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N kola Tesla,the father of today's AC electrical system

and other key inventions,

often failed to bring his visionary ideas

to real-world fruition

hen members of the Chicago Com-mercial Club arrived to hear a lec-ture by the famed electrical inven-

Nikola Tesla on May 13, 1899, they weretIed by the sight of an arti6ciallake sitting.1e middle of the auditorium. Everyone knew: Tesla-the man who had devised the alter-ing-current (AC) system that brought elec-ity into people's homes and businesses-wasaster showman. Six years earlier at Chicago'sumbian Exposition, for example, the dapperineer had dazzled spectators by sendingI,OOO-volt shocks coursing through his body.w the audience was abuzz, wondering whatla was going to do with his miniature lake

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and the six-foot boat that floated on its surface.Abruptly, the craft began to motor around

the pool on its own, with lights blinking. Fromthe side, Tesla operated a remote-control unitthat conveyed commands to the boat via invis-ible radio waves. The crowd was astonished.He then invited individuals to shout out com-mands: "Turn left! Flash the lights!" Using hiswireless transmitter, Tesla signaled the boat,and it executed the requested maneuvers [seeillustration on page 83]. With the Spanish-American War having Just come to an end, theaudience was impressed by Tesla's proposal toarm a larger vessel with dynamite and thensteer it by remote control toward an enemy na-

SCIENTIFIC AMERICAN 79

As he admired the Budapest sunset, TESLA ENVISIONEDthe solution to his motor problem.

TWO-PHASE alternatina-current (AC) induction motor was built byTesla in 1887. By energizing pairs of Induction coils on either sideof the stator with two separate out-or-phase alternating currents,he created a rotatlna magnetic field that induced an opposlnaelectric field In the rotor, causina It to turn.

val ship. Here, more than a century ago, was a proto-type for the guided missile.

Despite this spectacular demonstration, Tesla neverconverted his remote-control boat into a full-fledgedweapon. His failure to do so is emblematic of a largertheme that permeated his life-a profound idealism thatonly occasionally reached practical reality. Throughout

80 SCIENTIFIC AMERICAN

his career, Tesla strove to find the perfect principle onwhich to base a revolutionary invention. Having identi-fied a grand concept, he was willing to patent and dem-onstrate it, but he often left it to others to carry out thedown-and-dirty work of engineering a moneymakingproduct. Sadly, as his career progressed, the famous in-ventor found it increasingly difficult to convince prospec-tive backers to help with the messy process of commer-cialization. As a result, he grew ever more disappointedwith and disconnected from the world.

Motor VisionaryTESLA WAS BORN on July 10, 1856, to a Serbianiam-ily living on the frontier of the Austro-Hungarian Em-pire, in what is today Croatia. As a teenager, Tesla choseto study engineering at the Joanneum Polytechnic Schoolin Graz, Austria. There the youthful scholar eagerly at-tended the physics lectures presented by Jacob Poeschl in1876 and 1877.

During Poeschl's lectures, Tesla first started thinkingabout what would become his most important invention,an improved AC motor. One day he watched his profes-sor attempt to control the troublesome sparking of a di-rect-current (DC) motor's brush commutator-copper-wire electrical contacts that reverse the current twiceduring each rotation so that the resulting opposing mag-netic fields keep the rotor turning. Tesla suggested that itmight be possible to design a motor without a commuta-tor. Annoyed by the student's impudence, Poeschllec-tured on the impossibility of creating such a motor, con-cluding: "Mr. Tesla may accomplish great things, but hecertainly never will do this." The rebuke, however, mere-ly stoked the fires of the youth's ambition. Tesla puzzledincessantly about how to make a spark-free motor as hepursued his studies in Graz and thin in Prague.

In 1881 Tesla traveled to Budapest, hoping to work forfamily mends, Tivadar and Ferenc Puskas. An ambitiouspromoter, Tivadar had previously convinced Thomas A.Edison to give him the commercial rights to introduce in-ventions developed by the Wizard of Menlo Park in conti-nental Europe. The Puskas brothers were planning to con-struct a telephone exchange in Budapest using Edison'simproved telephone design. Unfortunately, they were un-able to hire anyone immediately. While waiting, Tesla fellseriously ill. He only recovered with the help of a collegefriend, Anthony Szigeti, who encouraged the sick man towalk each evening to help regain his strength.

It was during one of these strolls with Szigeti thatTesla had an epiphany about motors. As they admiredthe sunset, Tesla suddenly envisioned using a rotating

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"CITY OF LIGHT" at tha Columbian Expo'ition It thl 1893 ChicaloWorld', Fair wa, powlrld by 12 1,OOO-hor'epowlr AC leneratorsofTe,II" deslln. The 27 million visitor, came awlY from the fairknow!nl thlt AC power wa, the future of electricity.

magnetic field in his motor-a major break with conven-tion. The young Serb's insight was to invert the standardpractice: rather than changing the magnetic poles in therotor, he would alter the magnetic field in the stator. Thisconfiguration would eliminate the need for the sparkingcommutator. Tesla saw that if the magnetic field in thestator rotated, it would induce an opposing electric fieldin the rotor, thus causing the rotor to turn. He surmisedthat the rotating magnetic field could be created using ACinstead of DC, but at the time he did not know how to

achieve this feat.

RII' to Riche,T E S LAS T RUG G LED for the next five years to acquire the

practical knowledge he needed to realize his motor. After

he had helped the Puskas brothers build their telephone

exchange in Budapest, Tesla moved with Tivadar to Paris,

where they both went to work for the Societe ElectriqueEdison instal1ing incandescent lighting systems. In 1884

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HYDROELECTRIC GENERATORS produclna three-phlae AC powerwere inataliid by Weatinahouee enaineereln Nilalrl Falla. N.Y., In1996.lnitlllly, they trlnemltted electricity only the 2S mll,a to9uffefo, N.Y., but within I fewyeara. power lints to New York Cityaet Broldway Iblln with lIaht.

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Tesla transferred to the Edison Machine Works in NewYork City. Unfortunately, he had almost no personal con-tact with the renowned inventor. While there, the Serbianinventor nearly told Edison about his motor idea. "It wason Coney Island," he recalled, "and just as I was going toexplain it to him, someone came and shook hands withEdison. That evening, when I came home, I had a fever andmy resolve rose up again not to speak freely about [mymotor] to other people." A few months later, after Teslahad completed the design of an improved arc lighting sys-tem (illumination based on electric sparks leaping the gap

SCIENTifiC AMERICAN 81

runnlnllround the lib, to achieve the.e spectacular effects. Inthe Image at bottom (taken at his New York City lab in 1898), Tesllwatches as powerful electromaanetlc fields Induce electricalstreamers packina nearly half I million volts In the front coli.

82 SCIENTIFIC AMERICAN

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between two electrodes), his managers reneged on a prom-ised bonus, so the ambitious engineer quit in disgust.

Tesla was quickly hired by two business promotersfrom Rahway, N.J., Benjamin A. Vail and Robert Lane,who encouraged him to patent his arc lighting system sothey could commercialize it. Tesla unwisely assigned thepatents to the shifty pair, trusting that they intended tomanufacture equipment and compete with Edison. Vailand Lane, however, decided that the real financial op-portunity lay in operating an electric lighting utility. Soonce Tesla had his arc lighting system running in Rah-way, his backers fired him and reorganized the firm. Ut-terly destitute after being abandoned, Tesla was forced

to dig ditches.Despite enduring a year of backbreaking hardship,

Tesla mustered the energy in March 1886 to file a patentapplication for a thermomagnetic motor-a novel devicepowered by heating and cooling magnets. Discussionsabout his invention with the foreman at his ditchdiggingjob led to an introduction to Charles Peck, a clever at-torney. Intrigued by the thermomagnetic motor concept,Peck offered to underwrite Tesla's research. Because Peckwas not a technical expert, he invited Alfred S. Brown, asuperintendent at Western Union, to join him in support-

ing Tesla.Peck and Brown rented a laboratory for T esla in low-

er Manhattan, where the immigrant inventor devotedhimself initially to developing the thermomagnetic mo-tor. When that concept proved unworkable, Peck pushedTesla to work on perfecting AC motors. Building on hisBudapest vision, Tesla began experimenting with mul-tiple alternating currents in a motor. This approach wasunconventional because most contemporary experiment-ers employed a single alternating current in their systems.By September 1887 Tesla discovered that he could pro-duce a rotating magnetic field by feeding two separatealternating currents into pairs of coils set on oppositesides of the stator [see illustration on page 80]. In modernparlance, the two currents are 90 degrees out of phase,and the motor runs on two-phase current. Elated, Teslasubmitted several patent applications that broadly cov-ered the principle of a rotating magnetic field. In thesefilings, he introduced the idea that multiphase AC couldtransmit power over substantial distances, a notion thatwas to become important later.

When it became clear that Tesla's AC motor had realpromise, his backers began pondering how to promote it.Peck and Brown planned to sell Tesla's patents to the high-est bidder, rather than to manufacture motors. Towardthat end, they arranged for Tesla to lecture before theAmerican Institute of Electrical Engineers in May 1888.The talk received extenSive coverage in electrical journalsand soon attracted the interest of George Westinghouse,who had made a fortune manufacturing air brakes andsignal systems for railroads. At this time, electric lighting

MARCH 2005

Tesla believed that his SIGNALS REACHED MARS and thathe had received a return message from Martians.

companies were considering shifting from DC to AC, be-cause AC could be transmitted over longer distaO(es andthus reach more customers. Whereas Edison focused onDC technology, Westinghouse had bet on AC, and so Peckand Brown were able to convince him to pay handsomelyfocTesla's patents. In July 1888 Westinghouse offered thegroup $25,000 in cash, plus 550,000 in notes and a roy-alty of $2.50 per horsepower for each motor manufac-tUred. Tesla generously gave five ninths of the proceeds tohis two supporters while retaining the rest for himself.

Westinghouse hoped Tesla's motor could be used todrive streetcars, so Tesla went to Pittsburgh to adapt hisdesign to this application. The inventor and the Westing-house engineers were, however, Stymied by technical dif-ficulties. Because his motor required two alternating cur-rents and four wires, it could not be merely dropped intoexisting single-phase AC systems; one would need to in-stall additional wires to the network. Although Tesla de-veloped several two-wire motors, these so-called split-phase designs ran best on currents of 50 cycles per secondor less. At that time, Westinghouse single-phase systemsemployed 133-cycie current so customers would not seetheir incandescent lamps flickering.

Westinghouse engineers eventually solved these prob-lems by modifying Tesla's motor and developing a newAC system using three-phase, 60-cycle current. Westing-house demonstrated this new technology in dramaticfashion in 1895 by building a hydroelectric station atNiagara Falls, a plant that subsequently transmittedpower across the 25 miles to factories in Buffalo, N.Y.Thus, Tesla's AC motor and multi phase AC systemformed the basis for today's North American power-dis-tribution system [see bottom illustration on page 81].

Resonating with EnergyLONG BEFORE the Niagara station came on line, how-ever, Tesla grew restless and left Westinghouse. He hadcome up with the ideal AC motor but wasn't interested inworking out the details.

Drawing on his royalties, in 1889 Tesla established anew laboratory in New York City. To attract public at-tention and new investors, he now cultivated the imageof an eccentric genius. Just as reporters had publicizedEdison's exploits at Menlo Park in the 1870s, so theyflocked to Tesla's laboratory in the 1890s to cover hissensational discoveries and dramatic pronouncements[see bottom illustration on opposite page].

Searching for a way to create an arc light for use onAC networks, Tesla now found a new fundamental idealon which to focus: high-frequency electrical phenomena.

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RADIO. CONTROLLED BOAT was unveiled by Teslaln 1898. The nextyear he demonstrated to the Chicago Commercial Club that he could

run a boat (view from above) without touching it, making it turn,accelerate and fluh its lights whenever he sent slanals to it. Someexperts relard the boat's circuitry as a progenitor of the basic AND

lollc used in modern computers.

If one could build a practical motor using 60-cycle AC,he wondered, what could be made of current with a fre-quency of 10,000 cycles per second? Whereas Tesla hadcombined magnetic induction coils, resistors and capac-itors to fashion his split-phase motors, he now connectedinduction coils and capacitors in new configurations toproduce high-frequency currents.

The inventor investigated this grand concept for thenext 15 years. By likening a capacitor to a storage tankand an induction coil to a coil spring, Tesla realiud thata properly configured circuit could amplify electrical sig-nals and raise them to ever higher frequencies and volt-ages. Exploiting this insight, he constructed huge "mag-nifying transmitters"-today called Tesla coils-thatgenerated sparks more than 135 feet long [see top illus-tration 01J opposite page). Tesla funher appreciated thatresonance opened the way to tuning radio signals. Givinga transmitter a particular capacitance and inductancewould generate signals at a desired frequency; likewise,endowing a receiving circuit with the same capacitanceand inductance would allow it to respond to signalstransmitted at that original frequency.

Drawing on the fundamental idea of electrical reso-nance, Testa simultaneously pursued inventions in light-

W. BERNARD CARLSON is associate professor of science, technoloayand society in the School of Enaineerina and Applied Science at the

University of Virginia. He received his doctorate in the history of sci-

ence and sociology from the University of Pennsylvania in 1984. and

he studied business history as a postdoctoral fellow at the Harvard

8usiness School from 1988 to 1989. He recently finished the seven.

volume Technology In World History, which will be published in 2005 by

Oxford University Presl. With support from the Alfred P. Sloan Founda.

tion, Carlson is currently completing a bioaraphy of Tesla to be pub-

lished by Princeton University Press.

SCIENTIFIC AMERICAN 83

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MARK TWAIN (Samuel Clemens) demonstrates the wirelesstransmission of power. A large resonating coil (nor visible) hasinduced a high-voltage current in the wire loop he holds. Thecurrent passed harmlessly through Twain's body yet caused theincandescent bulbs to glow. Tesla is seen (obscuredarfar/eft)operating the apparatus's controls.

ing, wireless communications and the wireless distribu-tion of power. Hoping to develop a high-efficiency lampto replace Edison's incandescent bulb, the brilliant inven-tor not only created early fluorescent lamps but also ob-served that a vacuum tube could detect radio waves.T esla did not follow up on this observation, however, andJ. A. Fleming and Lee De Forest subsequently developedtheir own radio tubes.

TESlA IS SEEN IN HIS NEW YORK City office in 1916. The Inventoroften crossed the street to Bryant Park to feed the piaeons there.The drawinas behInd Tesla depict his steam engine desian.

84 SCIENTIFIC AMERICAN

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Having perfected the circuits needed to transmit andreceive radio waves, Tesla tested them using antennassuspended from balloons floating over his downtownlaboratory and his uptown Manhattan hotel. But just ashe began to get promising results, his lab was destroyedby fire in March 1895, and all his research apparatus andnotes were lost.

Broadcasting Power GloballyIN THE SPRING OF 1899 Tesla closed his rebuilt NewYork laboratory and constructed a facility at the foot ofPikes Peak in Colorado Springs, Colo. There the inventortackled what he believed would be the most importantapplication for electromagnetic waves: the wireless trans-mission of power around the world. During that period,it seemed as if all of America was being wired. The de-mand for electricity appeared to be insatiable, so hedreamed of trumping the burgeoning landline networksby distributing both power and messages without wires.

Tesla's newest dream was based on electrical reso-nance. Like other early wireless researchers, he viewedthe relation between transmitter and receiver as twofold.First, the transmitter sent radio waves through the air tothe receiver. Then, because both devices were groundedto the earth, a return current passed through the groundfrom the receiver to the transmitter. Unlike everyone else,who focused on transmitting radio waves through theatmosphere, however, Tesla decided to concentrate onthe earth-borne current. Why not, he thought, have thetransmitter send waves through the earth to the receiverand then use the atmosphere for the return circuit? Teslaimagined that it should be possible for a transmittingstation to pump electromagnetic energy into the earth'scrust until the planet's electrical resonant frequency wasreached; then, with the whole globe pulsing with energy,it could be tapped by receiving stations allover the world.Tesla assembled several large magnifying transmitters atColorado Springs to test this theory and convinced him-self that they had successfully broadcast power aroundthe world. (Tesla also believed that his signals had reachedMars and that he had received a return message from

Martians!)Satisfied that power could be transmitted around the

globe underground, he returned to New York City in1900. So certain of success was he that he took rooms inthe luxurious Waldorf-Astoria Hotel. Tesla then wrote a60-page treatise for Century magazine entitled "TheProblem of Increasing Human Energy." His promotion-al efforts paid off, and in 1901 tycoon J. Pierpont Mor-gan invested $150,000 in Tesla's wireless-power scheme.Tesla rapidly spent this advance, sparing no expense inoutfitting a new laboratory in Wardenclyffe, on the northshore of Long Island, N.Y. Despite Morgan's refusal toprovide more cash and Tesla's failure to produce positivetechnical results, the inventor nonetheless built a 187-

MARCH 2005

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foot antenna tower in Wardenclyffe [see illustration atright]. Even with his connections to New York's moneyedelite, however, Tesla could not-secure the funds he need-ed to complete his project and thereupon suffered a ner-

vous breakdown.

Late, LIft and Lt.acyFOLLOWING HIS PARTIAL RECOVERY, Teslahopedto raise money to resume work at Wardenclyffe by shift-ing his creative effons from electrical to mechanical en-gineering. Aware that power plants were replacing pis-ton-based reciprocating steam engines with more effi-cient rotary steam turbines, he began investigating aradical bladeless turbine design. Like his other inven-tions, the bladeless turbine was based on a grand idea.Just as a rotating magnetic field "dragged" the rotoralong in his AC motor, so Tesla thought it possible tohave steam drag around a series of thin, closely spaceddisks fastened to a turbine's shaft via viscous forces-shearing stresses that depend on a fluid's flow velocity.Testa's turbine had to operate at speeds exceeding 10,000revolutions per minute-unfortunately, much too fastfor any thin steel disks to withstand.

Although Tesla was unable to convince anyone tomanufacture his bladeless turbine, he was able to patentan automotive speedometer based 00 the same principle:the use of viscous forces that cause closely placed disks tospin. During the next two decadest he lived off the royal-ties from his speedometer. T esla meanwhile wrote articlesfor popular magazines in which he speculated on the fu-ture of electricity and radio. Gradually, however t he grewdepressed and finally became an itinerant recluset movingfrom hotel to hotel as the bills came due.

To mark Tesla's 75th birthday, in 1931, Time maga-zine ran a cover story in which the inventor held forth onsignaling the stars with his "Teslascope"-a giant radiotransmitter. Enjoying his regained celebrity, he held an-nual press conferences on his birthday. During theseevents, Tesla warned about the dangers of global war andargued that disaster could be avoided only by developinga super weapon that could maintain a balance of terror.The ultimate deterrent, he claimedt was a ray gun or par-ticle-beam device that could direct immense amounts ofenergy at enemy airplanes, ships and armies. In 1937,while Tesla was taking his daily stroll around the city, hewas struck by a taxi. The eminent inventor never fullyrecoveredt and he died on January 8, 1943.

Tesla left a mixed legacy. On the one hand, he is ac-knowledged as the father of the AC motor, and in 1956the "tesla W was adopted as the international unit of mea-

sure for the flux density of magnetic fields. On the otherhand, his many colorful predictions led him to become apatron saint for groups who hold nonmainstream spiri-tual beliefs. Fascinated by Tesla's claims of uncoveringthe mystical secrets of the universe, these fans contend

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WARDENCl YFFE TOWER, It 18? feet till. .tood nllrthellb Te.11constructed In 1901 In whit I. nowShorehlm,lona 1.llnd. Theflcllltlj wI,lntended both fortrln.ltllntlcwlrlle..communlc'tlon. and radio broldCI'tlna. I' weill' for aloblltrln,mll,lon of electric power.

that powerful individuals such as Edison and Morganhad conspired to keep Tesla from perfecting his inven-tions and revolutionizing the world.

Exaggerated claims and conspiracy theories notwith-standingt Tesla made enormous contributions to engi-neering. His ability to focus on fundamental principleswas his greatest strengtht but it was also his biggest weak-ness. AU too oftent Tesla became intoxicated by the beau-ty of his basic conceptst so much so that he was unwillingto work out the practical details of his inventions. .

My Invention,: The Autobloaraphy of Mlkola Te,la. Edited by Ben Johnston.(Originally published in Electrical Experimenter in 1919.) Reprinted byHart Brothers, Williston, Vt., 1982.

The Invention" Re,earche" and Wrltlna' of Mlkola Te,la. ThomasCommerford Martin. (Originally published in 1893.) Reprinted by8arnes a. Noble, 1995.

Prodlae' Genius: The Life of Mlkole T..la. John J. O'Neill. (Orlainallypublished by Ives Washburn, New York, 1944.) Reprinted by KessingerPublishing Company, 1996.

Wizard: The Life and Time, of Mlkola Te,la. Marc J. Seifer.81rch Lane Press,1996.

Tha T.,I. Collection, Vols. 1-23. Full-text periodical/newspaper bibliography.Edited by Iwona Vujovic. The Tesla Project, 1998.

Te,'a: MI'ter of Llahtnlna. Margaret Cheney and Robert Uth.Barnes a. Noble, 1999.

Empire. of Llaht: Edl.on, Te,ll, We'tlnahou.., Ind the RlC' to Electrifythe World. Jill Jonnes. Random House, 2003.

Nikola Tesla Museum, Belgrade, Serbia: w_.te"I-mu,eum.ora

Tesla Wardenclyffe Project: www.te"I,clence.ora/

SCIENTIFIC AMERICAN 85