GEOS 24705 / ENST 24705 / ENSC 21100 2018 Lecture 10 Electricity Electricity not only transports kine@c energy It also allows Doing work more flexibly: engine anD motor characteris@cs 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 unDeres@mate 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 excep0ons) 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 Electrosta0c 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 Electrosta0c 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, BaFeryfacts.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? Intersec@on of electricity anD magne@sm 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 baFeries) 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 .