Nikola Tesla

I

INTRODUCTION

Nikola Tesla (1856–1943), Serbian American physicist, electrical engineer, and inventor. Tesla was one of the great pioneers of the use of alternating current electricity. Alternating current electricity changes in strength cyclically over time and is the type of electricity that power companies supply to homes today (see Electricity: Alternating Currents). Tesla invented the alternating current induction generator, a device that changes mechanical energy into alternating current electricity, and the Tesla coil, a transformer that changes the frequency of alternating current. See also Electric Motors and Generators; Transformer.

II

TESLA’S LIFE

Tesla was born to Serbian parents in Smiljan, Croatia (then part of Austria–Hungary). His father was a priest of the local Serbian Orthodox Church. Tesla was very clever as a child and liked to write poetry and experiment. His parents wanted him to follow his father and become a priest, but Tesla developed an interest in scientific pursuits while he was at the Real Gymnasium in Karlovac from 1871 to 1877. He studied engineering at the Technical University in Graz, Austria, from 1877 to 1880. In 1880 he went to the University of Prague to continue his studies, but the death of his father caused him to leave without graduating.

In 1881 Tesla went to Budapest as an engineer for a telephone company and a year later took up a similar position in Paris. He went to the United States in 1884 and worked for American inventor Thomas Edison for a year before setting up his own workshop. For much of his time in the United States, Tesla worked with American industrialist George Westinghouse, who bought and successfully developed Tesla's patents, leading to the introduction of alternating current for power transmission. Tesla became a United States citizen in 1889. After his mother’s death in 1892, he became increasingly withdrawn and eccentric. In 1912 both he and Edison were proposed for the Nobel Prize in physics, but Tesla refused to be associated with Edison, who he believed had conducted an unscrupulous campaign for the adoption of direct current. Neither inventor received the prize. Tesla neglected to patent many of his discoveries and made little profit from them. He lived his last years as a recluse and died in New York.

III

TESLA’S WORK

Tesla saw a demonstration of a direct current electric motor and generator in 1878 while he was a student at Graz. The generator that Tesla saw had brushes that came into contact with a piece of metal called a commutator. He thought that the machine could be improved by eliminating the brushes and commutator, which were sources of wear. His idea for the induction generator came to him four years later. An induction generator uses mechanical energy from a spinning piece of iron to produce electrical energy. He developed the idea of spinning a piece of iron between stationary coils of wire electrified by two alternating currents not quite in step with each other. The current through the coil produced a rotating magnetic field, which induced a current in the piece of iron, called a rotor. The induced current would alternate directions as the rotor spun. The current induced in the rotor could then be used to power electrical appliances. The machine could also be run backwards to change electrical energy into mechanical energy—if an electric current was applied to the rotor, the rotor would begin spinning. This device was called an induction motor when it changed electrical energy into mechanical energy. Like many of his other ideas, Tesla mentally applied his motor to all kinds of practical uses before he actually built a model.

Tesla built his first working induction motor in 1883. He found that he could raise little interest in his inventions in Europe. He set off for New York City, where he set up his own laboratory and workshop in 1887 to develop his motor in a practical way. Only months later he applied for and was granted a complicated set of patents covering the generation, transmission, and use of alternating current electricity. Because alternating current can be transmitted over much greater distances than direct current, it provides the power for most of our present-day machines. At about the same time he lectured to the American Institute of Electrical Engineers on his alternating current system. After learning about the talk, George Westinghouse quickly bought Tesla's patents.

Westinghouse backed Tesla's ideas and, as a demonstration, employed his system for lighting at the 1893 World Columbian Exposition in Chicago. Months later Westinghouse won the contract to generate electricity at Niagara Falls, New York. He used Tesla's system to supply electricity to local industries and deliver alternating current to the town of Buffalo, New York, 35 km (22 mi) distant.

After 1888 Tesla's interests turned to alternating currents at very high frequencies, or alternating currents that vary very rapidly over time. He felt these currents might be useful for lighting and for communication. First, he modified generators so that they produced high frequency current. He then decided that generating current at a lower frequency, then boosting it to a higher frequency would be more efficient. With that in mind, he designed the Tesla coil, a transformer that could change both the frequency and magnitude of an alternating current.

The Tesla coil is a combination of two circuits. Each circuit has a coil of wire, both wound together around a hollow tube. One of the coils is made of heavy wire and has just a few turns around the tube. The other circuit’s coil is made of finer wire wound many times around the tube. When an alternating current passes through the coil of heavy wire, it produces a magnetic field. The magnetic field induces current in the fine wire. Because of the differences in the wire and number of turns, the frequency of the current in the finer coil is much higher, and the voltage is also higher in the finer coil. Using this device, Tesla produced an electric spark 41 m (135 ft) long in 1899. He also lit more than 200 lamps over a distance of 40 km (25 mi) without the use of intervening wires. The high-frequency current of a large Tesla coil can energize the gas in lamps made of gas-filled tubes (such as neon lamps) from a long distance.

Tesla was also very interested in the possibility of radio communication. As early as 1897, he demonstrated remote control of two model boats on the lake in Madison Square Garden in New York City. In 1900 he began to construct a broadcasting station on Long Island in the hope of developing a project called “World Wireless.” By the early part of the next decade this project had proved too expensive for his backers and was abandoned. By the beginning of World War I (1914-1918) Tesla faced financial ruin. Westinghouse refused to provide Tesla with financial support after several significant failures, including the broadcasting station. Another major benefactor, American financier John Pierpont Morgan, died in 1913. Tesla spent the remainder of his life in seclusion. Many of his ideas have come to fruition at the hands of others. Tesla outlined a scheme for detecting ships at sea that was later developed as radar. Many of his inventions, including electrical clocks and turbines, remained in his head because he had no money to put them into practice.