Portal:Electromagnetism
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Electromagnetism is the physics of the electromagnetic field: a field, encompassing all of space, which exerts a force on those particles that possess the property of electric charge, and is in turn affected by the presence and motion of such particles. The term electrodynamics is sometimes used to refer to the combination of electromagnetism with mechanics, and deals with the effects of the electromagnetic field on the dynamic behavior of electrically charged particles. Electromagnetism encompasses various real-world electromagnetic phenomena.
In physics, a magnetic field is the relativistic part of an electric field, as Einstein explained in 1905. When an electric charge is moving from the perspective of an observer, the electric field of this charge due to space contraction is no longer seen by the observer as spherically symmetric due to non-radial time dilation, and it must be computed using the Lorentz transformations. One of the products of these transformations is the part of the electric field which only acts on moving charges - and we call it the "magnetic field".
The quantum-mechanical motion of electrons in atoms produces the magnetic fields of permanent ferromagnets. Spinning charged particles also have magnetic moment. Some electrically neutral particles (like the neutron) with non-zero spin also have magnetic moment due to the charge distribution in their inner structure. Particles with zero spin never have magnetic moment.
James Clerk Maxwell (13 November 1831 – 5 November 1879) was a Scottish mathematical physicist, born in Edinburgh. Maxwell developed a set of equations expressing the basic laws of electricity and magnetism as well as the Maxwell distribution in the kinetic theory of gases. He was the last representative of a younger branch of the well-known Scottish family of Clerk of Penicuik.
Maxwell had perhaps one of the finest mathematical minds of any theoretical physicist of his time. Maxwell is widely regarded as the nineteenth century scientist who had the greatest influence on twentieth century physics, making contributions to the fundamental models of nature. In 1931, on the centennial anniversary of Maxwell's birthday, Einstein described Maxwell's work as the "most profound and the most fruitful that physics has experienced since the time of Newton."
Algebraic mathematics with elements of geometry are a feature of much of Maxwell's work. Maxwell demonstrated that electric and magnetic forces are two complementary aspects of electromagnetism. He showed that electric and magnetic fields travel through space, in the form of waves, at a constant velocity of 3.0 × 108 m/s. He also proposed that light was a form of electromagnetic radiation.
The Z machine is the largest X-ray generator in the world and is designed to test materials in conditions of extreme temperature and pressure. It is operated by Sandia National Laboratories to gather data to aid in computer modeling of nuclear weapons. The Z machine is located at Sandia's main site in Albuquerque, New Mexico. The electromagnetic pulse when the machine is discharged causes impressive lightning, referred to as "arcs and sparks" or "flashover", which can be seen around many of the metallic objects in the room.
- ...that flash memory devices are able to store data because of tiny transistors that have the ability to control electric current and store electric charge?
- ...that good capacitors, when charged, may retain the charge for several years?
- ...that an explosively pumped flux compression generator can be used to create an electromagnetic pulse that can damage unprotected electrical equipment?
- ...that, according to international standards, high voltage is defined as voltages higher than 1000 V for AC and 1500 V for DC?
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In casual usage, the term electricity is applied to several related concepts that are better identified by more precise terms:
- Electric charge - a fundamental conserved property of some subatomic particles, which determines their electromagnetic interactions.
- Electric field - an effect produced by an electric charge.
- Electric potential - the potential energy per unit of charge associated with a static (time-invariant) electric field.
- Electric current - the flow of electric charge.
- Electrical energy - a form of energy present in any electric field or magnetic field, or in any volume containing electromagnetic radiation.
- Electric power - the amount of work done by an electric current in a unit time.
