^2(\theta)}{c}$$ My thinking We know that: $$Ft=\Delta p$$ We see the...
  5. E

    Modes orthogonality in a dielectric slab

    A typical mode in a dielectric slab like this, with propagation along x, uniformity along z and refractive index variation along y, is represented by the following function: f (y) = \begin{cases} \displaystyle \frac{\cos (k_1 y)}{\cos (k_1 d)} && |y| \leq d \\ e^{-j k_2 (y - d)} && |y| \geq d...
  6. S

    Magnetic field of a long solenoid

    Homework Statement A long solenoid has current I flowing through it, also denote N as the turns per unit length. Take its axis to be the z-axis, by symmetry the only component of the magnetic field inside is Bz. Find the magnetic field at the center of the solenoid (on the axis). Also, find the...
  7. S

    Potential inside a sphere with two regions

    Homework Statement Suppose a charge is distributed in a lower half region of a sphere and the upper half has zero charge. What is the potential inside? Homework Equations Poisson Equation? The Attempt at a Solution My problem here is I don't know how to start, I think laplace equation can't...
  8. E

    Wave reflection and refraction, relations between angles

    Hello! This post is strictly related to my previous one. Let's consider the same context and the same image. Regarding the oblique incidence of a wave upon an interface between two dielectric, all the texts and all the lectures write an equation like the following: e^{-j k_1 y \sin \theta_i} +...
  9. S

    Potential inside a grounded conducting sphere

    Homework Statement Hi, I'm currently answering a problem in Jackson's electrodynamics. The question is: Given a point charge q inside a hollow. grounded, conducting sphere of inner radius a. Find the potential inside. This can be solved by placing an image charge outside the sphere, and...
  10. Luminescent

    Who Derived the Value of Magnetic Permeability in a Classical Vacuum?

    Who is credited for deriving the value of magnetic permeabilty in a classical vacuum? How would one go about sourcing information in relation to such a value?
  11. P

    Electrical Potential Energy of three quark system

    Homework Statement A proton is composed of three quarks: two "up" quarks, each having charge +2e/3, and one "down" quark, having charge -e/3. Suppose that the three quarks are equidistant from one another. Take the distance to be 3×10-15 m and calculate the potential energy of the subsystem of...
  12. X

    Determine charge at origin, based on charge density function

    Homework Statement a) and b) are no problem. I need help to solve c) and d) Homework Equations c) Delta dirac function Gauss' law d) Gauss' law ## \int_V {\rho \, d\tau} = Q_{enclosed} ## The Attempt at a Solution By taking laplace on the potential I get: ## \rho(\mathbf{r}) =...
  13. P

    Force at center of cube due to four charges of equal mag.

    Homework Statement Four charges of 2*10^-7 are placed on the corners of one face of a cube of 15 cm. A charge of -2 * 10^-7 C is placed at the center of the cube. What is the force on the charge at the center of the cube? Homework Equations F = k q_1*q_2/r^2 The Attempt at a Solution...
  14. W

    I'm making an Arithmetic Error, Electrostatic force diagrams

    Homework Statement Three charged particles are placed at each of three corners of an equilateral triangle whose sides are of length 2.7 cm . Two of the particles have a negative charge: q1 = -6.0 nC and q2 = -12.0 nC. The remaining particle has a positive charge, q3= 8.0 nC . What is the net...
  15. P

    What Drives the Quest for Quantum Gravity?

    Are the differences between relativity and quantum mechanics due to the difference between gravity and electromagnatism?
  16. U

    Electromagnatism - Find charge deos this sphere have

    Homework Statement The centre of a small sphere carrying a positive charge of 1.0 x 10^-8 C is fixed at 3cm above the centre of a small conducting ball, which had a negative charge and a mass of 0.05g. If the ball remains suspended, what charge does it have? Answer is [ 4.9 x 10^-9] but...
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