Electro-technology Rob Iliffe Humphry Davy and the Royal Institution • The Royal Institution was founded in 1799 to promote scientific discoveries and their agricultural and industrial applications. • This was at a time of crisis for Britain, as the French Empire (soon led by Napoleon) tried to blockade food imports. • Humphry Davy (1778-1829) was inspired to pursue a career in chemistry by Lavoisier’s Elements of Chemistry, learning his trade at the ‘Pneumatic Institute’ in Bristol (where he met Watt, Erasmus Darwin and others). • He was appointed 1801 as director of the RI Chemical Laboratory. • Here he did a number of experiments with practical ends, including different kinds of electrical lighting. The Chemical Elements • Davy used the powerful Royal Institution Voltaic pile to make a remarkable number of discoveries of new elements – • decomposing potash in 1807 to produce ‘potassium’, and decomposing soda in the same year to produce ‘sodium’. • Davy used same process to chemically isolate (and name) magnesium, calcium, strontium, barium (all in 1808) and also boron (1809). • His isolation of chlorine (in 1810) was significant, as he showed that the acid of chlorine contained no Oxygen, thus overturning Lavoisier’s definition of acids as compounds of Oxygen. Davy demonstrates new electric light to audience at RI in 1809 (with power drawn from batteries in RI’s basement). Hans Christian Øersted (1777-1851) • Øersted apprenticed at age 13 to his father, who was a pharmacist. • Attended University of Copenhagen in 1794, gaining PhD in physics, philosophy and pharmacy • After this he went on Grand Tour, meeting many major scientists • Appointed as physics lecturer at Copenhagen in 1806, specializing in electrical theory and effects. • 21 April 1820 he noticed that when he turned on a current by connecting both ends of a battery, a nearby compass needle was deflected away very slightly from magnetic North. • Reversing current made needle move in opposite direction Oersted and ‘Naturphilosophie’ • Some have viewed his discovery as a classical example of good luck, • in that he was in a sense ‘prepared’ to discover such effect, believing that electricity and magnetism were variant expressions of an underlying force in nature. • However, Oersted attributed his discovery to his belief in the doctrines of ‘Naturphilosophie’, initially propounded by Immanuel Kant’s disciple Friedrich Schelling: • This was a nebulous grouping of ideas according to which phenomena were reduced to a balance between ‘attractive’ and ‘repulsive’ forces, • all of which were convertible into each other in varied circumstances. Michael Faraday (1791-1867) • Son of blacksmith and member of Sandemanian religious group. • Apprenticed as a bookbinder, he read the books he bound after work, inc. the Encyclopedia Britannica and Jane Marcet’s best-selling Conversations on Chemistry of 1806. • Faraday attended lectures on natural philosophy in London and in due course was invited to hear Davy lecture at the RI. • He took detailed notes on Davy’s lectures, and annotated them, sending them to Davy as a tribute. • By now he was already performing chemical experiments in the bookshop, building his own battery from cheap materials and reproducing Davy’s electrolytic experiments. Faraday at the Royal Institution • Faraday’s apprenticeship ended in 1812 but he gained some employment at the RI (where he would remain for over half a century) when Davy was seriously injured in an explosion • Soon afterwards he was hired as Davy’s assistant, travelling with him during Davy’s extraordinary war-time tour of Europe in 1813. • In 1821 Faraday showed that Oersted’s experiment could be reversed, i.e. that a current-carrying wire could be made to rotate around a magnet, thus producing first electric motor. • By 1830 he was director of the RI, and a brilliant lecturer and disseminator of science to the London elites. Faraday and Electromagnetic Induction • In a major series of demonstrations shown to the public in November 1831, Faraday showed that magnets could be used to create electricity – • a bar magnet that was inserted into a wire coil produced current, and did so again when it was removed. • Following this, he demonstrated that when a current passed through a coil wrapped around a soft iron ring, a current was recorded on another unconnected wire wrapped around the same ring whenever the current was switched on or off. • He termed this electromagnetic ‘induction’ Battery on right provides current flowing through small coil (A), creating magnetic field. When small coil is moved in or out of large coil (B), magnetic flux through large coil changes, inducing a current detected by galvanometer (G) Electro-technology • Electro-magnet, a device where a magnetic field was produced by an electric current, was invented in 1825 by William Sturgeon, a lecturer and instrument-maker. • Sturgeon wound a coil of copper around an iron horseshoe intending (as he saw it) to make the electric fluid visible. • Others increased its power dramatically – e.g. in the early 1830s Joseph Henry in US found that packing a coil extremely tightly enabled his instrument to support a weight of 1600 lbs (726 kilos). • Henry’s work on activating EM power over long distances formed basis of electric telegraph The Electric telegraph • Most important practical application of this electrical research in 1840s and 1850s was development of the electric telegraph, • by the inventor William Fothergill Cooke and the academic Charles Wheatstone in the UK, • and by Joseph Henry, Samuel Morse and Alfred Vail in the US. • For his power source Wheatstone was indebted to work of Henry but for understanding resistance he also owed much to work of Georg Simon Ohm, which he could read in the original German. • Cooke-Wheatstone work was essential for long-distance UK rail services. Cooke-Wheatstone needle telegraph, the first in commercial service (1838).. The code for individual letters on the ‘five needle’ scheme is on Left, Diagram of Receiver showing needles pointing to letter ‘G’ is on Right. Map of existing and projected English railway system, 1845 The New World • Key development was by Samuel Morse, who realised early on that: • “If the presence of electricity can be made visible in any part of the circuit, I see no reason why intelligence may not be transmitted instantaneously by electricity”. • Telegraph, allied to a system of communication (Morse Code), made possible the extension of the US railroad over vast distances. • First message was sent 1844, opening up the West and forging links to the US South-West following the Mexican-American war of 1846-48. • Combination of railways and telegraphic technology changed perceptions of space and time, • Both permitting and requiring the standardization of time zones within and between different countries. The Transatlantic Cable • In the late 1850s, the Glasgow-based physicist William Thomson (later Lord Kelvin) was hired to perform pioneering work on the physics behind the functioning of long-distance telegraph wires. • Facilitating the extraordinary technical feat of laying down the Transatlantic Cable in 1858, though this failed after three weeks (though the standard units of the ohm, volt, watt and ampere were agreed as a result). • Thanks to Thomson’s work on the retardation of underwater signals, a third effort in 1866 to link Ireland to Newfoundland (Canada) succeeded, • reducing communication time between Britain and the US to part of a day, • and stimulating progress in oceanography, steamship design, and many other areas of physics. Systems of Power • Electrical systems and the light technologies they facilitated were crucial for the development of modernity, • Allowing the development of both domestic and street lighting at the end of the Nineteenth Century. • Pioneers of electric systems such as Edison and George Westinghouse competed against each other to provide US cities with infrastructures based on their own configurations, • Electric and gas companies competed with each other to convince consumers that they had the best products, were easiest to use, and were the least dangerous (in the era of the first electric chairs) Nikola Tesla (1856-1943) A great engineer-showman-entrepreneur who worked for The Edison Co. in 1880s but broke away to create his own futuristic visions. He patented a number of different electrical and mechanical devices, working with Westinghouse to pioneer Alternating Current (AC) power systems, but he attracted most attention with his designs for wireless lighting and even wireless communication – ideas that would be taken up and realized by a new generation of inventors such as Guglielmo Marconi (1874- 1937). James Clerk Maxwell (1831-79) • Maxwell the great synthesizer of different elements of electrical theory, and is considered the greatest physicist apart from Newton and Einstein. • Worked on Faraday’s lines of force in early 1850s, attempting to offer a mathematical formulation – resulting in his major paper ‘On Physical Lines of Force’ in 1861. • At Kings College London he calculated the speed of EM propagation showing that it was very close to the speed of light – • And that therefore light and electromagnetism were both transverse undulations in a medium he and others termed ‘ether’. Maxwell’s Treatise on Electricity and Magnetism (1873) • This work effectively mathematized the work of Faraday and others, resulting in his famous 4 partial differential equations (though this was later accomplished by Oliver Heaviside). • Maxwell introduced notion of electromagnetic field as a replacement for Faraday’s lines of force – he understood it as a field emitted by particles but propagated through the ‘luminiferous’ ether. • However, the inability to detect the ether, esp. of the Earth’s movement through it, created a number of problems for late C19 physics. Faraday on Force • Faraday was always suspicious of use of mathematics in relation to electromagnetic researches (in part because he lacked the mathematical training to deal with what he discovered) • this view was in contrast with French (esp.