Writer 1879: Solitary Journey in France

Chapter 653 Nonsense! Driven by electric current? Rotating magnetic field!

The reason why the other engineers present, including Edison, were shocked was simple—to this day, no engineer or scientist had "reverse engineered" the principle of an alternating current generator.

Currently, the motors manufactured by "Sorel-Tesla Electric" have sold quite a few on the market, and many engineers have bought them and disassembled them countless times.

Edison did just that—but even if they could replicate a similar device, no one could discover the principle of "rotating magnetic field" from a physical perspective.

Someone immediately shouted, "A rotating magnetic field? Isn't the direction of the magnetic field determined by the electric current?"

Nikola Tesla smiled slightly: "Gentlemen, I know what you're thinking. You're thinking, rotating magnetic fields? What kind of new trick is this?"

His gaze swept across the audience: "The reason why everyone is confused is that every electrical engineer in this era—including myself—is a 'native' of direct current."

This word elicited a murmur of laughter from the audience, but Tesla didn't laugh; his expression remained serious.

“In the past, all the motors we were familiar with relied on mechanical commutators and brushes to switch the direction of current, so we believed that ‘the direction of current determines the direction of the magnetic field.’”

"In this view, the magnetic field should be static, or at most pulsating. But in my opinion, the magnetic field is neither static nor pulsating; it can also rotate."

It can not only rotate, but also drive other objects to rotate, without requiring any mechanical connection. Of course, this sounds abstract because it cannot be directly observed.

Someone couldn't help but exclaim, "If you can't observe it directly, how do you know the magnetic field can rotate?"

When Nikola Tesla heard this question, he opened his arms as if to embrace the entire room: "Let me tell you how I discovered it."

The meeting room fell completely silent. Everyone's attention was focused on Tesla; even Thomas Edison leaned forward, trying to hear more clearly.

"At that time, I was the chief engineer at the Budapest Telephone Bureau. One evening in February, I was walking along the park's walking path with my friend Anthony Sighetti."

We discussed poetry as usual—that day it was Goethe's turn. I recited the description of the setting sun in *Faust*, my gaze following the sunset—

'The sun sets and disappears, a new day begins / Ah, alas, I have no wings to soar into the sky / To forever chase after it!'

Suddenly I realized something. I saw—I really saw—the sun wasn't setting, it was spinning! Spinning eternally on the stage of the universe.

And at that very moment, I captured it with my mind—a rotating magnetic field!

If the person on stage hadn't already produced a physical motor that had taken over the American market, he would have been ousted from the stage based solely on his narration.

Frankly speaking, most of the people sitting here have been studying the electrical field for many years and will not tolerate a foreigner spouting nonsense on stage.

But now everyone listens intently, believing they are witnessing a moment in scientific history akin to "Sir Isaac Newton and the apple."

Nikola Tesla, on the other hand, was completely absorbed in his memories—

"The problem that had been troubling me for years—how to drive a motor with electric current without the need for commutators and brushes—suddenly became crystal clear."

I had Anthony find a twig, and we drew the first sketch on the sandy ground of the park path—”

As Nikola Tesla spoke, he walked to the blackboard, picked up a piece of chalk, and drew two perpendicular coils with a circle in the middle.

He then marked the direction of the current on the two coils and drew several curves in the middle circle: "Let me show you the principle."

He first pointed to the first coil: "When the current in the first coil reaches its peak, it generates a northward pull."

Then he pointed to the second coil: "At the same time, the current in the second coil is just starting to rise from zero. After a quarter cycle, the current in the first coil decays, the second coil reaches its peak, and the pull turns eastward."

His chalk moved across the blackboard, drawing the changes in the direction of the magnetic field.

"Gentlemen, magnetic field lines are not stationary ropes. They can move. If we precisely time the two currents—keeping them offset by a quarter-cycle—the resulting magnetic field will not fluctuate in strength, but will rotate continuously."

The audience was completely silent. These top American electrical engineers seemed like a group of elementary school students attending their first science lesson.

Thomas Edison's face was terribly gloomy, and his mood was very complicated—on the one hand, he regretted missing out on the genius Nikola Tesla.

He couldn't imagine how many patents and miracles this frail young man from Eastern Europe would create for him if he worked in his laboratory.

Today, Nikola Tesla has not only slipped away right under his nose, but has also become the biggest obstacle to his building of an "electric empire."

On the other hand, he also felt embarrassed because everyone else was listening with great interest, while he was the only one struggling.

Edison had a very weak foundation in the principles of physics and mathematics; he focused only on the parts of these disciplines that were most relevant to practical applications.

Tesla’s current pronouncements on stage are almost purely theoretical, and still purely theoretical in a way that cannot be directly observed, which makes him feel somewhat embarrassed.

On the platform, Nikola Tesla had already drawn a cylindrical cage on the blackboard, using several vertical lines to represent copper bars and two rings at the top and bottom.

Someone in the audience immediately exclaimed, "That's Mr. Faraday's cage!"

Tesla nodded: "Yes, this is Mr. Faraday's cage. Now, place the cage in the center of that rotating magnetic field. We don't need to connect any wires to this cage, nor do we need brushes or a commutator."

He drew arrows around the cage with his chalk to represent the rotating magnetic field.

"When the magnetic field rotates, it will 'cut' the copper strip, and at the same time, the induced current will flow in the copper strip, generating its own magnetic field, trying to resist the change of the magnetic field."

The result is that the 'copper cage' will begin to rotate following that unseen magnetic field; it is the 'rotor' inside the motor.

After saying that, he turned around and said, "When I first arrived in Paris, I tried to build the first motor like this. The rotor started to turn the moment I switched it on."

It is very smooth and quiet, without sparks or friction, and transmits only pure electromagnetic force—Mr. Edison, I actually demonstrated it to Mr. Ferguson.

But Mr. Ferguson told me to focus on improving DC motors and designing and installing household lighting circuits, so I stopped my research.

Thomas Edison certainly knew who he was talking about: Charles Ferguson, the general manager of the "Edison Electric Light Company in Paris".

Almost everyone looked at Edison with mocking eyes. Edison's face was as black as charcoal, but he couldn't just get up and leave.

Nikola Tesla did not press his advantage; he wasn't even mocking his former employer, but simply stating a fact with a hint of regret.

But this only made Edison more miserable. He knew Tesla, a pure technical genius, all too well; even if you fed grass, he could squeeze out milk as precious as gold.

He decided to fire Charles Ferguson immediately after the meeting, since the Paris company's performance was a complete mess and there were plenty of excuses.

At this point, Nikola Tesla drew three more sets of coils in the blank space on the blackboard, waving the chalk like a conductor:

"If a single alternating current is a monotonous pulse, then a two-phase current is a duet. And a three-phase current is a grand symphony."

He marked the phase on each coil: "Imagine three coils, 120 degrees apart, each carrying a three-phase current. The combined magnetic field is no longer just rotating—"

It maintains a constant intensity, like a perfect North Star, rotating at a uniform speed in space. This is the rhythm of nature, the way the stars move!

This should also be the way we transmit electricity!

Finally, Nikola Tesla drew a simple diagram—generator, transmission line, transformer, user.

"Gentlemen, by using three wires to transmit three-phase current, the voltage can be increased at the generator end to reduce losses, and the voltage can be decreased at the user end to ensure safety."

All of this is accomplished through a static transformer. As long as the insulation of the incoming power line and the protection of the transformer are properly implemented, it is not much more dangerous than direct current.

His chalk eventually drew a line between the generator and the user.
"A DC system is like a taut rope, capable of transmitting power only over short distances. A multiphase AC system is like a net, capable of covering the entire continent!"

After saying all this, Tesla put down the chalk and walked back to the podium: "Gentlemen, please follow my imagination and look at this kind of future—"

Electric current surges through copper wires for hundreds of miles, illuminating city lights and powering factory machines... all thanks to the force of the rotating magnetic field mentioned earlier!
We stand at the threshold of a new era. Electricity will not merely be a tool for lighting; it will become the lifeblood of industry and the nervous system of society!
"The rotating magnetic field is a manifestation of the laws of nature. By understanding it, we can harness infinite energy!"

The meeting room was completely silent. No one spoke, no one coughed, and not even the chairs creaked.

After a few seconds, some people started clapping. The applause was sporadic, then grew louder and louder, until it became a continuous clapping.

Edison did not applaud. He sat there, his hands on the armrests of his chair, his face expressionless.

As soon as the applause stopped, someone raised their hand.

"Mr. Tesla, what is the specific transmission loss of the three-phase system you just mentioned? Do you have any measured data?"

Does a copper rotor require a permanent magnet?

"What about the starting torque? Can it start under load?"

What frequency should we use?

……

The questions are piling up. Some people are asking about technical details, some about costs, some about patent status...

Tesla answered each question calmly, sometimes drawing a few strokes on the blackboard, and sometimes just giving a verbal explanation.

The question-and-answer session lasted for more than half an hour. The meeting had far exceeded the scheduled time, but no one left or urged anyone to leave.

Finally, Thomas Edison, who had been silent all along, raised his hand.

The meeting room fell silent again, and everyone turned to look at him.

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(End of this chapter)