History of Electricity from its Beginning
“What is Electricity”? The Electron Theory predicted by H.A. Lorentz in 1895, could be near the answer and as we know what electricity does and how to harness it, we are satisfied, that this Theory could be the answer. We do know however, that there are three forms of electricity: – Static, Electrochemical and Electromagnetic Induction, therefore as an introduction to electricity, it will be interesting to give a brief description of how these forms were discovered.
Static Electricity top
Dr. William Gilbert’s Theory – 1600
As early as the latter part of the 16th century, scientists and experimenters were exploring the behavior of static electricity. Dr. William Gilbert, the Court Physician to Queen Elizabeth I, realised that a force was created, when a piece of amber (resin) was rubbed with wool and attracted light objects. In describing this property today, we say that the amber is “electrified” or possesses and “electric charge”. These terms are derived from the Greek word “electron” meaning amber and from this, the term “electricity” was developed.
It is possible to impart an electric charge, to any other solid material, by rubbing it with any other dry material. For instance a comb becomes electrically charged when passing through dry hair. This suggests that an electric charge consists of transferring something from one body to another , so that one body has an excess and the other has a deficiency of that something. It was not until the end of the 19th century that this “something” was found to consist of negative electricity, known today as electrons.
Benjamin Franklin’s Theory – 1747
After Gilbert discovery that a force of electric charge is created by friction of different materials, Benjamin Franklin in 1747, improved on this by announcing that this electric charge exists of two types of electric forces, an attractive force and a repulsive force. To identify these two forces, he gave the names, positive and negative charges and to symbolise them, he used the + and – signs the + being for positive and the – for negative.
Volta Electric’s Battery – 1800
While the science of electrostatics or the study of static electricity had been progressing and its fundamental laws were becoming clear and modified, the study of current electricity had begun. Electrochemistry is that branch of science, which deals with the production of electricity by chemical energy as in the electric cells or batteries.
It started in 1791, with the experiments that Luigi Galvani, an anatomy professor , noted that when he fastened the legs of a freshly killed frog to a copper hook and hung the hook over an iron railing, the frog’s legs twitched. Galvani then concluded that the frog’s legs contained electricity and was released when the legs touched metal.
This discovery greatly intrigued another Italian Physicist, Alexandro Volta, who carried out many experiments with metal and chemicals. In 1800, Volta succeeded in producing a simple form of coil and by adding a pile of these cells, it became known as the “Voltaic Pile”. This was the first instrument for producing and to maintain an electric current. He therefore laid the foundations of electrochemistry, with this electric battery. Volta was given the honour by naming the unit of electric potential the volt – after him.
Amperes – Current In a Circuit – 1820 top
In 1820, a physicist Hans Christian Oersted, learned that a current flowing through a wire would move a compass needle placed beside it. This showed that an electric current produced a magnetic field, this was followed up in the same year by the French physicist Andre Marie Ampere, who had shown that two parallel wires, carrying current, attracted each other if the currents flowed in the same direction and vice versa.
He formulated in mathematical terms, the laws that govern the interaction of already currents with magnetic fields in a circuit and as a result of this the unit of electric current – the amp – was derived from his name.
Ohms – Currents Causing Heat – 1826 top
In 1826, the German Physicist Georg Simon Ohm, examined Volta’s Principle of the electric battery and the relationship of currents in a circuit, by Ampere. He noted that when there was a current in a circuit, there was at times, heat, in reference to a different metal. He discovered this relationship between current and heat, there was some “resistance” to the flow of current, in the circuit.
By discovering this, he found out that if the potential difference (volts), remained constant, the current was in proportion to the resistance. This unit of electrical resistance – the ohm – was named after him. He also formulated a law, showing the relationship between volts, amps and resistance and this law was called “Ohm’s Law” also named after him. This law as we know it today, is the basis of electricity.
Basis of Electricity – 1826 top
We know the basis of electricity, as summed up by “Ohm’s Law”, so we can also apply this law in a practical way, referred to as “The Water Analogy of Electricity”.
Electricity can be relate to water as follows:
Volts in a circuit, is pressure and is equivalent to, the pressure of water in a pipe.
Amps in a circuit, is the flow of current in that circuit and is equivalent to, the water flowing through a pipe.
Resistance , is the type and size of the metal allowing that current to flow in a circuit and is equivalent, to the friction in the pipe and the size of the pipe.
Electromagnetic Induction top
Faraday’s Electromagnetic Induction – 1831
As mentioned previously, H.C. Oersted, in 1820, demonstrated that electric currents produce a magnetic field. Faraday noted this and in 1821, he experimented on the theory that, if electric currents in a wire can produce magnetic fields, then magnetic fields should produce electricity. By 1831, he was able to prove this and through his experiment, was able to explain, that these magnetic fields were lines of force. These lines of force would cause a current to flow in a coil of wire, when the coil is rotated between the poles of a magnet. This action then shows that the coils of wire being cut by lines of magnetic force, in some strange way, produces electricity.
These experiments, convincingly demonstrated the discovery of electromagnetic induction in the production of electric current, by a change in magnetic intensity. Michael Faraday founded the science of electromagnetism and his discoveries form the basis of our modern electrical industry today.
Having described the three forms of electricity and also Ohm’s Law, giving us the basis of electricity, it will be interesting to see how these were applied and utilised as time went on.
Primary Cells & Secondary Batteries – 1836 top
One of the first experiments in applying the practical use of the electricity was when Volta discovered the primary cell (electric battery) in 1800.
In one of Faraday’s experiments with magnetic fields in 1821, he devised the principle of the electric motor, but no motor of commercial significance was produced until about 1870, so the only practical method of producing electric currents at this time was by means of primary cells.
The next advance of great importance, was the introduction of the electric carbon arc light, which was exhibited in experimental form in 1808, by Sir Humphry Davey. He used a large battery to provide current for his demonstration, as these arc lights require a heavy current and no means of mechanically generating electricity had as yet been developed.
The principle of these arc lights, is that when two carbon rods in a circuit are brought together, an arc is created. This arc, which gives off a brilliant incadescence, is maintained as long as the rods are just separated and keep mechanically fed this way, to maintain the arc. As the arc lights took a heavy current from these batteries, it was not until about 1860, that practical use was made of them. By this time adequate generating sources were developed and then they were only used mainly for street lighting and in picture theaters.
Although arc lighting was still used until the early 1900’s they were eventually superseded by the incandescent light, except that most picture theaters use them in their projectors even today.
The D.C. Electric Motor – 1860-71 top
The history of the electric motor begins with Hans Christian Oersted, who discovered in 1820, that electricity produced a magnetic field, as mentioned before. Faraday followed up this in 1821, by devising the principle of the electric motor of his own design. Some of those worth mentioning are Jacobi in 1834, Elias in 1842, Froment in 1844 and Pacinotti in 1860. Pacinotti used a ring wound armature which was used in 1860 and was an outstanding advance on any previous attempts. Most of these motors were in the experimental stage but it was not until 1871, that Zenobe Theophile Gramme introduced his motor, which was really a development of Pacinotti’s machine. This motor was said to be the first electric motor of commercial significance.
During this period the scientists concentrated on the “motor”, but meanwhile, experiments with machines producing electricity dynamically were under way
The Telephone – From 1876 top
Since the telegraph was invented by Samual Morse in 1837, great advances had been made in its utilisation, but it continued as a telegraph system using Morse Code for its communication.
Alexander Graham Bell in 1875, was interested in telegraphy and realised that in using Morse Code over telegraph wires there should be other ways to this form of communication using electricity. He was also interested in acoustic and sound and worked on the principle that if Morse Code created electrical impulses in an electrical circuit, some means of sound causing vibration in the air, could also create electrical impulses in a circuit. In an experiment he use a “diaphragm” associated with an electrical circuit and any sound reaching the diaphragm, would cause electrical impulses and these were carried on to the other end of the circuit. These then would cause vibrations to another diaphragm at this end and would be in relation to the first diaphragm, hence the sound was electrically transmitted from one end of the circuit to the other end.
He continued working on these experiments and on March 7th, 1876 his telephone was officially patented and a successful demonstration was made at an Exhibition Hall in Philadelphia. Graham Bell was just in time to patent his telephone, as another inventor Elisha Gray, was experimenting also on a similar invention. Later, Edison improved on the diaphragm – then called transmitters – but Bell won the day, by being given the honour of inventing the “telephone”.
The Incandescent Light – From 1879 top
After Arc Lights were invented and put to practical use by 1860, the inventors began working out something that could replace the arc light, as well as other lighting. Their experiments were based on the principle of using a light that could be used universally, such as in the home or office instead of just for street lighting.
They started to use metal such as platinum for a filament and enclosed it in a glass bulb but it soon burnt out. However, it was not until 1879, that a satisfactory lamp was produced.
Almost simultaneously, Thomas Edison in America and Joseph Swan in England, produced a carbon filament lamp. Edison replaced platinum with a filament of carbonised cotton thread and Swan used a carbon filament, from parchmentised cotton thread also. Edison then patented his invention on the 21st December 1879 and this proclaimed the news of this achievement to the world. With this invention, he became the first to invent a commercially usable incandescent lamp. It was not long before further experiments were made to increase the efficiency of the incandescent lamp. This was done by concentrating on the suitable material for the filament. In 1911, tungsten wire was used. With the filament wire being a success, the next step was in 1913, when the gas filled lamp appeared. By then in 1934, the coiled coil pearl lamp was introduced as we know it today.
The DC Generator – From 1871 top
With the development of the carbon filament lamp by Edison in 1879, the DC generator then became one of the essential components of the constant-potential lighting systems. Previous to this only arc lights were used for street lighting.
Then commercial lighting and residential lighting, as the inventors were aiming at, became practical and so the electric light and power industry was born.
When H. C. Oersted in 1820, discovered that an electric current produces magnetic fields, the DC motor was developed.
At this time, they were satisfied with the DC motor but they did not think that magnetism could produce electricity, such as by the DC generator. This was soon overcome, when Michael Faradey in 1831, discovered the principle of electromagnetic induction. He found that moving a magnet through a coil of wire, caused an electric current to flow in the wire.
The electric motor and the electric generator, are based on this principle but it was not until 1871, when Gramme introduced his motor and generator, that the electric generator was used commercially. By 1872, Siemens and Halske of Berlin improved on Gramme’s generator, by producing the drum armature. Other improvements were made, such as the slotted armature in 1880 but by 1882, Eidson had completed the design of the system we still use to distribute electricity from power stations.
The Alternating Current System – From 1883 top
With the DC generator being in operation by 1882, it was not long before the first direct-current central power station built in the United States, in New York, was in operation in 1882. Around this period however, the scientists were still active, as they realised that with DC current, they could not transmit it over long distances. Nikola Tesla of America, was experimenting on generators and he discovered the rotating magnetic field in 1883, which is the principle of alternating current.
This rotating magnetic field changes in opposite directions fifty time a second and is called 50 Hertz. The alternating current generator has a rotating magnetic field and is referred to as a A.C. current. The direction current generator generates current in the one direction hence DC current. He then developed plans for an induction motor, that would become his first step towards the successful utilisation of alternating current.
In 1885, George Westinghouse, head of the Westinghouse Electric Company, bought the patent rights to Tesla’s polyphase system of alternating current. In America, in 1886 the first alternating current power station was placed in operation, but as no AC motor was available, the output of this station was limited to lighting.
Although Telsa developed the polyphase AC induction motor in 1883, it was not put into operation until 1888 and from then on, this AC motor became the most commonly used motor for supplying large amounts of power.
Having discovered the alternating current systems of generating electricity, we find that apart from Tesla’s discovery of the rotating magnetic field, the alternating current transformer was developed. From Faradays, discovery of electromagnetic induction, this principle was used to create the transformer.
The transformer is a simple device, mainly consisting of two separate coils of wire. When a moving current is applied to the first coil, a current is “induced” into the second coil. By this induction, the magnitude of the voltage in the second coil depends on the number of turns in the coil. If the number of turns in the second coil is greater than the first coil, the voltage is increased and vice versa.
The first transformer was announced by L. Caulard and J. D. Gibbs in 1883 and so this device revolutionised the systems of power transmission. By generating at a low voltage, the transformer steps it up to a high voltage for transmission and then to a lower voltage where required.
Although DC current was still being used during this period of AC current development, it was not long before the advantages of AC current were evident and the AC current system gradually took over.