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Electricity and Magnetism

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Electricity and Magnetism

- Leyden Jar
- Static Generator

Coulomb’ Law

1736-1806, France

Animal electricity

1737-1771 present-day Italy

- Volta

1745-1827, present-day Italy

- Electromagnetic molecule
- Showed that the direction of current determines attraction of parallel wires

1775-1836, France

SI unit of power is Watt

W = V * I

W = I2 * R

W = V2/R

W = Watts

V = Volts

I = Amps

R = Ohms

I = current (Amps)

V= difference in potential (Volts)

R= resistance (Ohms)

Georg Simon Ohm

1789-1854, present-day Germany

- Electric current creates a magnetic field

1777-1851, Denmark

- Assistant to Humphrey Davy
- Chemistry
- Electricity and magnetism

1791-1867, Britain

- induction coil (A&B)
- Galvanometer

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.

- Field eliminates problem of action-at-a-distance

Series

Parallel

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

- 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).

- Also called:
- Nuclear magnetic resonance imaging
- Magnetic resonance tomography

- 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