Chaos, Communication and Consciousness Module PH19510 Lecture 4 The Dawn of the Electric Age.
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Transcript of Chaos, Communication and Consciousness Module PH19510 Lecture 4 The Dawn of the Electric Age.
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Chaos, Communication and ConsciousnessModule PH19510
Lecture 4
The Dawn of the Electric Age
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Review of Lecture #2
Pre-electronic Communication Pictographs Development of the alphabet Number systems Printing
Transfer of Information Navigation Signalling
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CommunicationThe dawn of the electric age The Electric Pioneers First messages by wire Development of telegraphy Samuel Morse and his code
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Highly RecommendedElectric Universe David Bodanis £7.99 ISBN
0-349-11766-7
Aventis prize for popular science
How Electrons hold the universe together
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Electricity in antiquity
Lightning Ancient Greece Thales (600BC) Rubbed Amber with
fur picked up feathers
Static electricity “Resinous” vs
“Vitreous”
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Benjamin Franklin (1706-1790)
Printer, scientist, writer, inventor, activist, statesman
Static electricity +ve and –ve charge 1752 Proved storm
clouds are charged
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Luigi Galvani (1737-1798)
1780 Frogs leg Dissimilar
metals Static Bioelectricity
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Alessandro Volta (1745-1827)
Lombary, Italy 1800
Voltaic pile Battery
Zinc/Silver Brine/Cardboard Steady current
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The Zinc/Silver Cell
Zinc Anode Silver Cathode Zn(s) Zn2+(aq) + 2e-
2H+(aq)+2e- H2 (g)
≈0.75 volts/element
Ag
Zn
+ve
-ve
Cardboard + Brine
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1820 – A key year
Link between Electricity & Magnetism HC Ørsted (Denmark) Compass needle
Galvanometer J Schweigger Wind wire around compass Increased sensitivity
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Andrè-Marie Ampere (1775-1836)
1820 Formalised EM Theory
1821 Proposed Telegraphy with galvanometers
1 wire per galvanometer
200 ft (60-70m)
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Early systems based on galvanometers Schilling 1832 Gauss & Weber 1833 Wheatstone & Cooke
5 Needle Telegraph 1837
Commercial system 1839
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William Sturgeon invents the Electromagnet 1825 b. 1783 1825 Electromagnet
Coil of wire on iron Uninsulated wire
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Joseph Henry (1797-1878) – Electrical signalling at a distance 1827 Improves
electromagnet Many turns of insulated wire
1830 First signalling Ring bell >1 mile of cable
1837 Electromechanical Relay
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The electromechanical relay
Switch held open by spring
Electromagnet Current flows in
electromagnet magnetic field switch actuated Current flows in
switched circuit
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Samuel Morse & Alfred Vail
1838 – First system test Vail developed signalling code 1843 – U.S. congress funds $30,000 for line from
Washington to Baltimore – 40 miles (65km) 1844 Line operational
“What hath God wrought”
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Morse’s apparatus
Paper tape moved by clockwork
Electromagnet pulls ‘pendulum’
Marks embossed on paper tape
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Paper Tape Output
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Morse Code
Evolved from Vail’s original
Letters & Numbers Punctuation 2 symbols
Dot Dash
Variable length Frequent letters, shortest
codes
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Review of Lecture #3
Dawn of the electric age Key technologies
Cells & Batteries Electromagnet Relay
Use of standardised code