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Electromagnetic Optics

A Plain Explanation of Maxwell's Equations

Physical Meanings of Maxwell's Equations Maxwell's Equations are composed of four equations with each one describes one phenomenon respectively. Maxwell didn't invent all these equations, but rather he combined the four equations made by Gauss (also Coulomb), Faraday, and Ampere. But Maxwell added one piece of information into Ampere's law (the 4th equation) - Displacement Current, which makes the equation complete. Gauss's law for static electric fields Gauss's law for static magnetic fields Faraday's law which says a changing magnetic field (changing with time) produces an electric field Ampere-Maxwell's law which says a changing electric field (changing with time) produces a magnetic field The combination of equations 3 and 4...

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Dielectric Strength

Dielectric Breakdown An electric field causes small displacements of the bound charges in a dielectric material, resulting in polarization. If the electric field is very strong, it will pull electrons completely out of the molecules. The electrons will accelerate under the influence of the electric field, collide violently with the molecular lattice structure, and cause permanent dislocations and damage in the material. Avalanche effect of ionization due to collisions may occur. The material will become conducting, and large currents may result. This phenomenon is called a dielectric breakdown.     Dielectric Strength The maximum electric field intensity that a dielectric...

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Electric Dipole

What Is an Electric Dipole? The electric dipole is an important entity in the study of the electric field in dielectric media, which is very important for the analysis of electromagnetic optical waves in waveguides. A system of two equal and opposite charges q separated by a small distance L is called an electric dipole as shown below.   Electric Dipole Moment An electric dipole's strength and orientation are described by the dipole moment , which is a vector that points from the negative charge -q toward the positive charge +q and has the magnitude .   is called the displacement vector pointing from...

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Solution Path for Electromagnetic Problems

There are quite some fundamental equations of electromagnetic theory, which sometimes could be confusing to use. The chart below shows how to approach a problem, evaluate the physical situation, find out boundary values and constraints, and then follow a clear path in order to achieve a solution. Engineers should refer to this chart, which will clarify the steps and procedures.                

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Dielectric Polarization

A dielectric material (dielectric for short) is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material as they do in a conductor, but are displaced from their original positions. Positive charges are displaced in one direction (parallel to the applied electric field) and negative charges are displaced in the opposite direction (antiparallel to the applied field). These displaced charges give rise to their own electric field that opposes the external field as shown below.     This makes the net...

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