Nikola Tesla (1856–1943) was born to Serbian parents in Smiljan, a village in today's Croatia, then part of the Austrian Empire. His father was a priest; his mother, he said, was an inventor of household tools. He studied engineering at the polytechnic in Graz, worked for telephone and electric companies in Budapest and Paris, and moved to New York in 1884. In 1919 he told his story in a magazine series, My Inventions.
Key idea
The problem
Motors of the time ran on direct current and needed a commutator with brushes, sliding contacts that sparked and wore out. As a student in Graz, Tesla watched one.
While Prof. Poeschl was making demonstrations, running the machine as a motor, the brushes gave trouble, sparking badly, and I observed that it might be possible to operate a motor without these appliances. But he declared that it could not be done.
How the idea came
Tesla says he tried for years, picturing machines in his mind. In February 1882, walking in a Budapest park with a friend at sunset and reciting lines from Goethe's Faust, the answer came.
As I uttered these inspiring words the idea came like a flash of lightning and in an instant the truth was revealed. I drew with a stick on the sand the diagrams shown six years later in my address before the American Institute of Electrical Engineers, and my companion understood them perfectly.
Why it works
Worked example: How fast does the field turn?
- 60 turns each second.
- $60 \times 60 = 3600$ turns per minute.
Answer: 3,600 turns per minute.
Working for Edison, and on his own
In New York Tesla worked for about six months in 1884 for an Edison company, improving direct current dynamos. He left after a dispute about pay; in his telling, he had been promised a large bonus that was never paid, and the story is told differently by others. In 1887 he set up his own laboratory, and in May 1888 described his AC motors in a lecture to the American Institute of Electrical Engineers. George Westinghouse bought the patents.
The war of the currents
In the late 1880s, Edison's companies sold direct current (DC) and Westinghouse sold alternating current (AC). Both sides had good arguments at the time:
| Direct current (Edison) | Alternating current (Westinghouse, Tesla) | |
|---|---|---|
| Strengths in the 1880s | Already working in cities; good motors and meters; could charge batteries | A transformer can step it up to high voltage for long wires and down again for homes, wasting less power on the way |
| Weaknesses in the 1880s | Power stations had to be within a mile or two of customers | No practical motor until Tesla's; high voltages raised safety worries |
Edison's side ran a public campaign about the dangers of AC's high voltages; the Westinghouse side answered that well-built AC was safe. AC won for power grids, mainly because transformers made long-distance power cheap. Westinghouse lit the 1893 World's Fair in Chicago with AC, and in 1896 AC power from Niagara Falls reached Buffalo, over 20 miles away. DC never disappeared: batteries, phones and computers run on it, and some very long modern power lines use high-voltage DC.
Story or history?
Tesla is often told as a lone genius robbed by Edison. The record is more mixed. Galileo Ferraris in Italy found the rotating magnetic field independently at about the same time. Tesla was paid well for his patents, though he later gave up royalties to help Westinghouse's company, and died with little money. And Edison, though wrong about AC, was a great inventor in his own right. Both men's own words should be read as their side of the story.
| When | What happened |
|---|---|
| 1856 | Born in Smiljan |
| 1875–1878 | Studies at the polytechnic in Graz; sees the sparking Gramme machine |
| 1882 | The rotating field idea in a Budapest park |
| 1884 | Arrives in New York; works for an Edison company |
| 1887 | Opens his own laboratory |
| 1888 | Lecture on AC motors; Westinghouse buys the patents |
| 1891 | Patents the Tesla coil |
| 1893 | AC lights the World's Fair in Chicago |
| 1896 | Power from Niagara Falls reaches Buffalo |
| 1919 | My Inventions published |
| 1943 | Dies in New York |
Worked example: From idea to lecture
- $1888 - 1882 = 6$.
Answer: 6 years, just as he says: "shown six years later."
What it led to
Induction motors run fans, pumps, factory machines and many electric trains. The power grid that reaches nearly every home is alternating current. The unit of magnetic field strength is named the tesla.
Common mistake
Read more: Nikola Tesla, Induction motor and War of the currents.