The Physics behind the Current War: Edison, Tesla, & Westinghouse (AC vs. DC)

In the late 1800s there was a battle between different types of electricity, alternating and direct, that was called the war of the currents, (now a major motion picture starting my boyfriend Benedict Cumberbatch).  There are thousands of videos about this conflict but this is the first, as far as I know, that covers the actual Physics of their debate as well as the crazy horse-killing history. 

Table of Contents

Alternating Current

How a Transformer Works

The Westinghouse Electric Company

Wrong Use of AC

Tesla’s AC

Downfall of Edison

Alternating Current

One day in the spring of 1885, a 38-year-old American named George Westinghouse read an article that changed his life.  It was about something called Alternating Current, or AC.  Now AC wasn’t new.  In fact, it had been discovered 54 years earlier when Michael Faraday had found that moving a strong magnet into or out of a coil of wire will create (or induce) a current. 

He created the idea of magnetic fields and stated a law that if the magnetic field in a coil changes, current is induced.  That inspired a Frenchman to spin a magnet near coils of wire.  In his machine, the coils would get current that would go back and forth, or alternate.  However, at the time they thought that alternating current was useless and used brushes to force the alternating current into pulsed direct current (or DC). 

25 years later, in 1856, they removed brushes and successfully used AC to light lamps.  What made this article in 1885 different and so interesting to Westinghouse is that they mentioned adding another machine to the AC generator, a transformer, which altered the voltage and the current after it had been created. 

How a Transformer Works

To understand how a transformer works I need to take a step back and talk about voltage and current, which are not the same thing.  Current is how much charge is moving in a wire over time: think of water running through a faucet.  Voltage is how much electromotive force there is behind it; think of the water pressure in your faucet. 

A battery has the same constant voltage whether it is in a circuit or on the shelf while the current it produces depends on the circuit it is connected to.  With AC you are making the voltage and the current not with a chemical reaction (like a battery) but by changing the magnetic field in a coil.  This changing field has a certain amount of power, which is transformed into a certain amount of oscillating current and a certain amount of oscillating voltage.  You can increase the voltage but then you decrease the current and visa-versa.

A transformer is actually a deceptively simple device, just two separate coils that are wrapped around an iron ring or bar.  Coils of wire with current in them act like a bar magnet, called an electromagnet.  Alternating current in loops of wire, therefore, act like a magnet that is constantly changing direction. 

An alternating magnetic field thus induces a current in the other coil that alternates at the same rate as the original.  If the second coil has more loops you get more voltage and less current.  If the second coil has less loops then you get less voltage and more current.  That’s it!

With transformers, you can build your power plant far away and then transform the electricity to high voltage and low current so that a lot less power will be lost to heat as it goes down the lines.  Then, near the houses, you can transform it to lower voltage and high current then use it as you wish.  And luckily for Westinghouse, Edison’s new light bulb worked just as well if the current went one direction (DC) as it did if the current jogged back and forth (AC).

The Westinghouse Electric Company

Anyway, most people at the time thought that AC was a novelty that would never work on a grand scale.  Why not?  For several reasons, first at the time, they had no motor that worked with AC to use in factories.  Second, the high voltage was incredibly dangerous if you touched them. 

Third, AC couldn’t be used with the most advanced generators at the time.  See, in 1866, at least three people including a German named Siemens (of the Siemens company)discovered generators that used self-excitations, or using electromagnets and re-routing some of the electricity produced by the generator to charge up the electromagnet. 

Before one-way valves or diodes, they couldn’t use self-excitation with AC.  So, to the engineers felt that AC was a step backwards not a step forwards. 

Despite this, Westinghouse had a vision that AC was the future.  He sent a message to a young engineer named Guido Pantaleoni who was in Italy for his father’s funeral to get patent rights to the transformer sight unseen, which he promptly did. 

Panteleoni also got several Siemens generators to bring back to the US although Siemens assured him personally that, “there was nothing whatsoever in alternating current, it was pure humbug, his [self-excitation] system had rendered alternating current useless.”  In fact, almost all of Westinghouse’s employees thought it was a bad idea and “it was only Mr. George Westinghouse’s personal will that put it through.”

By January of 1886, Westinghouse created “the Westinghouse Electric Company” with stock worth $1 million!  Meanwhile, William Stanley, a Westinghouse employee, tried a secret run of the AC system in his hometown of Great Barrington, Massachusetts.  Three months later they were almost ready to light up a local department store when the Edison people beat them to it and electrified a local mansion. 

Undeterred, a week later, Stanley electrified a store from a barn about a mile away.  They kept the details of their device secret (even as far as hiding their transformers in basements) but let it be known that they could electrify any building in town.  Soon, the Westinghouse people had four or five times more business then Edison’s people did. 

Westinghouse was ecstatic.  Edison was not.  Edison’s people begged him to move to AC but he refused as he was sure that AC was shortsighted as its danger would turn people off of electricity altogether.  He wrote his friend a private note, “Just as certain as death Westinghouse will kill a customer within six months.” 

The next year, Edison wrote an 84 page “Warning from the Edison Electric Light Company,” saying, “It is a matter of fact that any system employing high pressure, i.e. 500 to 2,000 Volts jeopardizes life,” he railed that Westinghouse’s AC system was cheap but deadly and declared that they “ought to unite in a war of extermination against cheapness that involves inefficiency and danger.” 

This was not a misplaced fear; high-powered electricity was a new toy and many companies were putting wires willy-nilly with little interest in public safety.  New York, in particular, was blanketed in wires from telegraph, telephone and lighting companies although Edison insisted on burying his wires underground. In 1888, after a terrible snowstorm damaged many of the wires, there was a series of deaths attributed to high voltage wires. 

Wrong Use of AC

On June 5th, 1888 a man named Harold Brown published an article about the “constant danger from sudden death” from the “damnable fatal ‘alternating’ current.” Brown was then given space in one of Edison’s laboratories where he conducted gruesome experiments killing dogs with AC current. 

The next month Brown gave his first ghastly demonstration to scientists and reporters, which caused most people to walk out “unable to endure the revolting exhibition.”  For two years, Brown repeated these horrible demonstrations on dogs and even horses (but not an elephant, that was not by Brown and unrelated to the current war). 

However, his biggest coup was in pushing for the electric chair, with AC current of course.  On August 6, 1890 a murderer named William Kemmler was the first man sentenced to death by electrocution (in an action that Edison wanted to call “Westinghoused”).  Suffice it to say that it did not go well.  The only silver lining was that Kemmler’s disturbing demise ruined Brown’s reputation and he quietly slinked away from public life, and Edison distanced himself from Brown and pretended to have never supported him.

Tesla’s AC

Meanwhile, a brilliant but quirky former employee of Edison’s named Nikola Tesla had invented a new type of AC, and a corresponding AC motor.  What was different about Tesla’s design was it was actually multiple AC systems in one.  Recall that when a coil of wire passes by an electromagnet it gets current that goes back and forth (AC). 

Tesla’s idea was to use multiple coils of wire, so that the coils will gain the same current at the same frequency but at different peak times.  This is called polyphase current.  If that same current went into an artfully designed motor, the changing currents would continuously push the coils within a magnet and make it spin at a constant speed. 

Tesla determined that his motor worked best at 60 cycles per second (or what we now call 60 Hz). Westinghouse was impressed with this to say the least.  Years later he supposedly told Tesla, “your polyphase system is the greatest discovery in the field of electricity.”  In 1888, while Brown was killing dogs, Westinghouse paid Tesla and his company $70,000 in cash and notes, plus $2.50 per horsepower on every Tesla motor from then on. 

In 1891, there was a stock market crash and Westinghouse was in large financial trouble.  He went to Tesla and begged him to give up his future profit on motors pleading, “your decision, determines the fate of the Westinghouse Company”.  Tesla magnanimously tore up the contract!  

Westinghouse still wasn’t out of trouble though.  He was still in legal disputes with Edison over the light bulb and was being sued for patent violations for a whopping one billion dollars!  That’s billion with a B, in the late 1800s.

Downfall of Edison

This brings us to J. P Morgan.  Morgan, like everyone involved in electricity, had been watching the success of the AC systems, which Edison stubbornly refused to use or accept.  He orchestrated a coup: merging Edison’s company with another, firing Edison from his own company, and even removing Edison’s name from his own company! 

From that time on instead of “Edison’s General Electric” it was plain “General Electric” or GE.  Edison pretended that he had moved on, saying “I cannot waste my time over electric-lighting matters, for they are old” but truthfully he was heartbroken. 

Edison’s secretary said that, “I know something had died in Edison’s heart, he had a deep-seated, enduring pride in his name.  And that name had been violated, torn from the title of the great industry created by his genius through years of intense planning and unremitting toil.”  From then on even GE used alternating current and the lawsuits abated, the war of the currents was over.

Two years later there was the Colombian Exposition in Chicago.  This fair was mind-bogglingly enormous, covering 600 acres with over 200 new buildings, with a total of twenty-seven million visitors.  And Westinghouse lit it with AC light at Tesla’s 60 Hz.  At the fair, Tesla gave demonstrations to the adoring crowds of something brand new, wireless electricity, which was to make him a superstar, for a while! 

However, in order to talk about Tesla and wireless I need to take a step back and talk about the connections between light and electricity and how that led to radio and wireless. And that all started in 1845, when an undergraduate asked Michael Faraday if he could turn light with magnets.  How Faraday dreamed that light is an electromagnetic wave is next time on the secret history of electricity.

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