I. Read the texts.

Outstanding Scientists

The first discoveries of electricity were made back in ancient Greece. Greek philosophers discovered that when amber is rubbed against cloth, lightweight objects will stick to it. This is the basis of static electricity.

Over the centuries, there have been many discoveries made about electricity. We've all heard of famous people like Benjamin Franklin and Thomas Edison, but there have been many other inventors throughout history that were each a part in the development of electricity.

Volta

Speaking of electricity in motion, reference should be made to Volta, professor of natural history, at the University of Pavia, Italy. Volta was a clever experimentalist, with a thorough knowledge of all that had been done by others in the field of electricity, a great scientist. In 1800, he constructed the first source of steady, continuous current – the voltaic pile. The voltaic pile was the first battery transforming chemical energy into electrical energy. It is to this invention that we owe the development of modern electrical science and industry.

Georg Simon Ohm

Georg Simon Ohm (16 March 1789 – 6 July 1854) was a German physicist. As a high school teacher, Ohm began his research with the recently invented electrochemical cell, invented by Italian Count Alessandro Volta. Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential differene (voltage) applied across a conductor and the resultant electric current – now known as Ohm's law.

Using the results of his experiments, Ohm was able to define the fundamental relationship among voltage, current, and resistance, which represents the true beginning of electrical circuit analysis.

Georg Simon Ohm was born at Erlangen, Bavaria, son to Johann Wolfgang Ohm, a locksmith and Maria Elizabeth Beck, the daughter of a tailor in Erlangen. They were a Protestant family. Although his parents had not been formally educated, Ohm's father was a respected man who had educated himself to a high level and was able to give his sons an excellent education through his own teachings. Some of Ohm's brothers and sisters died in their childhood, only three survived. The survivors, including Georg Simon, were his younger brother Martin, who later became a well-known mathematician, and his sister Elizabeth Barbara. His mother died when he was ten.

Ohm's law, that electric current is proportional to a potential difference, was first discovered by Henry Cavendish, but Cavendish did not publish his electrical discoveries in his lifetime and they did not become known until 1879, long after Ohm had independently made the discovery and published himself. Thus the law came to bear the name of Ohm.

James Joule

A few years after Georg Ohm made his discovery, the English physicist James Joulemade his own investigation of how electrical energy works. Joule was interested in how one form of energy can be converted to another. One of the changes he studied was the conversion of electrical energy to heat.

Joule found that the amount of power in an electric circuit depends on two things: the voltage of the circuit and the amount of current flowing in it. The more current a circuit has, the more power it delivers. And the more voltage a circuit has, the more power it delivers. The power produced by a circuit can be calculated by multiplying the voltage times the amount of current:

This rule is known as Joule’s law. It tells us that increasing either the current or the voltage in a circuit increases the power that the circuit produces.

Benjamin Franklin

Benjamin Franklin was a great American statesman, writer, and inventor but he was also an early investigator of electricity. Franklin realized that electricity could be explained just as easily with one fluid as with two. Positive charge could be considered to be an extra amount of the fluid. Negative charge would then be a shortage of the same substance. The fluid theory didn’t last, but Franklin’s idea of positive and negative charges being two sides of a single force did.

Franklin also recognized a very important law of electricity: the law of conservation of charge. It says that for every negative charge created, there must be an equal amount of positive charge. That means that the total of all positive and negative charges in the universe must balance each other perfectly.

The law of conservation of charge doesn’t mean that we can’t have any electricity. But whenever we unbalance electrical forces, we must create positive and negative charges in equal amounts. For example, you can create an electrical charge by rubbing an inflated balloon against a wool sweater. The balloon will pick up a slight negative charge from the wool. But the wool will also receive an equal amount of positive charge. The balloon will then stick to a wall because of the difference in electrical charge between the wall and the balloon.

Hans Christian Orsted

The next important discovery about electricity was made by Hans Christian Orstedin 1820. He connected a wire to a battery to make an electric circuit. A magnetic compass happened to be sitting on the laboratory table nearby. Orsted noticed that when electricity was flowing through the wire, the compass needle was attracted to it.

After more experimenting, Orsted was sure of his discovery: a moving electrical charge creates magnetic force. Whenever an electric current flows through a wire, it creates magnetic forces around the wire.

After 1820 the study of electricity and magnetism moved at a very rapid rate. Orsted had found that electricity could exert enough force to make a magnetic needle spin in a compass. Stronger electric currents and stronger magnets could be combined to spin a motor. Using Orsted’s discovery, the first electromagnet and the first electric motor were both built by 1823.

Michael Faraday

Michael Faraday was born in a small village near London. His father, a poor blacksmith, could feed and clothe his family with difficulty but was entirely unable to afford the luxury of an education for his boy. Michael had to work, and he had to learn a trade. When a boy of 13, he became an errand-boy and later on a bookbinder’s apprentice.

Some of the scientific books passing through his hands aroused the boy’s interest in science.

Finding the apprentice studying electricity, a visitor to the bookbinder’s shop gave him tickets to attend four lectures by Humphry Davy. While at the lectures, Faraday listened, understood everything and put down every word. Then, at home, in his room, he wrote Davy a letter, telling him of his great interest in science and his desire to do scientific work. The notes of the lectures were enclosed as proof of his earnestness.

They say that Davy was a scientist well known for his researches and discoveries but his greatest discovery was Michael Faraday.

In March 1813, Davy took him as a laboratory assistant at the Royal Institution. Later he assisted Davy in his research, started to write articles for scientific magazines and to carry on experimental work.

In his lifetime, Faraday performed more than two thousand laborious experiments and made countless valuable discoveries in chemistry and physics.

One of his most important discoveries is the generation of electricity from magnetism. On the very day on which the report of Orsted’s discovery was published in England, Faraday repeated the latter’s experiments and confermed his results. Even at that early date, the fact that electricity could produce magnetic effects turned his thoughts towards the reverse possibility – that of generating electricity owing to magnetic effects.

Faraday wound a copper wire into a coil, and to this wire he connected a galvanometer in order to detect any current which might be generated. He observed the galvanometer needle move both while plunging a bar magnet into the hollow coil and while lifting it out. Evidently, electricity had been produced in the coil. But why had his previous experiments failed? It was because his magnets, wires, and coils had been stationary. It was only when the magnet was moving that an electric current was generated. When the magnet was still, no electricity flowed. From this experiment came what is known as Faraday’s law: a moving magnetic field creates an electric current in a wire.

As known all over the world, on October 1831, Faraday made his historic discovery, namely, induction of a current in a conductor resulted when the conductor was made to cut the lines of magnetic force.

Thomas Alva Edison

Thomas Alva Edison (February 11, 1847 – October 18, 1931) was an American inventor, scientist, and businessman who developed many devices that greatly influenced life around the world, including the phonograph, the motion picture camera, and a long-lasting, practical electric light bulb. He was one of the first inventors to apply the principles of mass production and large teamwork to the process of invention.

Edison is credited with numerous inventions that contributed to mass communication and, in particular, telecommunications. These included a stock ticker, a mechanical vote recorder, a battery for an electric car, electrical power, recorded music and motion pictures.

Thomas Edison was born in Milan, Ohio and grew up in Port Huron, Michigan. He was the seventh and last child of Samuel Ogden Edison, Jr.

Edison developed hearing problems at an early age. The cause of his deafness has been attributed to a bout of scarlet fever during childhood and recurring untreated middle-ear infections.

Thomas Edison began his career as an inventor in Newark, New Jersey, with the automatic repeater and his other improved telegraphic devices, but the invention which first gained him notice was the phonograph in 1877. This accomplishment was so unexpected by the public at large as to appear almost magical.

Edison did not invent the first electric light bulb, but instead invented the first commercially practical incandescent light.

After many experiments with platinum and other metal filaments, Edison returned to a carbon filament. The first successful test was on October 22, 1879.

Edison is credited with designing and producing the first commercially available fluoroscope, a machine that uses X-rays to take radiographs. Until Edison discovered that calcium tungstate fluoroscopy screens produced brighter images than the barium platinocyanide screens originally used by Wilhelm Röntgen, the technology was capable of producing only very faint images. The fundamental design of Edison's fluoroscope is still in use today, despite the fact that Edison himself abandoned the project after nearly losing his own eyesight and seriously injuring his assistant, Clarence Dally.

The key to Edison's fortunes was telegraphy. With knowledge gained from years of working as a telegraph operator, he learned the basics of electricity. This allowed him to make his early fortune with the stock ticker, the first electricity-based broadcast system. Edison patented the sound recording and reproducing phonograph in 1878.

Nikola Tesla

Nikola Tesla (10 July 1856 – 7 January 1943) was an inventor, mechanical engineer, and electrical engineer. He is best known for his many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries. Tesla's patents and theoretical work formed the basis of modern alternating current (AC) electric power systems, including the polyphase system of electrical distribution and the AC motor.

Tesla was born in the village of Smiljan and later became an American citizen. Because of his demonstration of wireless communication through radio he was widely respected as one of the greatest electrical engineers who worked in America. He pioneered modern electrical engineering and many of his discoveries were of groundbreaking importance. In the United States during this time, Tesla's fame rivaled that of any other inventor or scientist in history or popular culture. Tesla demonstrated wireless energy transfer to power electronic devices as early as 1893, and aspired to intercontinental wireless transmission of industrial power in his unfinished Wardenclyffe Tower project.

In addition to his work on electromagnetism and electromechanical engineering, Tesla contributed in varying degrees to the establishment of robotics, remote control, radar, and computer science, and to the expansion of ballistics, nuclear physics, and theoretical physics.

Tesla engaged in reading many works, memorizing complete books, supposedly having a photographic memory.

In 1886, Tesla formed his own company, Tesla Electric Light & Manufacturing. In 1887, he constructed the initial brushless alternating current induction motor,later he developed the principles of his Tesla coil. In April 1887, Tesla began investigating what would later be called X-rays using his own single terminal vacuum tubes. This device differed from other early X-ray tubes in that it had no target electrode. We now know that this device operated by emitting electrons from the single electrode through a combination of field electron emission and thermionic emission. Once liberated, electrons are strongly repelled by the high electric field near the electrode during negative voltage peaks from the oscillating HV output of the Tesla Coil, generating X rays as they collide with the glass envelope.

Tesla demonstrated wireless energy transmission as early as 1891. The Tesla effect is a term for an application of this type of electrical conduction (that is, the movement of energy through space and matter, not just the production of voltage across a conductor).

When Tesla was 36 years old, the first patents concerning the polyphase power system were granted. He continued research of the system and rotating magnetic field principles. From 1893 to 1895, he investigated high frequency alternating currents. He generated AC of one million volts using a conical Tesla coil and investigated the skin effect in conductors, designed tuned circuits, invented a machine for inducing sleep, cordless gas discharge lamps, and transmitted electromagnetic energy without wires, building the first radio transmitter. He described and demonstrated in detail its principles.

Tesla also explained the principles of the rotating magnetic field and induction motor by demonstrating how to make an egg made of copper stand on end in his demonstration of the device he constructed known as the “Egg of Columbus”.

The Tesla generator was developed by Tesla in 1895, in conjunction with his developments concerning the liquefaction of air. Tesla knew, from Lord Kelvin's discoveries, that more heat is absorbed by liquefied air when it is re-gasified and used to drive something, than is required by theory; in other words, that the liquefaction process is somewhat anomalous or “over unity”.

A “world system” for “the transmission of electrical energy without wires” that depends upon the electrical conductivity of the earth was proposed, in which transmission in various natural media with current that passes between the two points are used to power devices. In a practical wireless energy transmission system using this principle, a high-power ultraviolet beam might be used to form a vertical ionized channel in the air directly above the transmitter-receiver stations. The same concept is used in virtual lightning rods, the electrolaser electroshock weapon, and has been proposed for disabling vehicles.

At his lab, Tesla proved that the earth was a conductor, and he produced artificial lightning (with discharges consisting of millions of volts, and up to 135 feet long). Tesla also investigated atmospheric electricity, observing lightning signals via his receivers.

Tesla worked on plans for a directed-energy weapon from the early 1900s until his death. In 1937, Tesla wrote a treatise entitled “The Art of Projecting Concentrated Non-dispersive Energy through the Natural Media”, which concerned charged particle beams. Tesla published the document in an attempt to expound on the technical description of a “superweapon” that would put an end to all war. It describes an open-ended vacuum tube with a gas jet seal that allows particles to exit, a method of charging particles to millions of volts, and a method of creating and directing nondispersive particle streams.

Tesla was fluent in eight languages. Along with Serbian, he spoke Czech, English, French, German, Hungarian, Italian, and Latin.

James Watt

James Watt, (19 January 1736 – 25 August 1819) was a Scottish inventor and mechanical engineer whose improvements to the Newcomen steam engine were fundamental to the world.

While working as an instrument maker at the University of Glasgow, Watt became interested in the technology of steam engines. He realised that contemporary engine designs wasted a great deal of energy by repeatedly cooling and re-heating the cylinder. Watt introduced a design enhancement, the separate condenser, which avoided this waste of energy and radically improved the power, efficiency, and cost-effectiveness of steam engines. He developed the concept of horsepower. The SI unit of power, the watt, was named after him.

Over the next six years, he made a number of other improvements and modifications to the steam engine. A double acting engine, in which the steam acted alternately on the two sides of the piston was one. He described methods for working the steam “expansively” (i.e., using steam at pressures well above atmospheric). A compound engine, which connected two or more engines was described. Another important invention, one of which Watt was most proud of, was the Parallel motion which was essential in double-acting engines as it produced the straight line motion required for the cylinder rod and pump, from the connected rocking beam, whose end moves in a circular arc.

Because of the danger of exploding boilers, which were in a very primitive stage of development, and the ongoing issues with leaks, Watt restricted his use of high pressure steam – all of his engines used steam at near atmospheric pressure.

Watt continued to invent other things before and during his semi-retirement. He invented a new method of measuring distances by telescope, improvements in the oil lamp, a steam mangle and a machine for copying sculptures. Within his home in Handsworth Heath, Staffordshire, Watt made use of a garret room as a workshop, and it was here that he worked on many of his inventions.

André-Marie Ampère

André-Marie Ampère (20 January 1775 – 10 June 1836) was a French physicist and mathematician who is generally regarded as one of the main discoverers of electromagnetism. The SI unit of measurement of electric current, the ampere, is named after him.

Ampère was born in Lyon, France on 20 January 1775. His father began to teach him Latin, until he discovered the boy's preference and aptitude for mathematical studies.

Ampère's fame mainly rests on his establishing the relations between electricity and magnetism, and in developing the science of electromagnetism, or, as he called it, electrodynamics. On 11 September 1820 he heard of H. C. Ørsted's discovery that a magnetic needle is acted on by a voltaic current. Only a week later, on 18 September, Ampère presented a paper to the Academy containing a much more complete exposition of that and kindred phenomena. On the same day, Ampère also demonstrated before the Academy that parallel wires carrying currents attract or repel each other, depending on whether currents are in the same (attraction) or in opposite directions (repulsion). This laid the foundation of electrodynamics. Ampère was appointed professor of mathematics at the University of Lyon.

The topic of electromagnetism thus begun, Ampère developed a mathematical theory which not only described the electromagnetic phenomena already observed, but also predicted many new ones.

Georg Simon Ohm

Georg Simon Ohm (16 March 1789 – 6 July 1854) was a German physicist. As a high school teacher, Ohm began his research with the recently invented electrochemical cell, invented by Italian Count Alessandro Volta. Using equipment of his own creation, Ohm determined that there is a direct proportionality between the potential difference (voltage) applied across a conductor and the resultant electric current. This relationship is now known as Ohm's law.

Georg Simon Ohm was born at Erlangen, Bavaria. Although his parents had not been formally educated, Ohm's father was a respected man who had educated himself to a high level and was able to give his sons an excellent education through his own teachings.

From early childhood, Georg and Martin were taught by their father who brought them to a high standard in mathematics, physics, chemistry and philosophy. His father sent Ohm to Switzerland where, in September 1806, he took up a post as a mathematics teacher in a school.

His studies had stood him in good position for his receiving a doctorate from Erlangen on 25 October 1811 and immediately joined the staff as a mathematics lecturer. Luckily, the physics lab was well-equipped, so Ohm devoted himself to experimenting on physics.

Ohm's law first appeared in 1827. He gave his complete theory of electricity in the book. It begins with the mathematical background necessary for an understanding of the rest of the work. While his work greatly influenced the theory and applications of current electricity, it was coldly received at that time.

Joseph Henry

Joseph Henry (17 December 1797 – 13 May 1878) was an American scientist, a founding member of the National Institute for the Promotion of Science, a precursor of the Smithsonian Institution. During his lifetime, he was highly regarded. While building electromagnets, Henry discovered the electromagnetic phenomenon of self-inductance. He also discovered mutual inductance independently of Michael Faraday, though Faraday was the first to publish his results. The SI unit of inductance, the henry, is named in his honor. Henry's work on the electromagnetic relay was the basis of the electrical telegraph, invented by Samuel Morse and Charles Wheatstone separately.

Henry was born in Albany, New York. His parents were poor, and Henry's father died while he was still young. For the rest of his childhood, Henry lived with his grandmother in Galway, New York. His interest in science was sparked at the age of sixteen by a book of lectures on scientific topics titled Popular Lectures on Experimental Philosophy. In 1819 he entered The Albany Academy, where he was given free tuition. Henry excelled at his studies (so much that he would often be helping his teachers teach science) and in 1826 he was appointed Professor of Mathematics and Natural Philosophy at The Albany Academy. Some of his most important research was conducted in this new position. His curiosity about terrestrial magnetism led him to experiment with magnetism in general. He was the first to coil insulated wire tightly around an iron core in order to make a more powerful electromagnet, improving on William Sturgeon's electromagnet which used loosely coiled uninsulated wire. Using this technique, he built the strongest electromagnet at the time for Yale. He also showed that, when making an electromagnet using just two electrodes attached to a battery, it is best to wind several coils of wire in parallel, but when using a set-up with multiple batteries, there should be only one single long coil. The latter made the telegraph feasible.

Using his newly-developed electromagnetic principle, Henry in 1831 created one of the first machines to use electromagnetism for motion. This was the earliest ancestor of modern DC motor. It did not make use of rotating motion, but was merely an electromagnet perched on a pole, rocking back and forth. The rocking motion was caused by one of the two leads on both ends of the magnet rocker touching one of the two battery cells, causing a polarity change, and rocking the opposite direction until the other two leads hit the other battery.

This apparatus allowed Henry to recognize the property of self inductance. British scientist Michael Faraday also recognized this property around the same time; since Faraday published his results first, he became the officially recognized discoverer of the phenomenon.

Heinrich Rudolf Hertz

Heinrich Rudolf Hertz (February 22, 1857 – January 1, 1894) was a German physicist who clarified and expanded the electromagnetic theory of light that had been put forth by Maxwell. He was the first to satisfactorily demonstrate the existence of electromagnetic waves by building an apparatus to produce and detect VHF or UHF radio waves.

Hertz waz born in Hamburg, Germany. While studying at the Gelehrtenschule des Johanneums in Hamburg, he showed an aptitude for sciences and engineering. In 1880, Hertz obtained his PhD from the University of Berlin; and remained for post-doctoral study under Helmholtz. In 1883, Hertz took a post as a lecturer in theoretical physics at the University of Kiel. In 1885, Hertz became a full professor at the University of Karlsruhe where he discovered electromagnetic waves.

The most dramatic prediction of Maxwell's theory of electromagnetism, published in 1865, was the existence of electromagnetic waves moving at the speed of light, and the conclusion that light itself was just such a wave. This challenged experimentalists to generate and detect electromagnetic radiation using some form of electrical apparatus.

The first clearly successful attempt was made by Heinrich Hertz in 1886. For his radio wave transmitter he used a high voltage induction coil, a condenser (capacitor, Leyden jar) and a spark gap – whose poles on either side are formed by spheres of 2 cm radius – to cause a spark discharge between the spark gap’s poles oscillating at a frequency determined by the values of the capacitor and the induction coil.

To prove there really was radiation emitted, it had to be detected. Hertz used a piece of copper wire, 1 mm thick, bent into a circle of a diameter of 7.5 cm, with a small brass sphere on one end, and the other end of the wire was pointed, with the point near the sphere. He added a screw mechanism so that the point could be moved very close to the sphere in a controlled fashion. This “receiver” was designed so that current oscillating back and forth in the wire would have a natural period close to that of the “transmitter” described above. The presence of oscillating charge in the receiver would be signaled by sparks across the (tiny) gap between the point and the sphere (typically, this gap was hundredths of a millimeter).

In more advanced experiments, Hertz measured the velocity of electromagnetic radiation and found it to be the same as the light’s velocity. He also showed that the nature of radio waves’ reflection and refraction was the same as those of light, and established beyond any doubt that light is a form of electromagnetic radiation obeying the Maxwell equations.

Summing up Hertz's importance: his experiments would soon trigger the invention of the wireless telegraph and radio by Marconi and others and TV.

In recognition of his work, the unit of frequency – one cycle per second – is named the “hertz”, in honor of Heinrich Hertz.

In 1892, an infection was diagnosed (after a bout of severe migraines) and Hertz underwent some operations to correct the illness. He died of Wegener's granulomatosis at the age of 36 in Bonn, Germany in 1894, and was buried in Ohlsdorf, Hamburg.

Heinrich Hertz was honored by a number of countries around the world.

Marie Skłodowska Curie

Marie Skłodowska Curie (7 November 1867 – 4 July 1934) was a Polish-born French physicist and chemist famous for her work on radioactivity. She was a pioneer in the field of radioactivity and the first person honored with two Nobel Prizes—in physics and chemistry. She was also the first female professor at the University of Paris.

She was born Maria Skłodowska in Warsaw and lived there until she was twenty-four. In 1891, she followed her older sister Bronisława to study in Paris, where she obtained her higher degrees and conducted her subsequent scientific work. She founded the Curie Institutes in Paris and Warsaw. Her husband Pierre Curie shared her Nobel prize in physics. Her daughter Irène Joliot-Curie and son-in-law, Frédéric Joliot-Curie, also shared a Nobel prize. She was the sole winner of the 1911 Nobel Prize for Chemistry. Curie was the first woman to win a Nobel Prize, and she is the only woman to win the award in two different fields.

Her achievements include the creation of a theory of radioactivity (a term she coined), techniques for isolating radioactive isotopes, and the discovery of two new elements, polonium and radium. Under her direction, the world's first studies were conducted into the treatment of neoplasms (cancers) using radioactive isotopes.

While an actively loyal French citizen, she never lost her sense of Polish identity. She named the first new chemical element that she discovered polonium (1898) for her native country, and in 1932 she founded a Radium Institute (now the Maria Skłodowska–Curie Institute of Oncology) in her home town, Warsaw, headed by her physician sister Bronisława.

Pierre Curie was an instructor at the School of Physics and Chemistry. Skłodowska had begun her scientific career in Paris with an investigation of the magnetic properties of various steels; it was their mutual interest in magnetism that drew Skłodowska and Curie together.

In 1896, Henri Becquerel discovered that uranium salts emitted rays that resembled X-rays in their penetrating power. He demonstrated that this radiation, unlike phosphorescence, did not depend on an external source of energy, but seemed to arise spontaneously from uranium itself. Becquerel had, in fact, discovered radioactivity.

Skłodowska–Curie decided to look into uranium rays as a possible field of research for a thesis. She used a clever technique to investigate samples. Fifteen years earlier, her husband and his brother had invented the electrometer, a sensitive device for measuring electrical charge. Using the Curie electrometer, she discovered that uranium rays caused the air around a sample to conduct electricity. Using this technique, her first result was the finding that the activity of the uranium compounds depended only on the quantity of uranium present. She had shown that the radiation was not the outcome of some interaction of molecules, but must come from the atom itself. In scientific terms, this was the most important single piece of work that she conducted.

As they were unaware of the deleterious effects of radiation exposure attendant on their chronic unprotected work with radioactive substances, Skłodowska–Curie and her husband had no idea what price they would pay for the effect of their research upon their health.

During World War I, Skłodowska-Curie pushed for the use of mobile radiography units, which came to be popularly known as petites Curies (“Little Curies”), for the treatment of wounded soldiers. These units were powered using tubes of radium emanation, a colorless, radioactive gas given off by radium, later identified as radon. Skłodowska-Curie provided the tubes of radium, derived from the material she purified. Also, promptly after the war started, she donated the gold Nobel Prize medals she and her husband had been awarded, to the war effort.

On July 4, 1934, Skłodowska-Curie died at the Sancellemoz Sanatorium in Passy, in Haute-Savoie, eastern France, from aplastic anemia, which was almost certainly contracted from exposure to radiation. The damaging effects of ionizing radiation were not then known, and much of her work had been carried out in a shed, without proper safety measures. She had carried test tubes containing radioactive isotopes in her pocket and stored them in her desk drawer, remarking on the pretty blue-green light that the substances gave off in the dark.

Because of their levels of radioactivity, her papers from the 1890s are considered too dangerous to handle. Even her cookbook is highly radioactive. They are kept in lead-lined boxes, and those who wish to consult them must wear protective clothing.

The result of the Curies' work was epoch-making. Radium's radioactivity was so great that it could not be ignored. It seemed to contradict the principle of the conservation of energy and therefore forced a reconsideration of the foundations of physics. On the experimental level the discovery of radium provided men like Ernest Rutherford with sources of radioactivity with which they could probe the structure of the atom. As a result of Rutherford's experiments with alpha radiation, the nuclear atom was first postulated. In medicine, the radioactivity of radium appeared to offer a means by which cancer could be successfully attacked.

William Thomson

William Thomson, 1st Baron Kelvin (26 June 1824 – 17 December 1907) was a mathematical physicist and engineer. At the University of Glasgow he did important work in the mathematical analysis of electricity and formulation of the first and second Laws of Thermodynamics, and did much to unify the emerging discipline of physics in its modern form. For his work on the transatlantic telegraph project he was knighted by Queen Victoria, becoming Sir William Thomson. On his ennoblement in honour of his achievements in thermodynamics, and of his opposition to Irish Home Rule, he adopted the title Baron Kelvin of Largs and is therefore often described as Lord Kelvin. The title refers to the River Kelvin, which flows close by his laboratory at the university of Glasgow, Scotland.

Lord Kelvin is widely known for realising that there was a lower limit to temperature, absolute zero; absolute temperatures are stated in units of kelvin in his honour. He predicted that the melting point of ice must fall with pressure, otherwise its expansion on freezing could be exploited in a perpetuum mobile. Experimental confirmation in his laboratory did much to bolster his beliefs. In 1848, he extended the Carnot–Clapeyron theory still further through his dissatisfaction that the gas thermometer provided only an operational definition of temperature. He proposed an absolute temperature scale in which a unit of heat descending from a body A at the temperature T° of this scale, to a body B at the temperature (T−1)°, would give out the same mechanical effect [work], whatever be the number T. Such a scale would be quite independent of the physical properties of any specific substance. By employing such a “waterfall”, Thomson postulated that a point would be reached at which no further heat (caloric) could be transferred, the point of absolute zero about which Guillaume Amontons had speculated in 1702. Thomson used data published by Regnault to calibrate his scale against established measurements.

Thomson critiqued Carnot's original publication and read his analysis to the Royal Society of Edinburgh in January 1849, still convinced that the theory was fundamentally sound. However, though Thomson conducted no new experiments, over the next two years he became increasingly dissatisfied with Carnot's theory and convinced of Joule's. In February 1851 he sat down to articulate his new thinking. However, he was uncertain of how to frame his theory and the paper went through several drafts before he settled on an attempt to reconcile Carnot and Joule. During his rewriting, he seems to have considered ideas that would subsequently give rise to the second law of thermodynamics. In Carnot's theory, lost heat was absolutely lost but Thomson contended that it was “lost to man irrecoverably; but not lost in the material world”. Thomson went on to state a form of the second law:It is impossible, by means of inanimate material agency, to derive mechanical effect from any portion of matter by cooling it below the temperature of the coldest of the surrounding objects.

James Clerk Maxwell

In 1864 James Clerk Maxwell took all the pieces of the electricity and magnetism puzzle and put them together. His mathematical laws of electromagnetism are known as Maxwell’s equations:

· Electricity and magnetism are two different aspects of the same force.

· Every electrical charge has an electrical field around it. This field attracts opposite charges and repels like charges.

· A moving electrical charge or field generates a magnetic field.

· A moving magnetic field generates an electrical field.

As Maxwell considered his discovery, he realized something else that was very interesting. A charge in an electrical field creates a charge in a magnetic field. But a charge in a magnetic field then creates a charge in an electric field. This process can continue on and on. So a single charge in an electric or magnetic field spreads out very rapidly, creating an electromagnetic wave effect.

Maxwell calculated how quickly this electromagnetic wave would move through space. His results said that it would travel at 300,000 kilometers per second (186,000 miles per second). But that is a well-known speed. It is the speed of light. Could it be that light is a form of electromagnetic energy?

Yes. Maxwell discovered that light is an electromagnetic wave. More recent discoveries have shown that light radiation is actually generated by the rapid vibration of electrons in atoms. And it wasn’t long after Maxwell’s laws were published that other new forms of electromagnetic radiation were discovered.

In 1889 Heinrich Hertz discovered the existence of radio waves. These are electromagnetic waves with much longer wavelengths than visible light. In 1895 Wilhelm Roentgen discovered X rays.

In 1897 J. J. Thomson discovered the existence of a negatively charged particle smaller than an atom. This particle became known as the electron. Scientists realized that it is the motion of electrons that carries electrical energy.

Lodygin

The creation of the first incandescent lamp is closely connected with the name of the well-known Russian scientist and inventor, Alexander Nicolayevitch Lodygin.

Lodygin created the first incandescent lamp and laid the foundation for the production of the present-day incandescent lamps that are much more economical than the lamps with carbon electrodes. Lodygin was the first to turn a laboratory device into a means of electric lighting. He was also the first inventor to discover the advantages of the metal wire filaments in comparison with other filaments.

Lodygin’s great achievements paved the way for further successful work of a number of other Russian electrical engineers.

He was born in Tambov region on October 18, 1847. His parents gave him a military education as they wanted him to join the army. However, military service did not interest him at all. So, he resigned soon and devoted all his time to the study of engineering and the solving of technical problems.

In 1872 Lodygin constructed a number of incandescent lamps, these first lamps consisting of a glass bulb with a carbon rod serving as a filament.

In 1873 he produced an improved lamp having two carbon electrodes instead of a one and a longer life (about 2 hours and even 2 hours and a half). That very year Lodygin demonstrated his invention in several Petersburg streets, lighting them by means of his electric lamps. It was the first practical application of the incandescent lamp for lighting purposes. Lots of people went out into the street to see electric light for the first time in their life and, as a matter of fact, for the first time in the world.

Lodygin was never satisfied with his achievements and continued to perfect his invention. Indeed, a more perfect lamp designed by him appeared in 1875. the interest in Lodygin’s lamp greatly increased. However, under very hard economic conditions existing in tsarist Russia he got neither the help nor the necessary support to realize his plans. He himself was practically without money, having spent all he had on his numerous experiments.

Lodygin’s study of metal filaments having a high melting point is a work of world importance. It is he who introduced tungsten filaments in a vacuum. He received a patent for his invention in America. Tungsten is still considered to be very metal that should be used for filament production. The electric lamps that light your room doubtless have tungsten filaments.

Lodygin died on the 16^th of March, 1923, at the age of 76. Death carried away a great Russian scientist, the first to have used the incandescent lamp as a means of lighting.

Yablochkov

Pavel Nicolayevich Yablochkov was born in Saratov Province, on September 26,1847.

At the age of 12, Yablochkov constructed a special geodetic instrument. That was his first invention.

When 14 years old, the boy was taken by his parents to Petersburg. Having finished school, he entered the Military Engineering College and later the Electrotechnical School for officers. At both these schools he studied mathematics, physics, chemistry, electrical engineering, foreign languages, and other subjects. After graduating, he gave up the lucrative post of a military engineer and continued to perfect his knowledge in electrical engineering.

The practical application of the electric arc for lighting purposes begins with Yablochkov. Before him it had seemed impossible because the carbon rods between which the arc had to be formed burned out too quickly. The carbon electrodes burning out so quickly, the distance between them increased. On the other hand, the distance between the rods increasing, the arc itself went out. All the attempts of solving this problem were quite fruitless. The only man who found a solution to this most difficult problem was Yablochkov. He achieved it by placing the two carbon electrodes parallel to each other instead of placing them end to end as other electricians had done before him. Thus, the candle could burn for about one hour and a half.

On March 23, 1876, Yablochkov received the French patent for his “candle” or “Russian candle” as it was generally called.

Yablochkov’s candle was said to be the most interesting device at the London Exhibition of Physical Instruments in 1876. after that exhibition, his invention was demonstrated many times more at several other world exhibitions in Paris. It attracted general attention.

All newspapers and magazines of the time published articles discussing Yablochkov’s great invention. Reports concerning the candle were made at numerous scientific societies. The practical application of the electric candle spread and Yablochkov’s name became known all over the world.

While working at his candle, Yablochkov was the first to realize the advantages of a transformer. He employed a single-phase a.c. transformer with a broken magnetic system. He was also the first scientist who was fully aware of the advantages of the alternating current system and widely used the a.c. for practical purposes. Before him that kind of current had been employed for laboratory work alone.

Although offered great advantages and profits abroad, he came to Russia in order to organize mass production of the candle in his own fatherland.