1. Chaos, Communication and Consciousness Module PH19510 Lecture 4 The Dawn of the Electric Age

2. Review of Lecture #2 Pre-electronic Communication  Pictographs  Development of the alphabet  Number systems  Printing Transfer of Information  Navigation  Signalling

3. Communication The dawn of the electric age The Electric Pioneers First messages by wire Development of telegraphy Samuel Morse and his code

4. Highly Recommended Electric Universe David Bodanis £7.99 ISBN  0-349-11766-7 Aventis prize for popular science How Electrons hold the universe together

5. Electricity in antiquity Lightning Ancient Greece Thales (600BC) Rubbed Amber with fur  picked up feathers Static electricity “Resinous” vs “Vitreous”

6. Benjamin Franklin (1706-1790) Printer, scientist, writer, inventor, activist, statesman Static electricity +ve and –ve charge 1752 Proved storm clouds are charged

7. Luigi Galvani (1737-1798) 1780 Frogs leg Dissimilar metals Static Bioelectricity

8. Alessandro Volta (1745-1827) Lombary, Italy 1800  Voltaic pile  Battery Zinc/Silver Brine/Cardboard Steady current

9. The Zinc/Silver Cell Zinc Anode Silver Cathode Zn(s)  Zn 2+ (aq) + 2e - 2H + (aq)+2e -  H 2 (g) ≈0.75 volts/element Ag Zn +ve -ve Cardboard + Brine

10. 1820 – A key year Link between Electricity & Magnetism  HC Ørsted (Denmark)  Compass needle Galvanometer  J Schweigger  Wind wire around compass  Increased sensitivity

11. Andrè-Marie Ampere (1775-1836) 1820 Formalised EM Theory 1821 Proposed Telegraphy with galvanometers 1 wire per galvanometer 200 ft (60-70m)

12. Early systems based on galvanometers Schilling 1832 Gauss & Weber 1833 Wheatstone & Cooke  5 Needle Telegraph 1837  Commercial system 1839

13. William Sturgeon invents the Electromagnet 1825 b. 1783 1825 Electromagnet  Coil of wire on iron  Uninsulated wire

14. 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

15. The electromechanical relay Switch held open by spring Electromagnet Current flows in electromagnet  magnetic field  switch actuated Current flows in switched circuit

16. 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”

17. Morse’s apparatus Paper tape moved by clockwork Electromagnet pulls ‘pendulum’ Marks embossed on paper tape

18. Paper Tape Output

19. Morse Code Evolved from Vail’s original Letters & Numbers Punctuation 2 symbols  Dot  Dash Variable length  Frequent letters, shortest codes

20. Review of Lecture #3 Dawn of the electric age Key technologies  Cells & Batteries  Electromagnet  Relay Use of standardised code