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Electricity and Magnetism

Electricity and Magnetism. Lightning is a Static Electricity. Early Work on Static E lectricity. Leyden Jar Static Generator. Charles- Augustin de Coulomb. Coulomb’ Law. 1736-1806, France. Luigi Aloisio Galvani. Animal electricity. 1737-1771 present-day Italy.

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Electricity and Magnetism

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  1. Electricity and Magnetism

  2. Lightning is a Static Electricity

  3. Early Work on Static Electricity • Leyden Jar • Static Generator

  4. Charles-Augustin de Coulomb Coulomb’ Law 1736-1806, France

  5. Luigi Aloisio Galvani Animal electricity 1737-1771 present-day Italy

  6. Alessandro Giuseppe Antonio Anastasio Volta • Volta 1745-1827, present-day Italy

  7. André-Marie Ampère • Electromagnetic molecule • Showed that the direction of current determines attraction of parallel wires 1775-1836, France

  8. Electrical Power SI unit of power is Watt W = V * I W = I2 * R W = V2/R W = Watts V = Volts I = Amps R = Ohms

  9. Ohm’s Law I = current (Amps) V= difference in potential (Volts) R= resistance (Ohms) Georg Simon Ohm 1789-1854, present-day Germany

  10. Hans Christian Ørsted • Electric current creates a magnetic field 1777-1851, Denmark

  11. Michael Faraday • Assistant to Humphrey Davy • Chemistry • Electricity and magnetism 1791-1867, Britain

  12. Faraday Induction Experiment • induction coil (A&B) • Galvanometer

  13. Early Electric Motor Faraday’s electromagnetic rotation experiment (1821) In answer to William Gladstone as to the practical value of electricity, Faraday replied: One day sir, you may tax it.

  14. Faraday Electromagnetic Field Experiment

  15. Electromagnetic Fields • Field eliminates problem of action-at-a-distance

  16. AC and DC Current

  17. Circuits in Parallel and Series Series Parallel

  18. The War of the Currents in 1880’s George Westinghouse Thomas A. Edison Promoted DC current Could be used to charge batteries directly Early systems could be used in parallel or series Low efficiency in long distance transmission Edison’s disinformation campaign • Promoted AC current • Difficult to charge batteries without transformer • Early systems could be used only in series • Early AC motors not practical • More efficient transmission over long distances

  19. Willamette Falls and Niagara Falls • Willamette Falls transmission first long-distance transmission (DC). Knocked out by flood and a quick AC replacement was used (1890). • Niagara Falls station, international long-distance transmission. Awarded to Westinghouse (1893).

  20. Electric Motors

  21. Magnetic Resonance Imaging • Also called: • Nuclear magnetic resonance imaging • Magnetic resonance tomography

  22. James Clerk Maxwell • Physicist who worked on thermodynamics, optics, and electromagnetism • Unification of optics, electricity, and magnetism by Maxwell's equations • Gauss’s Law for electricity (single electrical charges exist, also Coulomb’s Law) • Gauss’s Law for magnetism (magnetic monopoles do not exist) • Faraday’s Law of induction (a varying magnetic field induces an electrical field) • Ampere’s Law (a varying electrical current –or fields- can create a magnetic field) 1831-1879, Britain

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