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