Men's understanding of electromagnetic phenomena and the gradual establishment of electromagnetic science have gone through a long process. The understanding of electrical phenomena mainly started from lightning, friction electricity and certain creatures with the ability to discharge electricity, while the understanding of magnetic phenomena mainly started from certain minerals with magnetic properties. AOMAG Magnetics would like to take a look at this process with you.
600 BC - Lodestone
The magnetic properties of natural ferric ferrite (Fe3O4) stones (lodestones) were described by Greek philosophers.
600 BC - Electric Charge
Amber is a yellowish, translucent mineral. As early as 600 BC the Greek philosopher, Aristophanes was aware of its peculiar property: when rubbed with a piece of fur, amber develops the ability to attract small pieces of material such as feathers. For centuries this strange, inexplicable property was thought to be unique to amber. This strange effect remained a mystery for over 2000 years, until, around AD 1600, Dr William Gilbert investigated the reactions of amber and magnets and first recorded the word 'Electric' in a report on the theory of magnetism.
Later in, in 1895, H.A. Lorentz developed the Electron Theory. We now know that there are three ways to generate electricity: Static, Electrochemical and Electromagnetic Induction.
1175 - First Reference to a Compass
Alexander Neckem an English monk of St. Albans describes the workings of a compass.
1269 - First Detailed Description of a Compass
Petrus Peregrinus de Marincourt, a French Crusader, describes a floating compass and a compass with a pivot point.
1600 - Static Electricity (De Magnete)
In the 16th century, William Gilbert(1544-1603), the Court Physician to Queen Elizabeth I, proved that many other substances are electric (from the Greek word for amber, elektron) and that they have two electrical effects. When rubbed with fur, amber acquires resinous electricity; glass, however, when rubbed with silk, acquires vitreous electricity. Electricity repels the same kind and attracts the opposite kind of electricity. Scientists thought that the friction actually created the electricity (their word for charge). They did not realize that an equal amount of opposite electricity remained on the fur or silk. Dr. William Gilbert, realized 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 was not until the end of the 19th century that this "something" was found to consist of negative electricity, known today as electrons.
Gilbert also studied magnetism and in 1600 wrote "De magnete" which gave the first rational explanation to the mysterious ability of the compass needle to point north-south: the Earth itself was magnetic. "De Magnete" opened the era of modern physics and astronomy and started a century marked by the great achievements of Galileo, Kepler, Newton and others.
Gilbert recorded three ways to magnetize a steel needle: by touch with a loadstone; by cold drawing in a North-South direction; and by exposure for a long time to the Earth's magnetic field while in a North-South orientation.
1660 - Static Electricity Generator
Otto von Guericke invents a crude machine for producing static electricity.
1729 - Conductors and Nonconductors
Stephen Gray describes that power possessed by one electrified body could be passed to another by connecting them.
1734 - Electrical Attraction and Repulsion
Charles Francois de Cisternay Du Fay first to recognize two kinds of electricity.
1730 - Compound Magnet
Servigton Savery produces the first compound magnet by binding together a number of artificial magnets with a common pole piece at each end.
1740 - First Commercial Magnet
Gowen Knight produces the first artificial magnets for sale to scientific investigators and terrestrial navigators.
1745 - Electric Force, Capacitor
Leyden Jar is one of the earliest and simplest forms of electric capacitor, invented independently about 1745 by the Dutch physicist Pieter van Musschenbroek of the University of Leyden and Ewald Georg von Kleist of Pomerania. The original Leyden jar was a stoppered glass jar containing water, with a wire or nail extending through the stopper into the water. The jar was charged by holding it in one hand and bringing the exposed end of the wire into contact with an electrical device. If contact was broken between the wire and the source of electricity, and the wire was touched with the other hand, a discharge took place that was experienced as a violent shock.
If a charge Q is placed on the metal plates, the voltage rises to amount V. The measure of a capacitor's ability to store charge is the capacitance C, where C = Q/V. Charge flows from a capacitor just as it flows from a battery, but with one significant difference. When the charge leaves a capacitor's plates, no more can be obtained without recharging. This happens because the electrical force is conservative. The energy released cannot exceed the energy stored. The ability to do work is called electric potential.
A type of conservation of energy is also associated with emf. The electrical energy obtainable from a battery is limited by the energy stored in chemical molecular bonds. Both emf and electric potential are measured in volts, and, unfortunately, the terms voltage, potential, and emf are used rather loosely. For example, the term battery potential is often used instead of emf.
1747 - Vitreous Electricity, Conservation of Charge
Benjamin Franklin (1706-90) was an American printer, author, philosopher, diplomat, scientist, and inventor.
After Gilbert's 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. (William Watson (1715-87) in England independently reached the same conclusion.) To identify these two forces, he gave the names, positive and negative charges and to symbolize them, he used the + and - signs the + being for positive and the - for negative. Benjamin Franklin realized that all materials possess a single kind of electrical "fluid" that can penetrate matter freely but that can be neither created nor destroyed. The action of rubbing merely transfers the fluid from one body to another, electrifying both. Franklin and Watson originated the principle of conservation of charge: the total quantity of electricity in an insulated system is constant. Franklin defined the fluid, which corresponded to vitreous electricity, as positive and the lack of fluid as negative. Therefore, according to Franklin, the direction of flow was from positive to negative--the opposite of what is now known to be true. A subsequent two-fluid theory was developed, according to which samples of the same type attract, whereas those of opposite types repel.
Franklin was acquainted with the Leyden jar (a glass jar coated inside and outside with tinfoil), how it could store a charge and how it caused a shock when it was discharged. Franklin wondered whether lightning and thunder were also a result of electrical discharges. During a thunderstorm in 1752, Franklin flew a kite that had a metal tip. At the end of the wet, conducting hemp line on which the kite flew he attached a metal key, to which he tied a nonconducting silk string that he held in his hand. The experiment was extremely hazardous, but the results were unmistakable: when he held his knuckles near the key, he could draw sparks from it. The next two who tried this extremely dangerous experiment were killed.
1750 - First Book on Magnet Manufacture
John Mitchell publishes the first book on making steel magnets.
1757 - Power, Steam Engine
James Watt(1736-1819) conducted no electrical experiments. He was an instrument maker by trade and set up a repair shop in Glasgow in 1757. Watt measured the rate of work exerted by a horse drawing rubbish up an old mine shaft and found it amounted to about 22,000 ft-lbs per minute. He added a margin of 50% arriving at 33,000 ft-lbs is equal to one horse-power.
James Watt, also invented the steam condensing engine. His improvements to steam engines were patented over a period of 15 years, starting in 1769 and his name was given to the electric unit of power, the Watt. When Edison's generator was coupled with Watt's steam engine, large scale electricity generation became a practical proposition.
1767 - Electrical Force
It was known as early as 1600 that the attractive or repulsive force diminishes as the charges are separated. This relationship was first placed on a numerically accurate, or quantitative, foundation by Joseph Priestley, a friend of Benjamin Franklin. In 1767, Priestley indirectly deduced that when the distance between two small, charged bodies is increased by some factor, the forces between the bodies is reduced by the square of the factor. For example, if the distance between charges is tripled, the force decreases to one-ninth its former value. Although rigorous, Priestley's proof was so simple that he did not strongly advocate it. The matter was not considered settled until 18 years later, when John Robinson of Scotland made more direct measurements of the electrical force involved.
1780 - Electric Current
Because of an accident the 18th-century Italian scientist Luigi Galvani started a chain of events that culminated in the development of the concept of voltage and the invention of the battery. In 1780 one of Galvani's assistants noticed that a dissected frog leg twitched when he touched its nerve with a scalpel. Another assistant thought that he had seen a spark from a nearby charged electric generator at the same time. Galvani reasoned that the electricity was the cause of the muscle contractions. He mistakenly thought, however, that the effect was due to the transfer of a special fluid, or "animal electricity," rather than to conventional electricity.
Experiments such as this, in which the legs of a frog or bird were stimulated by contact with different types of metals, led Luigi Galvani in 1791 to propose his theory that animal tissues generate electricity. In experimenting with what he called atmospheric electricity, Galvani found that a frog muscle would twitch when hung by a brass hook on an iron lattice.
1792 - Electrochemistry, Voltaic Cell
By 1792 another Italian scientist, Alessandro Volta, disagreed: he realized that the main factors in Galvani's discovery were the two different metals - the steel knife and the tin plate - upon which the frog was lying. the different metals, separated by the moist tissue of the frog, were generating electricity. The frog's leg was simply a detector.
In 1800,Volta showed that when moisture comes between two different metals, electricity is created. This led him to invent the first electric battery, the voltaic pile, which he made from thin sheets of copper and zinc separated by moist pasteboard (felt soaked in brine).
In this way, a new kind of electricity was discovered, electricity that flowed steadily like a current of water instead of discharging itself in a single spark or shock. Volta showed that electricity could be made to travel from one place to another by wire, thereby making an important contribution to the science of electricity.
1820 - Electromagnetism, Current
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.
Andre Marie Ampere, a French mathematician who devoted himself to the study of electricity and magnetism, was the first to explain the electro-dynamic theory. He showed that two parallel wires, carrying current, attracted each other if the currents flowed in the same direction and opposed each other if the currents flowed in opposite directions. He formulated in mathematical terms, the laws that govern the interaction of 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. An electric charge in motion is called electric current. The strength of a current is the amount of charge passing a given point per second, or I = Q/t, where Q coulombs of charge passing in t seconds. The unit for measuring current is the ampere or amp, where 1 amp = 1 coulomb/sec. Because it is the source of magnetism as well, current is the link between electricity and magnetism.
1822 - Fourier Transforms
Baron Joseph Fourier (1768-1830) was a French mathematician. His method of analyzing waves, published in 1822, was a spinoff of his work on the flow of heat. It shows how any wave can be built up from simpler waves. This powerful branch of mathematics, Fourier Transforms has contributed to important modern developments like electronic speech recognition.
1826 - Resistance - Currents Causing Heat
In 1826, the German Physicist Georg Simon Ohm, examined Volta's Principle of the electric battery and Ampere's relationship of currents in a circuit. He noted that when there was a current in a circuit, there was at times, heat, and the amount of heat was related to different metals. He discovered that there was a 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.
1830 - Inductance
In 1830, Joseph Henry (1797-1878), discovered that a change in magnetism can make currents flow, but he failed to publish this. In 1832 he described self-inductance - the basic property of inductor. In recognition of his work, inductance is measured in henries. The stage was then set for the encompassing electromagnetic theory of James Clerk Maxwell. The variation of actual currents is enormous. A modern electrometer can detect currents as low as 1/100,000,000,000,000,000 amp, which is a mere 63 electrons per second. The current in a nerve impulse is approximately 1/100,000 amp; a 100-watt light bulb carries 1 amp; a lightning bolt peaks at about 20,000 amps; and a 1,200-megawatt nuclear power plant can deliver 10,000,000 amps at 115 V.
1836 - Daniell Cell
In 1836, John Daniell (1790-1845) proposed an improved electric cell that supplied an even current during continuous operation. The Daniell cell gave new impetus to electric research and found many commercial applications. In 1837 Daniell was presented the highest award of the Royal Society, the Copley Medal, for the invention of the Daniell cell.
1837 - Telegraph, Electromagnet
After the electric battery and the electromagnet were discovered, Samuel Morse(1791-1872) introduced the electric telegraph. Coded messages were sent over wires, by means of electrical impulses (identified as dots and dashes) known as Morse code. This was really the beginning of commercially used electricity. The electric telegraph is known as the first practical use of electricity and the first system of electrical communication. It is interesting to note here, that the Post Office in Australia, played an important part at that time, in the organizing of the communication.
1840 - Mechanical Computer
Charles Babbage (1791-1871), a British mathematician, designed several machines to generate error-free tables for navigation. The mechanical devices would serve as models for the later electronic computers.
1850 - Thermoelectricity
Thomas Seebeck a German physicist was the discover of the "Seebeck effect". He twisted two wires made of different metals and heated a junction where the two wires met, producing a small current. The current is the result of a flow of heat from the hot to the cold junction. This is called thermoelectricity. Thermo is a Greek word meaning heat.
1854 - Boolean Algebra
George Boole was entirely self taught. He published a way of using symbols that perfectly expresses the rules of logic. Using this system, complicated rules can be written clearly and often simplified.
1855 - Electromagnetic Induction
Michael Faraday (1791-1867) an Englishman, made one of the most significant discoveries in the history of electricity: Electromagnetic induction. His pioneering work dealt with how electric currents work. Many inventions would come from his experiments, but they would come fifty to one hundred years later. Failures never discouraged Faraday. He would say; "the failures are just as important as the successes." He felt failures also teach. The farad, the unit of capacitance is named in the honor of Michael Faraday.
Faraday was greatly interested in the invention of the electromagnet, but his brilliant mind took earlier experiments still further. If electricity could produce magnetism, why couldn't magnetism produce electricity. In 1831, Faraday found the solution. Electricity could be produced through magnetism by motion. He discovered that when a magnet was moved inside a coil of copper wire, a tiny electric current flows through the wire. 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.
1860 - Arc Lights
As the practical use of electricity became evident and the electric telegraph was in operation, it was not long before scientists were looking towards making further use of this electricity. 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 incandescence, 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.
1860 - DC Motor
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.
1866 - LeClanche Cell
Leclanche (1839-1882) is a French engineer who in about 1866 invented the battery that bears his name. In slightly modified form, the Leclanché battery, now called a dry cell, is produced in great quantities and is widely used in devices such as flashlights and portable radios. This cell consists of a zinc case filled with a moist paste containing ammonium sulfate. In the center of this electrolyte paste is a carbon rod coated with manganese dioxide, which is a strong oxidizing agent.
1871 - DC Generator
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. In 1831, Michael Faraday 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, thus the electric generator could now be developed. 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, Edison had completed the design of the system we still use to distribute electricity from power stations.
1876 - Telephone
Since the telegraph was invented by Samual Morse in 1837, great advances had been made in its utilization, but it continued as a telegraph system using Morse Code for its communication. Alexander Graham Bell in 1875, was interested in telegraphy and realized 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 honor of inventing the "telephone".
Alexander Graham Bell (1847-1922) born in Scotland, was raised in a family that was interested and involved in the science of sound. Bell's father and grandfather both taught speech to the deaf. A unit of sound level is called a bel in his honor. Sound levels are measured in tenths of a bel, or decibels. The abbreviation for decibel is dB.
1879 - DC Generation, Incandescent Light
Thomas Alva Edison, (1847-1931)was one of the most well known inventors of all time with 1093 patents. Self-educated, Edison was interested in chemistry and electronics. During the whole of his life, Edison received only three months of formal schooling, and was dismissed from school as being retarded, though in fact a childhood attack of scarlet fever had left him partially deaf.
Nearly 40 years went by before a really practical DC (Direct Current) generator was built by Thomas Edison. Edison's many inventions included the phonograph and an improved printing telegraph. In 1878 Joseph Swan, a British scientist, invented the incandescent filament lamp and within twelve months Edison made a similar discovery in America. Swan and Edison later set up a joint company to produce the first practical filament lamp. Prior to this, electric lighting had been my crude arc lamps.
Edison used his DC generator to provide electricity to light his laboratory and later to illuminate the first New York street to be lit by electric lamps, in September 1882. Edison's successes were not without controversy, however - although he was convinced of the merits of DC for generating electricity, other scientists in Europe and America recognized that DC brought major disadvantages.
1880 - Heaviside Layer
Oliver Heaviside (1850-1925) The British mathematician realized that information travels along a cable as a wave in the space between the conductors, rather than through the conductors themselves. His concepts made it possible to design long-distance telephone cables. He also discovered why radio waves bend around the Earth. This led to long-range radio reception.
1880 - Absolute Temperatures, Kirchoff's Laws, Coulomb's Laws, Magnetic Flux, Microphone
William Thomson, Lord Kelvin (1824-1907) was best known in his invention of a new temperature scale based on the concept of an absolute zero of temperature at -273°C (-460°F). To the end of his life, Thomson maintained fierce opposition to the idea that energy emitted by radioactivity came from within the atom. One of the greatest scientific discoveries of the 19th century, Thomson died opposing one of the most vital innovations in the history of science.
Moskowitz, L. R.: Permanent Magnet Design and Application Handbook, Cahners Books International, Inc. (1976)
The above is the history of the development of magnetism and electricity, hope that AOMAG Magnetics summary organization is helpful to you.