THE DEVELOPMENT OF ELECTRICITY
The phenomenon which Thales had observed and recorded five centuries before the birth of Christ aroused the interest of many scientists through the ages.They made various practical experiments in their efforts to identify the elusive force which Thales had likened to a 'soul' and which we now know to have been static electricity.
Of all forms of energy, electricity is the most baffling and difficult to describe.An electric current cannot be seen.In fact it does not exist outside the wires and other conductors which carry it.A live wire carrying a current looks exactly the same and weighs exactly the same as it does when it is not carrying a current.An electric current is simply a movement or flow of electrons.
Benjamin Franklin, the American statesman and scientist born in Boston in 1706, investigated the nature of thunder and lightning by flying a child's kite during a thunderstorm.He had attached a metal spike to the kite, and at the other end of the string to which the kite was tied he secured a key.As the rain soaked into the string, electricity flowed freely down the string and Franklin was able to draw large sparks from the key.Of course this could have been very dangerous, but he had foreseen it and had supported the string through an insulator.He observed that this electricity had the same properties as the static electricity produced by friction.
But long before Franklin many other scientists had carried out research into the nature of electricity.
In England William Gilbert (1544-1603) had noticed that the powers of attraction and repulsion of two non-metallic rods which he had rubbed briskly were similar to those of lodestone and amber - they had acquired the curious quality we call magnetism.Remembering Thales of old he coined the word 'electricity'.
Otto von Guericke (1602-1686) a Mayor of Magdeburg in Germany, was an amateur scientist who had constructed all manner of gadgets.One of them was a machine consisting of two glass discs revolving in opposite directions which produced high voltage charges through friction.Ramsdenand Wimshurst built improved versions of the machine.
A significant breakthrough occurred when Alessandro Volta (1745- 1827) in Italy constructed a simple electric cell (in 1799) which produced a flow of electrons by chemical means.Two plates, one of copper and the other of zinc, were placed in an acid solution and a current flowed through an external wire connecting the two plates.Later he connected cells in series (voltaic pile) which consisted of alternate layers of zinc and copper discs separated by flannel discs soaked in brine or acid which produced a higher electric pressure (voltage).But Volta never found the right explanation of why his cell was working.He thought the flow of electric current was due to the contact between the two metals, whereas in fact it results from the chemical action of the electrolyte on the zinc plate.However, his discovery proved to be of incalculable value in research, as it enabled scientists to carry out experiments which led to the discoveries of the heating, lighting, chemical and magnetic effects of electricity.
One of the many scientists and physicists who took advantage of the 'current electricity' made possible by Volta's cells was Hans Christian Oersted (1777-1851) of Denmark.Like many others he was looking for a connection between the age-old study of magnetism and electricity, but now he was able to pass electric currents through wires and place magnets in various positions near the wires.His epoch-making discovery which established for the first time the relationship between magnetism and electricity was in fact an accident.
While lecturing to students he showed them that the current flowing in a wire held over a magnetic compass needle and at right angles to it (that is east-west) had no effect on the needle.Oersted suggested to his assistant that he might try holding the wire parallel to the length of the needle (north-south) and hey presto, the needle was deflected! He had stumbled upon the electromagnetic effect in the first recorded instance of a wire behaving like a magnet when a current is passed through it.
A development of Oersted's demonstration with the compass needle was used to construct the world's first system of signaling by the use of electricity.
In 1837 Charles Wheatstone and William Cooke took out a patent forthe world's first Five-needle Telegraph, which was installed between Paddington railway station in west London and West Drayton station a few miles away.The five copper wires required for this system were embedded in blocks of wood.
Electrolysis, the chemical decomposition of a substance into its constituent elements by the action of an electric current, was discovered by the English chemists Carlisle and William Nicholson (1753-1815).If an electric current is passed through water it is broken down into the two elements of which it is composed -- hydrogen and oxygen.The process is used extensively in modern industry for electroplating.Michael Faraday (1791-1867) who was employed as a chemist at the Royal Institution, was responsible for introducing many of the technical terms connected with electrolysis, like electrolyte for the liquid through which the electric current is passed, and anode and cathode for the positive and negative electrodes respectively.He also established the laws of the process itself.But most people remember his name in connection with his practical demonstration of electromagnetic induction.
In France Andre-Marie Ampere (1775-1836) carried out a complete mathematical study of the laws which govern the interaction between wires carrying electric currents.
