GEOS 24705 / ENST 24705 / ENSC 21100 2018 Lecture 10

Electricity

Electricity not only transports kinec energy It also allows doing work more flexibly: engine and motor characteriscs can differ

Kinec ------(generator)------> Electrical ------(motor)------> Kinec 1/3 of total primary energy now goes to make electricity

61% through heat engine total e ~ 32% transportaon e ~ 21% turbines e ~ 23% ? (likely underesmate of thermal efficiency) All current use of steam: turbines spin generators to make electricity

Steam turbines are choice for external combuson

All reciprocang engines are now internal combuson

(with some minor excepons)

History of electricity technology Stac electricity discovered in ancient mes Word origin: “electricity” from New Lan “electricus”, constructed (1600, Gilbert, De Magnete) from Lan electrum, “amber”, from Gr. “ilektron”

Thaleus of Miletus describes 585 BC that amber rubbed with fur could aract other objects

Kinec energy à electrical energy: separate charge Image from: Wikimedia commons Stac electricity discovered in ancient mes Word origin: “electricity” from New Lan “electricus”, constructed from Lan electrum, “amber”, Gilbert De Magnete, 1600

1660, von Guericke, electrostac “generator” 1730s: Hauksbee shows that rubbing amber in a chamber containing mercury vapor causes light emission

Kinec energy à electrical energy: separate charge Images from: “The History of Electrostac Generators” Stac electricity discovered in ancient mes Word origin: “electricity” from New Lan “electricus”, constructed from Lan electrum, “amber”, Gilbert De Magnete, 1600

1795s: experiments with electrostac 1750s, demonstraon of stac electricity capacitors (store charge on metal) discharge: “electric kiss”

Kinec energy à electrical energy: separate charge Images from: “The History of Electrostac Generators” Chemical reacons can create electric currents Allessandro Volta – demonstrated 1791, “Voltaic pile” 1800

Voltaic pile was stack of different metals (Zn, Cu) soaked in brine (inspired by Galvani’s accidental finding).

Chemical energy à electrical energy: metal oxidizes Images from: Wikipedia, Baeryfacts.co.uk Electricity enters the popular imaginaon Allessandro Volta – demonstrated 1791, “Voltaic pile” 1800

Luigi Galvani frog experiment, 1792

Mary Shelley, 1818

How do you get useful work from electricity?

Intersecon of electricity and magnesm allows transformaon of electrical energy to / from work

“dynamic electricity” = flow of steady current

Electric currents can create magnetic fields

https://www.youtube.com/ watch?v=V-M07N4a6-Y

Electromagnet, 1824 (Sturgeon) Electricity research started with motors (first powered by baeries)

Rotang electromagnet, Wm. Ritchie, 1833

Rotang electromagnet, Wm. Sturgeon, 1838 Rotang wire in Hg, Faraday, 1830s

Reciprocang engine, Daniel Davis (?) 1840s Revolving armature engine, DC electric fan, Edison 1898 Daniel Davis 1848 Images from: Sparkmuseum