Resultado da Busca
18 de nov. de 2020 · Since the dotcom bubble burst back in 2000, technology has radically transformed our societies and our daily lives. From smartphones to social media and healthcare, here's a brief history of the 21st century's technological revolution. Just over 20 years ago, the dotcom bubble burst, causing the stocks of many tech firms to tumble.
- Overview
- The vacuum tube era
electronics, branch of physics and electrical engineering that deals with the emission, behaviour, and effects of electrons and with electronic devices.
Electronics encompasses an exceptionally broad range of technology. The term originally was applied to the study of electron behaviour and movement, particularly as observed in the first electron tubes. It came to be used in its broader sense with advances in knowledge about the fundamental nature of electrons and about the way in which the motion of these particles could be utilized. Today many scientific and technical disciplines deal with different aspects of electronics. Research in these fields has led to the development of such key devices as transistors, integrated circuits, lasers, and optical fibres. These in turn have made it possible to manufacture a wide array of electronic consumer, industrial, and military products. Indeed, it can be said that the world is in the midst of an electronic revolution at least as significant as the industrial revolution of the 19th century.
Theoretical and experimental studies of electricity during the 18th and 19th centuries led to the development of the first electrical machines and the beginning of the widespread use of electricity. The history of electronics began to evolve separately from that of electricity late in the 19th century with the identification of the electron by the English physicist Sir Joseph John Thomson and the measurement of its electric charge by the American physicist Robert A. Millikan in 1909.
Britannica Quiz
Electronics & Gadgets Quiz
At the time of Thomson’s work, the American inventor Thomas A. Edison had observed a bluish glow in some of his early lightbulbs under certain conditions and found that a current would flow from one electrode in the lamp to another if the second one (anode) were made positively charged with respect to the first (cathode). Work by Thomson and his students and by the English engineer John Ambrose Fleming revealed that this so-called Edison effect was the result of the emission of electrons from the cathode, the hot filament in the lamp. The motion of the electrons to the anode, a metal plate, constituted an electric current that would not exist if the anode were negatively charged.
This discovery provided impetus for the development of electron tubes, including an improved X-ray tube by the American engineer William D. Coolidge and Fleming’s thermionic valve (a two-electrode vacuum tube) for use in radio receivers. The detection of a radio signal, which is a very high-frequency alternating current (AC), requires that the signal be rectified; i.e., the alternating current must be converted into a direct current (DC) by a device that conducts only when the signal has one polarity but not when it has the other—precisely what Fleming’s valve (patented in 1904) did. Previously, radio signals were detected by various empirically developed devices such as the “cat whisker” detector, which was composed of a fine wire (the whisker) in delicate contact with the surface of a natural crystal of lead sulfide (galena) or some other semiconductor material. These devices were undependable, lacked sufficient sensitivity, and required constant adjustment of the whisker-to-crystal contact to produce the desired result. Yet these were the forerunners of today’s solid-state devices. The fact that crystal rectifiers worked at all encouraged scientists to continue studying them and gradually to obtain the fundamental understanding of the electrical properties of semiconducting materials necessary to permit the invention of the transistor.
Exclusive academic rate for students! Save 67% on Britannica Premium.
24 de dez. de 2005 · News. The 50 Greatest Gadgets of the Past 50 Years. By Dan Tynan, special to PC World and and PC World Staff. Dec 24, 2005 1:00 am PST. We’re living in the golden age of the gadget. Don’t believe...
1 de dez. de 2022 · Here is Brief History of Electronics from 1745-2021, Greatest Engineers, Scientists, Physicists and Inventors along with details of their Contribution to Electronics and Importance of their Discoveries, Inventions and Works in Field of Electronics. 1745 – Discovery of the Layden Jar.
Brief History of Electronics Timeline ; Date Invention/Discovery Inventor(s) 1900: Old quantum theory: Planck 1905: Theory of relativity: Einstein 1918: Atomic transmutation: Rutherford 1932: Neutron: Chadwick 1932: Particle accelerator: Cockcroft and Walton 1935: Scanning electron microscope: Knoll 1937: Xerography: Carlson 1937 ...
9 de jan. de 2020 · 3D printing, E-cigarettes among the most important inventions of the 21st century. Angelo Young and Michael B. Sauter. 24/7 Wall Street. 0:03. 0:51. The human race has always innovated, and...
The history of electronics is a story of the twentieth century and three key components—the vacuum tube, the transistor, and the integrated circuit. In 1883, Thomas Alva Edison discovered that electrons will flow from one metal conductor to another through a vacuum.
