By Herbert W. Meyer
Written in order to be understood by way of the non-technical reader who's fascinated with the starting place of all of the electric and electromagnetic units that encompass him, this heritage additionally offers a handy compendium of data for these accustomed to and magnetic fields. The booklet strikes alongside at a speedy velocity, because it needs to whether it is to hide the big proliferation of advancements that experience happened over the past hundred years or so. the writer has struck a attainable stability among the human part of his tale, introducing these biographical info that aid boost it, and its technical aspect, explaining theories and "how issues paintings" the place this turns out applicable. He additionally achieves a stability in recounting the invention of uncomplicated medical rules and their technological applications—the myriad of units and innovations that make the most of power and knowledge in electromagnetic shape. certainly, one of many very important topics of the booklet is the shut and reciprocal courting among technological know-how and expertise, among idea and perform. earlier than nearly 1840, the simply medical investigations of electric and magnetic phenomena have been mostly advert hoc and observational, and primarily no expertise according to them existed. Afterwards, the clinical explorations turned extra programmatic and mathematical, and technical functions and innovations started to be produced in nice abundance. In go back, this know-how paid its debt to natural technological know-how by means of offering it with a chain of measuring tools and different study units that allowed it to improve in parallel. even if this publication stories the early discoveries, from the magnetic lodestone and electrostatic amber of antiquity to Galvani's frog's legs and Franklin's kite-and-key of the 1700s, its significant emphasis is at the post-1840 advancements, because the following bankruptcy titles will verify: Early Discoveries—Electrical Machines and Experiments with Static Electricity—Voltaic electrical energy, Electrochemistry, Electromagnetism, Galvanometers, Ampere, Biot and Savart, Ohm—Faraday and Henry—Direct present Dynamos and Motors—Improvements in Batteries, Electrostatic Machines, and different Older Devices—Electrical tools, legislation, and Definitions of Units—The electrical Telegraph—The Atlantic Cable—The Telephone—Electric Lighting—Alternating Currents—Electric Traction—Electromagnetic Waves, Radio, Facsimile, and Television—Microwaves, Radar, Radio Relay, Coaxial Cable, Computers—Plasmas, Masers, Lasers, gasoline Cells, Piezoelectric Crystals, Transistors—X-Rays, Radioactivity, Photoelectric impact, constitution of the Atom, Spectra.
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Extra resources for A History of Electricity and Magnetism
It consisted of a metallic rod with a number of fine points, SO mounted that the points were close to the revolving electrified surface. THE LEYDEN JAR A very important discovery was made on November 4, 1745 by E. G. von Kleist of Kammin, Pomerania, Germany, which was first credited to Professor Pieter van Musschenbroek and his assistant Cunaeus of Leyden, Holland, but priority belongs to von Kleist. Nevertheless, the invention has since been known as the Leyden jar. It was found that a bottle partly filled with water and containing a metal rod which projected through the neck would, when held in the hand and the rod presented to an electrical machine, receive a powerful charge.
In another series of experiments, Franklin became interested in the nature of the electric field surrounding a charged body. In order to visualize the shape of the field, he suspended electrified bodies in still air, and then filled the air with smoke from rosin, which he had dropped on hot plates. The smoke, much to his amazement and gratification, formed beautiful patterns about the charged body. Franklin had a friend at Boston, a Mr. Kinnersley, who was also interested in electricity. They corresponded frequently concerning their experiments.
It is now known that the charge is of the nature of a strain in the dielectric. In 1748, Franklin descrihed an electrostatic jack, or motor. HC attached two metal knobs to diametrically opposite sides of an insulating wheel and placed tbe wheel SO that it would rotate between two stationary insulated knobs, with a vcry small clearance between the rotatiog and stationary oncs. When the stationary knohs wcre electrified, onc positively and the otber ncgatively, the wheel was caused t o rotate. The knobs on the wheel were fiat attracted, and as t h e y a p p r o a c h e d t b e stationary k n o h s a spark passed, making the charge on both of the samc sign.