Lecture+10+feb7 - Lecture 10 Current and Resistance “Mr....

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Unformatted text preview: Lecture 10 Current and Resistance “Mr. Watson—come here—I want to see you” What are these 2 items and how are they related? S. Morse in 1844 Al Bell in 1876 A little history • early 1800’s—crude telegraphs • 1837—first commercial telegraph for railroad use • 1844—Samuel Morse public demo of telegraph • 1866---Trans-atlantic telegraph cable • 1876---Alexander G. Bell’s new telephone • 1879---Thomas Edison caps 50 years of light bulb research • 1882—Edison’s first electric power generating plant • 1880’s—Industry embraces electric lighting and motors • 1889-92—Edison-General Electric becomes G.E. • 1899—Trans-atlantic wireless signal Electric Current, I I = dQ/dt in Coulombs/s = Ampere (A) (direction convention is that of + charge flow) The actual flow direction of particles may be different from I: • Semiconductors (electrons or + holes) • Metals (electrons) • Ionic solutions (+ or – ions, or both) • Salt water solution of Na and Cl DEMO Resistance, R...
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This note was uploaded on 02/15/2012 for the course PHYS 240 taught by Professor Winn during the Winter '11 term at University of Michigan.

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Lecture+10+feb7 - Lecture 10 Current and Resistance “Mr....

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