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Alternating Current (green curve). The horizontal axis measures time; the vertical, current or voltage.

In alternating current (AC, also ac), the movement of electric charge periodically reverses direction. In direct current (DC, also dc), the flow of electric charge is only in one direction.

The abbreviations AC and DC are often used to mean simply alternating and direct, as when they modify current or voltage.^{[1] [2]}

AC is the form in which electric power is delivered to businesses and residences. The usual waveform of an AC power circuit is a sine wave. In certain applications, different waveforms are used, such as triangular or square waves. Audio and radio signals carried on electrical wires are also examples of alternating current. In these applications, an important goal is often the recovery of information encoded (or modulated) onto the AC signal.

History[link]

City lights viewed in a motion blurred exposure. The AC blinking causes the lines to be dotted rather than continuous.

The first alternator to produce alternating current was a dynamo electric generator based on Michael Faraday's principles constructed by the French instrument maker Hippolyte Pixii in 1832.^[3] Pixii later added a commutator to his device to produce more commonly used direct current. The earliest recorded practical application of alternating current is by Guillaume Duchenne, inventor and developer of electrotherapy. In 1855, he announced that AC was superior to direct current for electrotherapeutic triggering of muscle contractions.^[4]

A power transformer developed by Lucien Gaulard and John Dixon Gibbs was demonstrated in London in 1881, and attracted the interest of Westinghouse. They also exhibited the invention in Turin in 1884, where it was adopted for an electric lighting system. Many of their designs were adapted to the particular laws governing electrical distribution in the UK.^{[citation needed]}

In 1882, 1884, and 1885 Gaulard and Gibbs applied for patents on their transformer; however, these were overturned due to prior arts of Nikola Tesla and actions initiated by Sebastian Ziani de Ferranti.

Ferranti went into this business in 1882 when he set up a shop in London designing various electrical devices. Ferranti believed in the success of alternating current power distribution early on, and was one of the few experts in this system in the UK. In 1887 the London Electric Supply Corporation (LESCo) hired Ferranti for the design of their power station at Deptford. He designed the building, the generating plant and the distribution system. On its completion in 1891 it was the first truly modern power station, supplying high-voltage AC power that was then "stepped down" for consumer use on each street. This basic system remains in use today around the world. Many homes all over the world still have electric meters with the Ferranti AC patent stamped on them.

William Stanley, Jr. designed one of the first practical devices to transfer AC power efficiently between isolated circuits. Using pairs of coils wound on a common iron core, his design, called an induction coil, was an early transformer. The AC power system used today developed rapidly after 1886, and includes key concepts by Nikola Tesla, who subsequently sold his patent to George Westinghouse. Lucien Gaulard, John Dixon Gibbs, Carl Wilhelm Siemens and others contributed subsequently to this field. AC systems overcame the limitations of the direct current system used by Thomas Edison to distribute electricity efficiently over long distances even though Edison attempted to discredit alternating current as too dangerous during the War of Currents.

The first commercial power plant in the United States using three-phase alternating current was at the Mill Creek No. 1 Hydroelectric Plant near Redlands, California, in 1893 designed by Almirian Decker. Decker's design incorporated 10,000-volt three-phase transmission and established the standards for the complete system of generation, transmission and motors used today.

The Ames Hydroelectric Generating Plant (spring of 1891) and the original Niagara Falls Adams Power Plant (August 25, 1895) were among the first AC-powered hydroelectric plants.

The Jaruga Hydroelectric Power Plant in Croatia was set in operation on 28 August 1895. The two generator (42 Hz, 550 kW each) and the transformers were produced and installed by the Hungarian company Ganz. The transmission line from the power plant to the City of Šibenik was 11.5 kilometers (7.1 mi) long on wooden towers, and the municipal distribution grid 3000 V/110 V included six transforming stations.

Alternating current circuit theory developed rapidly in the latter part of the 19th and early 20th century. Notable contributors to the theoretical basis of alternating current calculations include Charles Steinmetz, James Clerk Maxwell, Oliver Heaviside, and many others. Calculations in unbalanced three-phase systems were simplified by the symmetrical components methods discussed by Charles Legeyt Fortescue in 1918.

Transmission, distribution, and domestic power supply[link]

AC voltage may be increased or decreased with a transformer. Use of a higher voltage leads to significantly more efficient transmission of power. The power losses in a conductor are a product of the square of the current and the resistance of the conductor, described by the formula

Failed to parse (Missing texvc executable; please see math/README to configure.): P_{\rm L} = I^2 R \, .

This means that when transmitting a fixed power on a given wire, if the current is doubled, the power loss will be four times greater.

The power transmitted is equal to the product of the current and the voltage (assuming no phase difference); that is,

Failed to parse (Missing texvc executable; please see math/README to configure.): P_{\rm T} = IV \, .

Thus, the same amount of power can be transmitted with a lower current by increasing the voltage. It is therefore advantageous when transmitting large amounts of power to distribute the power with high voltages (often hundreds of kilovolts).

However, high voltages also have disadvantages, the main one being the increased insulation required, and generally increased difficulty in their safe handling. In a power plant, power is generated at a convenient voltage for the design of a generator, and then stepped up to a high voltage for transmission. Near the loads, the transmission voltage is stepped down to the voltages used by equipment. Consumer voltages vary depending on the country and size of load, but generally motors and lighting are built to use up to a few hundred volts between phases.

The utilization voltage delivered to equipment such as lighting and motor loads is standardized, with an allowable range of voltage over which equipment is expected to operate. Standard power utilization voltages and percentage tolerance vary in the different mains power systems found in the world.

Modern high-voltage direct-current (HVDC) electric power transmission systems contrast with the more common alternating-current systems as a means for the efficient bulk transmission of electrical power over long distances. HVDC systems, however, tend to be more expensive and less efficient over shorter distances than transformers.   Transmission with high voltage direct current was not feasible when Edison, Westinghouse and Tesla were designing their power systems, since there was then no way to economically convert AC power to DC and back again at the necessary voltages.

Three-phase electrical generation is very common. The simplest case is three separate coils in the generator stator that are physically offset by an angle of 120° to each other. Three current waveforms are produced that are equal in magnitude and 120° out of phase to each other. If coils are added opposite to these (60° spacing), they generate the same phases with reverse polarity and so can be simply wired together.

In practice, higher "pole orders" are commonly used. For example, a 12-pole machine would have 36 coils (10° spacing). The advantage is that lower speeds can be used. For example, a 2-pole machine running at 3600 rpm and a 12-pole machine running at 600 rpm produce the same frequency. This is much more practical for larger machines.

If the load on a three-phase system is balanced equally among the phases, no current flows through the neutral point. Even in the worst-case unbalanced (linear) load, the neutral current will not exceed the highest of the phase currents. Non-linear loads (e.g., computers) may require an oversized neutral bus and neutral conductor in the upstream distribution panel to handle harmonics. Harmonics can cause neutral conductor current levels to exceed that of one or all phase conductors.

For three-phase at utilization voltages a four-wire system is often used. When stepping down three-phase, a transformer with a Delta (3-wire) primary and a Star (4-wire, center-earthed) secondary is often used so there is no need for a neutral on the supply side.

For smaller customers (just how small varies by country and age of the installation) only a single phase and the neutral or two phases and the neutral are taken to the property. For larger installations all three phases and the neutral are taken to the main distribution panel. From the three-phase main panel, both single and three-phase circuits may lead off.

Three-wire single-phase systems, with a single center-tapped transformer giving two live conductors, is a common distribution scheme for residential and small commercial buildings in North America. This arrangement is sometimes incorrectly referred to as "two phase". A similar method is used for a different reason on construction sites in the UK. Small power tools and lighting are supposed to be supplied by a local center-tapped transformer with a voltage of 55 V between each power conductor and earth. This significantly reduces the risk of electric shock in the event that one of the live conductors becomes exposed through an equipment fault whilst still allowing a reasonable voltage of 110 V between the two conductors for running the tools.

A third wire, called the bond (or earth) wire, is often connected between non-current-carrying metal enclosures and earth ground. This conductor provides protection from electric shock due to accidental contact of circuit conductors with the metal chassis of portable appliances and tools. Bonding all non-current-carrying metal parts into one complete system ensures there is always a low electrical impedance path to ground sufficient to carry any fault current for as long as it takes for the system to clear the fault. This low impedance path allows the maximum amount of fault current, causing the overcurrent protection device (breakers, fuses) to trip or burn out as quickly as possible, bringing the electrical system to a safe state. All bond wires are bonded to ground at the main service panel, as is the Neutral/Identified conductor if present.

AC power supply frequencies[link]

The frequency of the electrical system varies by country; most electric power is generated at either 50 or 60 Hertz. Some countries have a mixture of 50 Hz and 60 Hz supplies, notably Japan.

A low frequency eases the design of electric motors, particularly for hoisting, crushing and rolling applications, and commutator-type traction motors for applications such as railways. However, low frequency also causes noticeable flicker in arc lamps and incandescent light bulbs. The use of lower frequencies also provided the advantage of lower impedance losses, which are proportional to frequency. The original Niagara Falls generators were built to produce 25 Hz power, as a compromise between low frequency for traction and heavy induction motors, while still allowing incandescent lighting to operate (although with noticeable flicker). Most of the 25 Hz residential and commercial customers for Niagara Falls power were converted to 60 Hz by the late 1950s, although some^[which?] 25 Hz industrial customers still existed as of the start of the 21st century. 16.7 Hz power (formerly 16 2/3 Hz) is still used in some European rail systems, such as in Austria, Germany, Norway, Sweden and Switzerland.

Off-shore, military, textile industry, marine, computer mainframe, aircraft, and spacecraft applications sometimes use 400 Hz, for benefits of reduced weight of apparatus or higher motor speeds.

Effects at high frequencies[link]

A direct current flows uniformly throughout the cross-section of a uniform wire. An alternating current of any frequency is forced away from the wire's center, toward its outer surface. This is because the acceleration of an electric charge in an alternating current produces waves of electromagnetic radiation that cancel the propagation of electricity toward the center of materials with high conductivity. This phenomenon is called skin effect.

At very high frequencies the current no longer flows in the wire, but effectively flows on the surface of the wire, within a thickness of a few skin depths. The skin depth is the thickness at which the current density is reduced by 63%. Even at relatively low frequencies used for power transmission (50–60 Hz), non-uniform distribution of current still occurs in sufficiently thick conductors. For example, the skin depth of a copper conductor is approximately 8.57 mm at 60 Hz, so high current conductors are usually hollow to reduce their mass and cost.

Since the current tends to flow in the periphery of conductors, the effective cross-section of the conductor is reduced. This increases the effective AC resistance of the conductor, since resistance is inversely proportional to the cross-sectional area. The AC resistance often is many times higher than the DC resistance, causing a much higher energy loss due to ohmic heating (also called I²R loss).

Techniques for reducing AC resistance[link]

For low to medium frequencies, conductors can be divided into stranded wires, each insulated from one other, and the relative positions of individual strands specially arranged within the conductor bundle. Wire constructed using this technique is called Litz wire. This measure helps to partially mitigate skin effect by forcing more equal current throughout the total cross section of the stranded conductors. Litz wire is used for making high-Q inductors, reducing losses in flexible conductors carrying very high currents at lower frequencies, and in the windings of devices carrying higher radio frequency current (up to hundreds of kilohertz), such as switch-mode power supplies and radio frequency transformers.

Techniques for reducing radiation loss[link]

As written above, an alternating current is made of electric charge under periodic acceleration, which causes radiation of electromagnetic waves. Energy that is radiated is lost. Depending on the frequency, different techniques are used to minimize the loss due to radiation.

Twisted pairs[link]

At frequencies up to about 1 GHz, pairs of wires are twisted together in a cable, forming a twisted pair. This reduces losses from electromagnetic radiation and inductive coupling. A twisted pair must be used with a balanced signalling system, so that the two wires carry equal but opposite currents. Each wire in a twisted pair radiates a signal, but it is effectively cancelled by radiation from the other wire, resulting in almost no radiation loss.

Coaxial cables[link]

Coaxial cables are commonly used at audio frequencies and above for convenience. A coaxial cable has a conductive wire inside a conductive tube, separated by a dielectric layer. The current flowing on the inner conductor is equal and opposite to the current flowing on the inner surface of the tube. The electromagnetic field is thus completely contained within the tube, and (ideally) no energy is lost to radiation or coupling outside the tube. Coaxial cables have acceptably small losses for frequencies up to about 5 GHz. For microwave frequencies greater than 5 GHz, the losses (due mainly to the electrical resistance of the central conductor) become too large, making waveguides a more efficient medium for transmitting energy. Coaxial cables with an air rather than solid dielectric are preferred as they transmit power with lower loss.

Waveguides[link]

Waveguides are similar to coax cables, as both consist of tubes, with the biggest difference being that the waveguide has no inner conductor. Waveguides can have any arbitrary cross section, but rectangular cross sections are the most common. Because waveguides do not have an inner conductor to carry a return current, waveguides cannot deliver energy by means of an electric current, but rather by means of a guided electromagnetic field. Although surface currents do flow on the inner walls of the waveguides, those surface currents do not carry power. Power is carried by the guided electromagnetic fields. The surface currents are set up by the guided electromagnetic fields and have the effect of keeping the fields inside the waveguide and preventing leakage of the fields to the space outside the waveguide.

Waveguides have dimensions comparable to the wavelength of the alternating current to be transmitted, so they are only feasible at microwave frequencies. In addition to this mechanical feasibility, electrical resistance of the non-ideal metals forming the walls of the waveguide cause dissipation of power (surface currents flowing on lossy conductors dissipate power). At higher frequencies, the power lost to this dissipation becomes unacceptably large.

Fiber optics[link]

At frequencies greater than 200 GHz, waveguide dimensions become impractically small, and the ohmic losses in the waveguide walls become large. Instead, fiber optics, which are a form of dielectric waveguides, can be used. For such frequencies, the concepts of voltages and currents are no longer used.

Mathematics of AC voltages[link]

A sine wave, over one cycle (360°). The dashed line represents the root mean square (RMS) value at about 0.707

Alternating currents are accompanied (or caused) by alternating voltages. An AC voltage v can be described mathematically as a function of time by the following equation:

Failed to parse (Missing texvc executable; please see math/README to configure.): v(t)=V_\mathrm{peak}\cdot\sin(\omega t)

,

where

• Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle V_{\rm peak}

is the peak voltage (unit: volt),

• Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle\omega

is the angular frequency (unit: radians per second)

• • The angular frequency is related to the physical frequency, Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle f

(unit = hertz), which represents the number of cycles per second, by the equation Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle\omega = 2\pi f

.

• Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle t

is the time (unit: second).

The peak-to-peak value of an AC voltage is defined as the difference between its positive peak and its negative peak. Since the maximum value of Failed to parse (Missing texvc executable; please see math/README to configure.): \sin(x)

is +1 and the minimum value is −1, an AC voltage swings between Failed to parse (Missing texvc executable; please see math/README to configure.): +V_{\rm peak}
and Failed to parse (Missing texvc executable; please see math/README to configure.): -V_{\rm peak}

. The peak-to-peak voltage, usually written as Failed to parse (Missing texvc executable; please see math/README to configure.): V_{\rm pp}

or Failed to parse (Missing texvc executable; please see math/README to configure.): V_{\rm P-P}

, is therefore Failed to parse (Missing texvc executable; please see math/README to configure.): V_{\rm peak} - (-V_{\rm peak}) = 2 V_{\rm peak} .

Power and root mean square[link]

The relationship between voltage and the power delivered is

Failed to parse (Missing texvc executable; please see math/README to configure.): p(t) = \frac{v^2(t)}{R}

where Failed to parse (Missing texvc executable; please see math/README to configure.): R
represents a load resistance.

Rather than using instantaneous power, Failed to parse (Missing texvc executable; please see math/README to configure.): p(t) , it is more practical to use a time averaged power (where the averaging is performed over any integer number of cycles). Therefore, AC voltage is often expressed as a root mean square (RMS) value, written as Failed to parse (Missing texvc executable; please see math/README to configure.): V_{\rm rms} , because

Failed to parse (Missing texvc executable; please see math/README to configure.): P_{\rm time~averaged} = \frac{{V^2}_{\rm rms}}{R}.

For a sinusoidal voltage:

Failed to parse (Missing texvc executable; please see math/README to configure.): V_\mathrm{rms}=\frac{V_\mathrm{peak}}{\sqrt{2}}.

The factor Failed to parse (Missing texvc executable; please see math/README to configure.): \sqrt{2}

is called the crest factor, which varies for different waveforms.

• For a triangle waveform centered about zero

Failed to parse (Missing texvc executable; please see math/README to configure.): V_\mathrm{rms}=\frac{V_\mathrm{peak}}{\sqrt{3}}.

• For a square waveform centered about zero

Failed to parse (Missing texvc executable; please see math/README to configure.): \displaystyle V_\mathrm{rms}=V_\mathrm{peak}.

• For an arbitrary periodic waveform Failed to parse (Missing texvc executable; please see math/README to configure.): v(t)

of period Failed to parse (Missing texvc executable; please see math/README to configure.): T

Failed to parse (Missing texvc executable; please see math/README to configure.): V_\mathrm{rms}=\sqrt{\frac{1}{T} \int_0^{T}{v^2(t) dt}}.

Example[link]

To illustrate these concepts, consider a 230 V AC mains supply used in many countries around the world. It is so called because its root mean square value is 230 V. This means that the time-averaged power delivered is equivalent to the power delivered by a DC voltage of 230 V. To determine the peak voltage (amplitude), we can rearrange the above equation to:

Failed to parse (Missing texvc executable; please see math/README to configure.): V_\mathrm{peak}=\sqrt{2}\ V_\mathrm{rms}.

For our 230 V AC, the peak voltage Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle V_\mathrm{peak}

is therefore Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle 230 V \times\sqrt{2}

, which is about 325 V. The peak-to-peak value Failed to parse (Missing texvc executable; please see math/README to configure.): \scriptstyle V_\mathrm{P-P}

of the 230 V AC is double that, at about 650 V.

See also[link]

	Electronics portal
	Energy portal

References[link]

Further reading[link]

• Willam A. Meyers, History and Reflections on the Way Things Were: Mill Creek Power Plant - Making History with AC, IEEE Power Engineering Review, February 1997, Pages 22–24

External links[link]

• "Alternating Current: Alternating Current". Interactive Java tutorial explaining alternating current. (National High Magnetic Field Laboratory)
• "AC/DC: What's the Difference?". Edison's Miracle of Light, American Experience. (PBS)
• "AC/DC: Inside the AC Generator". Edison's Miracle of Light, American Experience. (PBS)
• Kuphaldt, Tony R., "Lessons In Electric Circuits : Volume II - AC". March 8, 2003. (Design Science License)
• Nave, C. R., "Alternating Current Circuits Concepts". HyperPhysics.
• "Alternating Current (AC)". Magnetic Particle Inspection, Nondestructive Testing Encyclopedia.
• "Alternating current". Analog Process Control Services.
• Hiob, Eric, "An Application of Trigonometry and Vectors to Alternating Current". British Columbia Institute of Technology, 2004.
• "Introduction to alternating current and transformers". Integrated Publishing.
• "Wind Energy Reference Manual Part 4: Electricity". Danish Wind Industry Association, 2003.
• Chan. Keelin, "Alternating current Tools". JC Physics, 2002.
• Williams, Trip "Kingpin", "Understanding Alternating Current, Some more power concepts".
• "Table of Voltage, Frequency, TV Broadcasting system, Radio Broadcasting, by Country".
• Professor Mark Csele's tour of the 25 Hz Rankine generating station
• 50/60 hertz information
• AC circuits Animations and explanations of vector (phasor) representation of RLC circuits
• Blalock, Thomas J., "The Frequency Changer Era: Interconnecting Systems of Varying Cycles". The history of various frequencies and interconversion schemes in the US at the beginning of the 20th century
• (Italian) Generating an a.c voltage.Interactive.

Nikola Tesla
Tesla, aged 37, 1893, photo by Napoleon Sarony
Born	(1856-07-10)10 July 1856 Smiljan, Austrian Empire (Croatian Military Frontier)
Died	7 January 1943(1943-01-07) (aged 86) Manhattan, New York, USA
Residence	Manhattan, New York, USA Karlovac, Croatia Budapest, Hungary
Citizenship	Austrian Empire (10 July 1856 – 29 October 1918)[citation needed] United States (30 July 1891 – 7 January 1943)
Fields	Electrical engineering Mechanical engineering
Institutions	Edison Machine Works Tesla Electric Light & Manufacturing Westinghouse Electric & Manufacturing Co.
Alma mater	Graz University of Technology Charles University in Prague
Known for	Alternating current Bifilar coil Death ray Electrogravitics Induction motor Particle beam weapon Rotating magnetic field Teleforce Tesla coil Tesla electric car Tesla principle Tesla turbine Tesla's Egg of Columbus Tesla's oscillator Telegeodynamics Terrestrial stationary waves Wireless technology
Influences	Ernst Mach
Influenced	Gano Dunn
Notable awards	Order of St. Sava (1892) Elliott Cresson Medal (1894) Edison Medal (1916) John Scott Medal (1934)
Signature

Nikola Tesla (Serbian Cyrillic: Никола Тесла; 10 July 1856 – 7 January 1943) was a Serbian-American inventor, physicist, mechanical engineer, electrical engineer, and futurist. He was an important contributor to the use of commercial electricity, and is best known for developing the modern alternating current (AC) electrical supply system. His many revolutionary developments in the field of electromagnetism in the late 19th and early 20th centuries were based on the theories of electromagnetic technology discovered by Michael Faraday. Tesla's patents and theoretical work also formed the basis of wireless communication and the radio.

Born in the village of Smiljan (now part of Gospić, present day Croatia), Tesla was a subject of the Austrian Empire by birth and later became an American citizen.^[1] Because of his 1894 demonstration of short range wireless communication through radio^[2] and as the eventual victor in the "War of Currents", he was widely respected as one of the greatest electrical engineers who worked in America.^[3] 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.^[4] Tesla demonstrated wireless energy transfer to power electronic devices in 1891,^[5] and aspired to intercontinental wireless transmission of industrial power in his unfinished Wardenclyffe Tower project.

Tesla became reclusive towards the end of his life, living alone in a New York City hotel room and only appearing occasionally to make unusual statements to the press.^[6][7] Because of his pronouncements and the nature of his work over the years Tesla gained a reputation in popular culture as the archetypal "mad scientist".^[8][9] He died with little money to his name.^[10]

Tesla's work fell into relative obscurity after his death but since the 1990s his reputation has experienced a popular culture comeback.^[11] In 2005 he was listed amongst the top 100 nominees in the TV show "The Greatest American", an open access popularity poll conducted by AOL and The Discovery Channel.

The SI unit measuring magnetic field B (also referred to as the magnetic flux density and magnetic induction), the tesla, was named in his honor (at the CGPM, Paris, 1960).

Early years[link]

Nikola Tesla was born to Serbian parents in the village of Smiljan, Austrian Empire near the town of Gospić, in the territory of modern-day Croatia. His baptismal certificate reports that he was born on 28 June (N.S. 10 July) 1856 to father Milutin Tesla, a priest in the Serbian Orthodox Church.^[12] His mother was Đuka Tesla, née Mandić, whose father was also a Serbian Orthodox priest.^[13] She was talented in making home craft tools and memorized many Serbian epic poems, but never learned to read.^[14] Tesla's biographer John O'Neill relates that "the Tesla and Mandić families originally came from the western part of Serbia near Montenegro."^[15]

Nikola was the fourth of five children, having one older brother (Danilo, who was killed in a horse-riding accident when Nikola was five) and three sisters (Milka, Angelina and Marica).^[16] His family moved to Gospić in 1862. Tesla attended school at Higher Real Gymnasium in Karlovac.^[17] He finished a four-year term in the span of three years.^[18]

Nikola Tesla's house (parish hall) in village Smiljan where he was born and the church where his father served (present day Croatia).

Tesla went on to study electrical engineering at the Austrian Polytechnic in Graz (1875). While there, he studied the uses of alternating current. Some sources say he received Baccalaureate degrees from the university at Graz.^[19][20][21] However, the university says that he did not receive a degree and did not continue beyond the first semester of his third year, during which he stopped attending lectures.^{[22][23][24][25]} In December 1878, Tesla left Graz and broke all relations with his family. His friends thought that he had drowned in the Mur River. He went to Marburg, (today's Maribor, in Slovenia), where he was first employed as an assistant engineer for a year. He suffered a nervous breakdown during this time. Tesla was later persuaded by his father to attend the Charles-Ferdinand University in Prague, which he attended for the summer term of 1880. Here, he was influenced by Ernst Mach. However, after his father died, he left the university, having completed only one term.^[26]

Nikola Tesla c. 1879 at age 23, and his passport from 1883

Tesla engaged in reading many works, memorizing complete books, supposedly having a photographic memory.^[27] Tesla related in his autobiography that he experienced detailed moments of inspiration. During his early life, Tesla was stricken with illness time and time again. He suffered a peculiar affliction in which blinding flashes of light would appear before his eyes, often accompanied by visions. Much of the time the visions were linked to a word or idea he might have come across, at other times they would provide the solution to a particular problem he had been encountering; just by hearing the name of an item, he would be able to envision it in realistic detail. Modern-day synesthetes report similar symptoms. Tesla would visualize an invention in his mind with extreme precision, including all dimensions, before moving to the construction stage; a technique sometimes known as picture thinking. He typically did not make drawings by hand, instead just conceiving all ideas with his mind. Tesla also often had flashbacks to events that had happened previously in his life; these began during his childhood.^[27]

In 1880, he moved to Budapest to work under Tivadar Puskás in a telegraph company,^[28] the National Telephone Company. There, he met Nebojša Petrović, a young, Serbian inventor who lived in Austria. Although their encounter was brief, they did work on a project together using twin turbines to create continual power. On the opening of the telephone exchange in Budapest, 1881, Tesla became the chief electrician to the company, and was later engineer for the country's first telephone system. He also developed a device that, according to some, was a telephone repeater or amplifier, but according to others could have been the first loudspeaker.^[29]

Drawing from U.S. Patent 381968, illustrating principle of Tesla's alternating current motor

Working for Edison in France and the U.S[link]

In 1882 he moved to Paris, to work as an engineer for the Continental Edison Company, designing improvements to electric equipment brought overseas from Edison's ideas. According to Tesla's autobiography, in the same year he conceived of his induction motor and began developing various devices that use rotating magnetic fields for which he received patents in 1888. The paternity of the invention remains controversial since a prototype induction motor was demonstrated in Europe in 1885 by Galileo Ferraris.^{[30][31][32][33]} Ferraris published his findings in 1888.

On 6 June 1884, Tesla first arrived in the United States, in New York City^[34] with little besides a letter of recommendation from Charles Batchelor, a former employer. In the letter of recommendation to Thomas Edison, it is claimed that Batchelor wrote, 'I know two great men and you are one of them; the other is this young man', but the exact contents of the letter is disputed in McNichol's book. Edison hired Tesla to work for his Edison Machine Works. Tesla's work for Edison began with simple electrical engineering and quickly progressed to solving some of the company's most difficult problems. Tesla was even offered the task of completely redesigning the Edison company's direct current generators.^[35]

In 1885 Tesla claimed he could redesign Edison's inefficient motor and generators, making an improvement in both service and economy. According to Tesla, Edison remarked "There's fifty thousand dollars in it for you - if you can do it".^[36] This has been noted as an odd statement from an Edison whose company was stingy with pay and did not have that sort of cash on hand.^[37] After months of work when Tesla finished the task and inquired about payment Edison claimed he was only joking replying, "Tesla, you don't understand our American humor".^[38][39] Edison offered a $10 a week raise over Tesla's US$18 per week salary, but Tesla refused it and immediately resigned.^[36]

Tesla, in need of work, eventually found himself digging ditches for a short period of time for the Edison company. He used this time to focus on his AC polyphase system.^[40]

Middle years[link]

Wireless transmission of power and energy demonstration during his high frequency and potential lecture of 1891 Electromechanical devices and principles developed by Nikola Tesla: Various devices that use rotating magnetic fields (1882) The Induction motor, rotary transformers, and "high" frequency alternators The Tesla coil,[41] his magnifying transmitter, and other means for increasing the intensity of electrical oscillations (including condenser discharge transformations and the Tesla oscillators[42][43]) Alternating current long-distance electrical transmission system[44] (1888) and other methods and devices for power transmission Systems for wireless communication (prior art for the invention of radio) and radio frequency oscillators[45] Robotics and the electronic logic gate[46] Electrotherapy Tesla currents[47][48][49] Wireless transfer of electricity and the Tesla effect[50][51] Tesla impedance phenonomena[52] Tesla electro-static field Tesla principle Bifilar coil Telegeodynamics Tesla insulation Tesla impulses[53] Tesla frequencies[41] Tesla discharge[41] Forms of commutators and methods of regulating third brushes Tesla turbines (e.g., bladeless turbines) for water, steam and gas and the Tesla pumps Tesla igniter Corona discharge ozone generator Tesla compressor X-rays Tubes using the Bremsstrahlung process Devices for ionized gases and "Hot Saint Elmo's Fire".[54] Devices for high field emission Devices for charged particle beams Phantom streaming devices[55] Arc light systems Methods for providing extremely low level of resistance to the passage of electric current (predecessor to superconductivity) Voltage multiplication circuitry Devices for high voltage discharges Devices for lightning protection VTOL aircraft Dynamic theory of gravity Concepts for electric vehicles Polyphase systems

In 1886, Tesla formed his own company, Tesla Electric Light & Manufacturing. The initial financial investors disagreed with Tesla on his plan for an alternating current motor and eventually relieved him of his duties at the company. Tesla worked in New York as a laborer from 1886 to 1887 to feed himself and raise capital for his next project. In 1887, he constructed a brushless alternating current induction motor, which he demonstrated to the American Institute of Electrical Engineers (now IEEE) in 1888. In the same year, he developed the principles of his Tesla coil, and began working with George Westinghouse at Westinghouse Electric & Manufacturing Company's Pittsburgh labs. Westinghouse listened to his ideas for polyphase systems which would allow transmission of alternating current electricity over long distances.

In April 1887, Tesla began investigating what would later be called X-rays using his own single terminal vacuum tubes (similar to his patent #514,170). This device differed from other early X-ray tubes in that it had no target electrode. The modern term for the phenomenon produced by this device is bremsstrahlung (or braking radiation). It is now known 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. He also used Geissler tubes. By 1892, Tesla became aware of the skin damage that Wilhelm Röntgen later identified as an effect of X rays.

In the early research, Tesla devised several experimental setups to produce X-rays. Tesla held that, with his circuits, the "instrument will [... enable one to] generate Roentgen rays of much greater power than obtainable with ordinary apparatus".^[56]

He also commented on the hazards of working with his circuit and single-node X-ray-producing devices. Of his many notes in the early investigation of this phenomenon, he attributed the skin damage to various causes. He believed early on that damage to the skin was not caused by the Roentgen rays, but the ozone generated in contact with the skin, and to a lesser extent, nitrous acid. Tesla incorrectly held that x-rays were longitudinal waves, such as those produced in waves in plasma. There are known examples of this and these plasma waves can occur in the situation of force-free magnetic fields.^[57][58] His hypotheses and experiments were confirmed by others.^[59]

Tesla continued research in the field. He performed several experiments prior to Roentgen's discovery (including photographing the bones of his hand; later, he sent these images to Roentgen) but did not make his findings widely known; much of his research was lost in the 5th Avenue laboratory fire of March 1895.

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).^[50][60]

American citizenship[link]

Tesla demonstrated a radio-controlled boat on 1898 U.S. Patent 613,809, named Method of an Apparatus for Controlling Mechanism of Moving Vehicle or Vehicles

On 30 July 1891, at the age of 35, he became a naturalized citizen of the United States. Tesla established his South Fifth Avenue laboratory in New York in the same year. Later, Tesla established his Houston Street laboratory in New York at 46 E. Houston Street. He lit electric lamps wirelessly at both of the New York locations, providing evidence for the potential of wireless power transmission.^[61]

Soon thereafter, in 1892,^[62] Tesla was awakened from a dream in which his mother had died.^[63] He returned to Europe for her funeral. After her death, Tesla fell ill. He spent two to three weeks recuperating in Gospić and the village of Tomingaj near Gračac, his mother's birthplace.

Some of Tesla's closest friends were artists. He befriended Century Magazine editor Robert Underwood Johnson, who adapted several Serbian poems of Jovan Jovanović Zmaj (which Tesla translated). Also during this time, Tesla was influenced by the Vedic philosophy (i.e., Hinduism) teachings of the Swami Vivekananda; so much so that, after his exposure to Hindu-Vedic thought, Tesla started using Sanskrit words to name some of his fundamental concepts regarding matter and energy.^[64]

Nikola Tesla's AC dynamo-electric machine (Electric generator) used to generate AC which is used to transport electricity across great distances. It is contained in U.S. Patent 390,721.

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. Tesla served, from 1892 to 1894, as the vice president of the American Institute of Electrical Engineers, the forerunner (along with the Institute of Radio Engineers) of the modern-day IEEE. 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, invented a cordless gas discharge lamp, and transmitted electromagnetic energy without wires, building the first radio transmitter.^{[citation needed]} In St. Louis, Missouri, Tesla made a demonstration related to radio communication in 1893.^{[citation needed]} Addressing the Franklin Institute in Philadelphia, Pennsylvania and the National Electric Light Association, he described and demonstrated in detail its principles. Tesla's demonstrations were written about widely through various media outlets. Tesla also investigated harvesting energy that is present throughout space. He believed that it was merely a question of time when men would succeed in attaching their machinery to the very wheelwork of nature, stating: "Ere many generations pass, our machinery will be driven by a power obtainable at any point of the universe."^[65]

At the 1893 World's Fair, the World's Columbian Exposition in Chicago, an international exposition was held which, for the first time, devoted a building to electrical exhibits. It was a historic event as Tesla and George Westinghouse introduced visitors to AC power by using it to illuminate the Exposition. On display were fluorescent lamps developed by Westinghouse^[66] and single node bulbs. An observer noted:

Within the room was suspended two hard-rubber plates covered with tin foil. These were about fifteen feet apart, and served as terminals of the wires leading from the transformers. When the current was turned on, the lamps or tubes, which had no wires connected to them, but lay on a table between the suspended plates, or which might be held in the hand in almost any part of the room, were made luminous. These were the same experiments and the same apparatus shown by Tesla in London about two years previous, "where they produced so much wonder and astonishment".^[67]

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'.^[68] Just before Tesla's completion of his work and the filing of a patent application, Tesla's laboratory burned down, destroying all his equipment, models and inventions. Immediately after the fire, Carl von Linde, in Germany, filed a patent application for the same process.^[69]

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.^{[citation needed]} The same concept is used in virtual lightning rods and the electrolaser electroshock weapon,^[70] and has been proposed for disabling vehicles.

Also in the late 1880s, Tesla and Thomas Edison became adversaries in part because of Edison's promotion of direct current (DC) for electric power distribution over the more efficient alternating current advocated by Tesla and Westinghouse. Until the development of the induction motor, AC's advantages for long distance high voltage transmission were counterbalanced by the inability to operate motors on AC.^{[citation needed]} As a result of the "War of Currents", Edison and Westinghouse went nearly bankrupt, so in 1897, Tesla released Westinghouse from contract, providing Westinghouse a break from Tesla's patent royalties. Also in 1897, Tesla researched radiation, which led to setting up the basic formulation of cosmic rays.^[71]

In 1897, at age 41, Tesla filed the first radio patent (U.S. Patent 645,576). A year later, he demonstrated a radio-controlled boat to the US military, believing that the military would want things such as radio-controlled torpedoes. Tesla claimed to have developed the "Art of Telautomatics", a form of robotics, as well as the technology of remote control.^[72] In 1898, he demonstrated a radio-controlled boat to the public during an electrical exhibition at Madison Square Garden. Tesla called his boat a "teleautomaton".^[73] In the same year, Tesla devised an "electric igniter" or spark plug for Internal combustion gasoline engines. He gained U.S. Patent 609,250, "Electrical Igniter for Gas Engines", on this mechanical ignition system. Tesla lived in the former Gerlach Hotel, renamed The Radio Wave building, at 49 W 27th St. (between Broadway and Sixth Avenue), Lower Manhattan, before the end of the century where he conducted the radio wave experiments. A commemorative plaque was placed on the building in 1977 to honor his work. Remote radio control remained a novelty until World War I and afterward, when a number of countries used it in military programs.

Colorado Springs[link]

Publicity picture of Nikola Tesla sitting in his laboratory in Colorado Springs with his "Magnifying transmitter" generating millions of volts. The arcs are about 7 meters (23 ft) long. (Tesla's notes identify this as a multiple exposure photograph.)

An experiment in Colorado Springs. This bank of lights is receiving power by means of electrodynamic induction from a nearby transmitter

A Colorado Springs experiment: here a grounded tuned coil in resonance with a distant transmitter illuminates a light near the bottom of the picture.

In 1899, Tesla decided to move and began research in Colorado Springs, Colorado in a lab located near Foote Ave. and Kiowa St.,^[74] where he would have room for his high-voltage, high-frequency experiments. Upon his arrival he told reporters that he was conducting wireless telegraphy experiments transmitting signals from Pikes Peak to Paris. Tesla's diary contains explanations of his experiments concerning the ionosphere and the ground's telluric currents via transverse waves and longitudinal waves.^[75] 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).^[76] Tesla also investigated atmospheric electricity, observing lightning signals via his receivers. Reproductions of Tesla's receivers and coherer circuits show an unpredicted level of complexity (e.g., distributed high-Q helical resonators, radio frequency feedback, crude heterodyne effects, and regeneration techniques).^[77] Tesla stated that he observed stationary waves during this time.^[78]

Tesla researched ways to transmit power and energy wirelessly over long distances (via transverse waves, to a lesser extent, and, more readily, longitudinal waves). He transmitted extremely low frequencies through the ground as well as between the Earth's surface and the Kennelly–Heaviside layer. He received patents on wireless transceivers that developed standing waves by this method. In his experiments, he made mathematical calculations and computations based on his experiments and discovered that the resonant frequency of the Earth was approximately 8 hertz (Hz). In the 1950s, researchers confirmed that the resonant frequency of the Earth's ionospheric cavity was in this range (later named the Schumann resonance).

In Colorado Springs Tesla carried out various long distance wireless transmission-reception experiments. Tesla effect is the application of a type of electrical conduction (that is, the movement of energy through space and matter; not just the production of voltage across a conductor). Through longitudinal waves,^{[citation needed]} Tesla transferred energy to receiving devices. He sent electrostatic forces through natural media across a conductor situated in the changing magnetic flux and transferred electrical energy to a wireless receiver.

In the Colorado Springs lab, Tesla observed unusual signals that he later thought may have been evidence of extraterrestrial radio wave communications coming from Venus or Mars.^[79] He noticed repetitive signals from his receiver which were substantially different from the signals he had noted from storms and earth noise. Specifically, he later recalled that the signals appeared in groups of one, two, three, and four clicks together. Tesla had mentioned that he thought his inventions could be used to talk with other planets. There have even been claims that he invented a "Teslascope" for just such a purpose. It is debatable what type of signals Tesla received or whether he picked up anything at all. Research has suggested that Tesla may have had a misunderstanding of the new technology he was working with,^[80] or that the signals Tesla observed may have been non-terrestrial natural radio source such as the Jovian plasma torus signals.^[81]

Tesla left Colorado Springs on 7 January 1900. The lab was torn down ca. 1905 and its contents sold to pay debts. The Colorado experiments prepared Tesla for the establishment of the trans-Atlantic wireless telecommunications facility known as Wardenclyffe near Shoreham, Long Island.

Wardenclyffe years[link]

In 1900, with US$150,000 (51% from J. Pierpont Morgan), Tesla began planning the Wardenclyffe Tower facility. In June 1902, Tesla's lab operations were moved to Wardenclyffe from Houston Street. The tower was dismantled for scrap during World War I.^[82]

On his 50th birthday in 1906, Tesla demonstrated his 200 hp (150 kW) 16,000 rpm bladeless turbine. During 1910–1911 at the Waterside Power Station in New York, several of his bladeless turbine engines were tested at 100–5000 hp.

Nobel prize and Tesla[link]

Since the Nobel Prize in Physics was awarded to Guglielmo Marconi for radio in 1909, Thomas Edison and Tesla were mentioned in a press dispatch as potential laureates to share the Nobel Prize of 1915, leading to one of several Nobel Prize controversies. Some sources have claimed that because of their animosity toward each other neither was given the award, despite their scientific contributions; that each sought to minimize the other's achievements and right to win the award; that both refused ever to accept the award if the other received it first; and that both rejected any possibility of sharing it.^[14][83]

In the years after these rumors, neither Tesla nor Edison won the Prize (although Edison did receive one of 38 possible bids in 1915, and Tesla did receive one bid out of 38 in 1937).^[84] Earlier, Tesla alone was rumored to have been nominated for the Nobel Prize of 1912. The rumored nomination was primarily for his experiments with tuned circuits using high-voltage high-frequency resonant transformers.

Later years[link]

In 1915, Tesla filed a lawsuit against Marconi attempting, unsuccessfully, to obtain a court injunction against Marconi's claims. After Wardenclyffe, Tesla built the Telefunken Wireless Station in Sayville, Long Island. Some of what he wanted to achieve at Wardenclyffe was accomplished with the Telefunken Wireless. In 1917, the facility was seized and torn down by the Marines, because it was suspected that it could be used by German spies.

The Wardenclyffe Tower facility

Before World War I (1914-1918), Tesla looked overseas for investors to fund his research. When the war started, Tesla lost the funding he was receiving from his patents in European countries. After the war ended, Tesla made predictions regarding the relevant issues of the post-World War I environment, in a printed article (20 December 1914). Tesla believed that the League of Nations was not a remedy for the times and issues. Tesla started to exhibit pronounced symptoms of obsessive-compulsive disorder in the years following. He became obsessed with the number three; he often felt compelled to walk around a block three times before entering a building, demanded a stack of three folded cloth napkins beside his plate at every meal, etc. The nature of OCD was little understood at the time and no treatments were available, so his symptoms were considered by some to be evidence of partial insanity, and this undoubtedly hurt what was left of his reputation.

At this time, he was staying at The Waldorf-Astoria Hotel, renting in an arrangement for deferred payments. Eventually, the Wardenclyffe deed was turned over to George Boldt, proprietor of the Waldorf-Astoria, to pay a US$20,000 debt. In 1917, around the time that the Wardenclyffe Tower was demolished by Boldt to make the land a more viable real estate asset, Tesla received AIEE's highest honor, the Edison Medal.

Tesla, in August 1917, first established principles regarding frequency and power level for the first primitive radar units.^[85]

In 1934, Émile Girardeau, working with the first French radar systems, stated he was building them "according to the principles stated by Tesla". By the 1920s, Tesla was reportedly negotiating with the United Kingdom government about a ray system.^{[citation needed]} Tesla had also stated that efforts had been made to steal the so called "death ray".^{[citation needed]} It is suggested that the removal of the Chamberlain government ended negotiations.^{[citation needed]}

On Tesla's 75th birthday in 1931, Time magazine put him on its cover. The cover caption noted his contribution to electrical power generation. Tesla received his last patent in 1928 for an apparatus for aerial transportation which was the first instance of VTOL aircraft. By the end of 1931, Tesla released "On Future Motive Power" which covered an ocean thermal energy conversion system. In 1934, Tesla wrote to consul Janković of his homeland. The letter contained a message of gratitude to Mihajlo Pupin who had initiated a donation scheme by which American companies could support Tesla. Tesla refused the assistance, choosing instead to live on a modest pension received from Yugoslavia, and to continue his research.

Tesla's famous telegram exchange with Vladko Maček is preserved in the Technical Museum in Zagreb, Croatia

In 1936, replying to a birthday telegram from Vladko Maček, Tesla said he was "equally proud" of his "Serbian origin and Croatian homeland",^[86] a phrase often paraphrased in conciliatory context at modern-day joint Croatian-Serbian Tesla celebrations.^[87] In addition, in the same telegram, Tesla wrote "Long live all Yugoslavs."^{[citation needed]} When others tried to co-opt him into ethnic and other conflicts in Yugoslavia, Tesla once replied: "If your hate could be turned into electricity, it would light up the whole world."^[86]

Field theories[link]

When he was 81, Tesla stated he had completed a "dynamic theory of gravity".^[88] He stated that it was "worked out in all details" and that he hoped to soon give it to the world.^[89] The theory was never published.

The bulk of the theory was developed between 1892 and 1894, during the period that he was conducting experiments with high frequency and high potential electromagnetism and patenting devices for their use. Reminiscent of Mach's principle, Tesla stated in 1925 that:

Nikola Tesla, with Ruđer Bošković's book Theoria Philosophiae Naturalis, sits in front of the spiral coil of his high-frequency transformer at East Houston Street, New York.

There is no thing endowed with life—from man, who is enslaving the elements, to the nimblest creature—in all this world that does not sway in its turn. Whenever action is born from force, though it be infinitesimal, the cosmic balance is upset and the universal motion results.

Tesla was critical of Einstein's relativity work, calling it:

...[a] magnificent mathematical garb which fascinates, dazzles and makes people blind to the underlying errors. The theory is like a beggar clothed in purple whom ignorant people take for a king ... its exponents are brilliant men but they are metaphysicists rather than scientists ...^[90]

Tesla also argued:

I hold that space cannot be curved, for the simple reason that it can have no properties. It might as well be said that God has properties. He has not, but only attributes and these are of our own making. Of properties we can only speak when dealing with matter filling the space. To say that in the presence of large bodies space becomes curved is equivalent to stating that something can act upon nothing. I, for one, refuse to subscribe to such a view.^[91]

Tesla also believed that much of Albert Einstein's relativity theory had already been proposed by Ruđer Bošković, stating in an unpublished interview:

...the relativity theory, by the way, is much older than its present proponents. It was advanced over 200 years ago by my illustrious countryman Ruđer Bošković, the great philosopher, who, notwithstanding other and multifold obligations, wrote a thousand volumes of excellent literature on a vast variety of subjects. Bošković dealt with relativity, including the so-called time-space continuum ...'.^[92]

Directed-energy weapon[link]

Later in life, Tesla made remarkable claims concerning a "teleforce" weapon.^[93] The press called it a "peace ray" or death ray.^[94][95] In total, the components and methods included:^{[96][97][dubious – discuss]}

• An apparatus for producing manifestations of energy in free air instead of in a high vacuum as in the past. This, according to Tesla in 1934, was accomplished.
• A mechanism for generating tremendous electrical force. This, according to Tesla, was also accomplished.
• A means of intensifying and amplifying the force developed by the second mechanism.
• A new method for producing a tremendous electrical repelling force. This would be the projector, or gun, of the invention.

Tesla worked on plans for a directed-energy weapon from the early 1900s until his death.^{[dubious – discuss]} In 1937, Tesla wrote a treatise entitled "The Art of Projecting Concentrated Non-dispersive Energy through the Natural Media", which concerned charged particle beams.^{[98][dubious – discuss]} Tesla published the document in an attempt to expound on the technical description of a "superweapon that would put an end to all war." This treatise describing the particle beam is currently in the Nikola Tesla Museum archive in Belgrade. 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 (through electrostatic repulsion).^{[98][dubious – discuss]}

His records indicate that the device is based on a narrow stream of atomic clusters of liquid mercury or tungsten accelerated via high voltage (by means akin to his magnifying transformer). Tesla gives the following description concerning the particle gun's operation:

[The nozzle would] send concentrated beams of particles through the free air, of such tremendous energy that they will bring down a fleet of 10,000 enemy airplanes at a distance of 200 miles from a defending nation's border and will cause armies to drop dead in their tracks.^[99]

Tesla described the weapon as being able to be used against ground based infantry or for antiaircraft purposes.^[100] Tesla tried to interest the US War Department in the device.^[101] He also offered this invention to European countries.^[102] None of the governments purchased a contract to build the device. He was unable to act on his plans.^[103]

Theoretical inventions[link]

Another of Tesla's theorized inventions is commonly referred to as Tesla's Flying Machine, which appears to resemble an ion-propelled aircraft.^[104] Tesla claimed that one of his life goals was to create a flying machine that would run without the use of an airplane engine, wings, ailerons, propellers, or an onboard fuel source. Initially, Tesla pondered about the idea of a flying craft that would fly using an electric motor powered by grounded base stations. As time progressed, Tesla suggested that perhaps such an aircraft could be run entirely electro-mechanically. The theorized appearance would typically take the form of a cigar or saucer.^[105]

Personal life[link]

Nikola Tesla's father Milutin, Serbian Orthodox priest in the village of Smiljan.

Possessing an eidetic memory, Nikola Tesla was a polyglot, and along with his native tongue he also spoke Czech, English, French, German, Hungarian, Italian, and Latin.^[106]

During his second year of study at Graumltz, Tesla developed a passion for (and became very proficient at) billiards, chess and card-playing, sometimes spending more than 48 hours in a stretch at a gaming table.^[107][108] Tesla by nature required little sleep, claiming to never sleep more than two hours.^[109] On one occasion at his laboratory Tesla worked for a period of 84 hours without sleep or rest.^[110]

Tesla may have suffered from obsessive-compulsive disorder, and had many unusual quirks and phobias. He did things in threes, and was adamant about staying in a hotel room with a number divisible by three. Tesla was physically revolted by jewelry, notably pearl earrings.^[111] He was fastidious about cleanliness and hygiene, and was by all accounts mysophobic.

Tesla was obsessed with pigeons, ordering special seeds for the pigeons he fed in Central Park and even bringing injured ones into his hotel room to nurse them back to health. Tesla was an animal-lover, often reflecting contentedly about a childhood cat, "The Magnificent Mačak." Tesla never married. He was celibate and claimed that his chastity was very helpful to his scientific abilities.^[27] Nonetheless there have been numerous accounts of women vying for Tesla's affection, even some madly in love with him. Tesla, though polite, behaved rather ambivalently to these women in the romantic sense.

Tesla was prone to alienating himself and was generally soft-spoken. However, when he did engage in a social life, many people spoke very positively and admiringly of him. Robert Underwood Johnson described him as attaining a "distinguished sweetness, sincerity, modesty, refinement, generosity, and force." His loyal secretary, Dorothy Skerrit, wrote: "his genial smile and nobility of bearing always denoted the gentlemanly characteristics that were so ingrained in his soul." Tesla's friend Hawthorne wrote that "seldom did one meet a scientist or engineer who was also a poet, a philosopher, an appreciator of fine music, a linguist, and a connoisseur of food and drink."

Nevertheless, Tesla could be harsh at times; he openly expressed his disgust for overweight people, once firing a secretary because of her weight.^[112] He was quick to criticize others' clothing as well, on several occasions directing a subordinate to go home and change her dress.^[27]

Tesla was widely known for his great showmanship, presenting his innovations and demonstrations to the public as an artform, almost like a magician. This seems to conflict with his observed reclusiveness; Tesla was a complicated figure. He refused to hold conventions without his Tesla coil blasting electricity throughout the room, despite the audience often being terrified, though he assured them everything was perfectly safe.

Mark Twain in Tesla's lab, early 1894

In middle age, Tesla became close friends with Mark Twain. They spent a lot of time together in his lab and elsewhere.

Tesla remained bitter in the aftermath of his dispute with Edison. The day after Edison died the New York Times contained extensive coverage of Edison's life, with the only negative opinion coming from Tesla, who was quoted as saying:

He had no hobby, cared for no sort of amusement of any kind and lived in utter disregard of the most elementary rules of hygiene  ... His method was inefficient in the extreme, for an immense ground had to be covered to get anything at all unless blind chance intervened and, at first, I was almost a sorry witness of his doings, knowing that just a little theory and calculation would have saved him 90 percent of the labor. But he had a veritable contempt for book learning and mathematical knowledge, trusting himself entirely to his inventor's instinct and practical American sense.^[113]

Shortly before he died, Edison said that his biggest mistake had been in trying to develop direct current, rather than the superior alternating current system that Tesla had put within his grasp.^[114]

Tesla was good friends with Robert Underwood Johnson. He had amicable relations with Francis Marion Crawford, Stanford White, Fritz Lowenstein, George Scherff, and Kenneth Swezey. He ripped up a Westinghouse contract that would have made him the world's first billionaire, in part because of the implications it would have on his future vision of free power, and in part because it would run Westinghouse out of business, and Tesla had no desire to deal with the creditors.^{[citation needed]}

Tesla lived the last ten years of his life in a two-room suite on the 33rd floor of the Hotel New Yorker, room 3327. There, near the end of his life, Tesla showed signs of encroaching senility, claiming to be visited by a specific white pigeon daily. Several biographers note that Tesla viewed the death of the pigeon as a "final blow" to himself and his work.

Tesla believed that war could not be avoided until the cause for its recurrence was removed, but was opposed to wars in general. However, Tesla came to find exceptions in which he thought certain situations and wars were justifiable.^[115] Tesla sought to reduce distance, such as in communication for better understanding, transportation, and transmission of energy, as a means to ensure friendly international relations.^[116]

Tesla was a life-long bachelor. Like many of his era, he became a proponent of an imposed selective breeding version of eugenics. His opinions stemmed from a belief that humans already interfered with the natural "ruthless workings of nature", rather than conceptions of a "master race" or inherent superiority of one person over another. His advocacy of it was however to push it further. In a 1937 interview, he stated:

... man's new sense of pity began to interfere with the ruthless workings of nature. The only method compatible with our notions of civilization and the race is to prevent the breeding of the unfit by sterilization and the deliberate guidance of the mating instinct .... The trend of opinion among eugenists is that we must make marriage more difficult. Certainly no one who is not a desirable parent should be permitted to produce progeny. A century from now it will no more occur to a normal person to mate with a person eugenically unfit than to marry a habitual criminal.^[117]

In 1926, Tesla commented on the ills of the social subservience of women and the struggle of women toward gender equality, indicated that humanity's future would be run by "Queen Bees". He believed that women would become the dominant sex in the future.^[118]

In his later years Tesla became a vegetarian. In an article for Century Illustrated Magazine he wrote: "It is certainly preferable to raise vegetables, and I think, therefore, that vegetarianism is a commendable departure from the established barbarous habit." Tesla argued that it is wrong to eat uneconomic meat when large numbers of people are starving; he also believed that plant food was "superior to [meat] in regard to both mechanical and mental performance". He also argued that animal slaughter was "wanton and cruel".^[119]

In his final years he suffered from extreme sensitivity to light, sound and other influences.^[120]

Death[link]

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Gilded urn with Tesla's ashes, in his favorite geometrical object of sphere, Nikola Tesla Museum, Belgrade.

Tesla died on 7 January 1943 at age 86 from heart thrombus, alone in room 3327 of the New Yorker Hotel.^[121] A few days after Tesla's death, the information center of the Yugoslav royal government-in-exile released a statement giving a short review of Tesla's achievements and the schedule for his memorial service and funeral. The speech, written by Louis Adamic, was read in a live broadcast on Radio New York by the mayor of New York City, Fiorello La Guardia, on 10 January 1943. The remains of Nikola Tesla were taken to Campbell cemetery. The protocol anticipated the funeral service would be conducted on 12 January in the Cathedral of Saint John the Divine in Manhattan.^[122] Bishop William T. Manning delivered the introductory and the last prayer in English. The funeral service was conducted in the name of the Serbian Orthodox Church by priest Dusan Sukletovic, the superior of the Church of St. Sava of the New York parish. The bereaved family members present at the funeral were Sava Kosanovic and Nikola Trbojevic. A state funeral was attended by 2000 people. Tesla's casket was draped with U. S. and Yugoslav flags. The pallbearers were Nobel prize winners. Telegrams of condolence were received from many notables including the First Lady of the United States, Mrs Eleanor Roosevelt and Vice-President Henry A. Wallace. Tesla's body was cremated and his ashes taken to Belgrade, Serbia, then-Yugoslavia in 1957. The urn containing his ashes was placed in the Nikola Tesla Museum in Belgrade. Despite having sold his AC electricity patents, Tesla died with significant debts. Later that year the US Supreme Court upheld Tesla's patent number 645576 in a ruling that served as the basis for patented radio technology in the United States.^[123]

Soon after his death Tesla's safe was opened by his nephew Sava Kosanović. Shortly thereafter Tesla's papers and other property were impounded by the United States' Alien Property Custodian office in Tesla's compound at the Manhattan Warehouse, even though he was a naturalized citizen.

Dr. John G. Trump was the main government official who went over Tesla's secret papers after his death in 1943. At the time, Trump was a well-known electrical engineer serving as a technical aide to the National Defense Research Committee of the Office of Scientific Research & Development, Technical Aids, Div. 14, NTRC (predecessor agency to the CIA's Office of Scientific Intelligence). Trump was also a professor at M.I.T., and had his feelings hurt by Tesla's 1938 review and critique of M.I.T.'s huge Van de Graaff generator with its two thirty-foot towers and two 15-foot-diameter (4.6 m) balls, mounted on railroad tracks—which Tesla showed could be out-performed in both voltage and current by one of his tiny coils about two feet tall.^{[124][dubious – discuss]} Trump was asked to participate in the examination of Tesla's papers at the Manhattan Warehouse & Storage Co. Trump reported afterwards that no examination had been made of the vast amount of Tesla's property that had been in the basement of the New Yorker Hotel ten years prior to Tesla's death, or of any of his papers, except those in his immediate possession at the time of his death. Trump concluded in his report that there was nothing that would constitute a hazard in unfriendly hands.

After the FBI was contacted by the War Department, his papers were declared to be top secret. The personal effects were sequestered on the advice of presidential advisers; J. Edgar Hoover declared the case most secret, because of the nature of Tesla's inventions and patents.^[125] One document stated that "[he] is reported to have some 80 trunks in different places containing transcripts and plans having to do with his experiments [...]". Altogether, in Tesla's effects, there were the contents of his safe, two truckloads of papers and apparatuses from his hotel, another 75 packing crates and trunks in a storage facility, and another 80 large storage trunks in another storage facility. The Navy and several "federal officials" spent two days microfilming some of the material at the Office of Alien Properties storage facility in 1943, and that was it, until Oct., 1945.^[126]

Tesla's family and the Yugoslav embassy struggled with the American authorities to gain these items after his death because of the potential significance of some of his research. Eventually Mr. Kosanović won possession of the materials, which are now housed in the Nikola Tesla Museum.^[127]

Literary works[link]

Apart from doing pure work on inventing things, Tesla also wrote a number of books and articles for magazines and journals.^[128] Among his books are My Inventions: The Autobiography of Nikola Tesla, The Fantastic Inventions of Nikola Tesla and The Tesla Papers.

A number of Tesla's writings are freely available on the web,^{[129][130][131]} including the article The Problem of Increasing Human Energy which he wrote for The Century Magazine,^[132][133] and the article Experiments With Alternate Currents Of High Potential And High Frequency published in his book Inventions, Researches and Writings of Nikola Tesla.^[134][135]

Legacy and honors[link]

Nikola Tesla on contemporary 100 Serbian dinar banknote.

Nikola Tesla Corner in New York

• The tesla (symbol T) – compound derived SI unit of magnetic flux density.^[136]
• Tesla – a crater on the far side of the moon of 26 kilometers in diameter at −2,0° width, −132.0° height.^[137]
• 2244 Tesla – a minor planet.^[137]
• TPP Nikola Tesla – the largest power plant in Serbia.
• The rock band Tesla takes its name from Nikola Tesla.^[138]
• An electric car company, Tesla Motors, named their company in tribute to Tesla.^[139]
• The Belgrade Nikola Tesla Airport is named in his honor.^[140]
• Google honoured Tesla on his birthday on 10 July 2009 by displaying a doodle in the Google search home page, that showed the G as a tesla coil.^[141][142]
• The Czechoslovakian electro-technical company Tesla
• Tesla Motors, a manufacturer of electric cars based in Palo Alto, California, is named for him.
• The street sign “Nikola Tesla Corner” at the corner of the 40th Street and 6th Avenue in Manhattan
• The United States Postal Service honored Tesla with a commemorative stamp in 1983.
• Tesla was inducted into the Inventor’s Hall of Fame in 1975.
• The Nikola Tesla Award^[143]

Monuments[link]

Nikola Tesla monument by Les Drysdale in Niagara Falls, Ontario.

The Nikola Tesla Memorial Centre located in his birthplace of Smiljan near the town of Gospić in Croatia opened in 2006 features a statue of Tesla designed by sculptor Mile Blažević.^[144][145] On 7 July 2006 on the corner of Masarykova and Preradovićeva streets in the Lower Town area in Zagreb the monument to Tesla was unveiled. This monument was designed by Ivan Meštrović in 1952 and was transferred from the Zagreb-based Ruđer Bošković Institute where it had spent previous decades.

A monument to Tesla was established at Niagara Falls, New York. This monument, sculpted by Frano Kršinić and portraying Tesla reading a set of notes, was presented to the United States by Yugoslavia in 1976 and is an identical copy of the monument standing in front of the University of Belgrade Faculty of Electrical Engineering. Another monument to Tesla, featuring him standing on a portion of an alternator, was established at Queen Victoria Park in Niagara Falls, Ontario, Canada. The monument was officially unveiled on 9 July 2006 on the 150th anniversary of Tesla's birth. The monument was sponsored by St. George Serbian Church, Niagara Falls, and designed by Les Drysdale of Hamilton, Ontario. Drysdale's design was the winning design from an international competition.

In 1994, acting on the advice of the President's Advisory Council on Historic Preservation, a formal nomination process was initiated by the Tesla Wardenclyffe Project seeking placement of the Wardenclyffe laboratory-office building and the Tesla tower foundation on both the New York State and National Registers of Historic Places. This would result in the creation of a monument to Tesla out of the Wardenclyffe site itself.^[146]

Portrayals in popular culture[link]

Nikola Tesla has appeared in popular culture as a character in books, films, radio, TV, music, live theatre, comics and video games. The lack of recognition received by Tesla during his own lifetime has made him a tragic and inspirational character well suited to dramatic fiction. The impact of the technologies invented by Tesla is a recurring theme in several types of science fiction.

See also[link]

Electronics portal

• Electrical Experimenter
• List of Tesla patents
• Timeline of low-temperature technology

References[link]

Notes[link]

Sources[link]

Further reading[link]

Publications[link]

Journals[link]

Filmography[link]

External links[link]

This article's use of external links may not follow Wikipedia's policies or guidelines. Please improve this article by removing excessive or inappropriate external links, and converting useful links where appropriate into footnote references. (October 2011)

Find more about Nikola Tesla on Wikipedia's sister projects:
	Images and media from Commons
	Quotations from Wikiquote
	Textbooks from Wikibooks

• The Nikola Tesla Museum
• Original Tesla's patents presented in documentary movie by Museum Nikola Tesla.
• Nikola Tesla Niagara Falls Power
• Tesla Resource Surrounding the PBS "Master of Lightning" documentary
• World of Scientific Biography: Nikola Tesla, by Wolfram Research
• Nikola Tesla Page
• Tesla's grand-nephew William H. Terbo's site
• Nikola Tesla, Forgotten American Scientist
• Tesla Wardenclyffe Project, Long Island New York. Mission is the adaptive reuse of the Wardenclyffe laboratory building.
• Nikola Tesla's Father: Milutin Tesla
• Tesla: The European Years
• Jim Bieberich's The Complete Nikola Tesla U.S. Patent Collection
• Online archive of many of Tesla's writings, articles and published papers
• Seifer, Marc J., and Michael Behar, Electric Mind, Wired Magazine, October 1998.
• Works by Nikola Tesla at Project Gutenberg
• Nikola Tesla's FBI file in pdf
• Nikola Tesla Complete Patents in pdf
• Kenneth M. Swezey Papers, 1891–1982, Archives Center, National Museum of American History, archival resources.
• The Case Files of Nikola Tesla, Franklin Institute
• Booknotes interview with Jill Jonnes on Empires of Light: Edison, Tesla, Westinghouse and the Race to Electrify the World, October 26, 2003.

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