Electricity and Magnetism

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# Electricity and Magnetism - PowerPoint PPT Presentation

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

Early Work on Static Electricity
• Leyden Jar
• Static Generator
Charles-Augustin de Coulomb

Coulomb’ Law

1736-1806, France

Luigi Aloisio Galvani

Animal electricity

1737-1771 present-day Italy

Alessandro Giuseppe Antonio Anastasio Volta
• Volta

1745-1827, present-day Italy

André-Marie Ampère
• Electromagnetic molecule
• Showed that the direction of current determines attraction of parallel wires

1775-1836, France

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

Ohm’s Law

I = current (Amps)

V= difference in potential (Volts)

R= resistance (Ohms)

Georg Simon Ohm

1789-1854, present-day Germany

Hans Christian Ørsted
• 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
Early Electric Motor

In answer to William Gladstone as to the practical value of electricity, Faraday replied: One day sir, you may tax it.

Electromagnetic Fields
• Field eliminates problem of action-at-a-distance
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
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).
Magnetic Resonance Imaging
• Also called:
• Nuclear magnetic resonance imaging
• Magnetic resonance tomography
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