Thomas Edison and Nikola Tesla were pioneering inventors who changed the world with their innovations in electricity and power. Edison is best known for inventing the incandescent lightbulb, while Tesla is known for his work with alternating current. However, Edison had a secret method that he used to power his lightbulbs that truly shocked Tesla.

Edison's Direct Current vs Tesla's Alternating Current

Edison was a proponent of direct current (DC) as a means to distribute electricity. DC flows in one direction from a generation source to the load.

Tesla, on the other hand, championed the use of alternating current (AC) to transmit and distribute power. AC reverses direction at regular intervals and allows voltage to be stepped up or down using a transformer.

This difference between DC and AC emerged as the War of Currents in the late 1880s as Edison and Tesla competed to establish their electrical systems.

Edison's Secret: The Carbon Filament Lightbulb

Edison conducted over 3,000 experiments with different materials to find a suitable filament for an incandescent lightbulb.

He settled on a high-resistance carbon filament enclosed in a glass bulb containing a near vacuum. Applying DC to this filament caused it to glow and produce light.

However, producing these carbon filaments was an extremely secretive and complex process involving special bamboo and complex manufacturing techniques. Edison kept this filament fabrication method a closely guarded secret.

How the Carbon Filament Worked

Edison took advantage of the unique electrical resistance properties of carbon. When the DC current passed through the thin carbon filament, it encountered enough resistance to heat the filament to incandescence and emit light.

However, unlike metal wires, the carbon did not melt or break under these conditions. The near-vacuum environment in the bulb prevented the carbon from quickly burning up.

This gave Edison's lamps much longer operating life than earlier attempts at incandescent lighting. The carbon filament was the key innovation that made Edison's lightbulb commercially practical.

Why the Filament Fabrication Was So Important

Producing the carbon filament was extraordinarily complex. Edison tested over 6,000 plants before settling on Japanese bamboo as the raw material.

The bamboo was treated, processed and shaped into fine filaments using special machinery and techniques developed by Edison's team. Even minor variations in the filament manufacturing process greatly affected the performance and consistency of the lamps.

Keeping the filament fabrication technique confidential helped Edison maintain his competitive advantage in commercial lighting as he established DC power distribution systems.

How Tesla's AC Shocked Edison's DC System

Tesla's demonstrations of AC transformers proved they could change voltages efficiently and economically. By using very high voltages (110 - 220V) to transmit power and then stepping down to standard low voltages (100V) for indoor lighting, AC allowed electricity to be spread over much greater distances.

Edison's DC system was restricted to generating and distributing electricity only at the low voltages suitable for lighting in a small area. Transmitting DC long distances required extremely thick and expensive copper wires.

AC immediately superseded DC for commercial power distribution once these cost and capability advantages became clear. Edison's secret filament was not enough to overcome the inherent limitations of DC power transmission.

The Brilliance and Legacy of Edison and Tesla

Both Edison and Tesla made remarkable breakthroughs in electrical and lighting technology. Edison's carbon filament lightbulb enabled the widespread adoption of electric lighting. Tesla's insights into AC allowed affordable electrification over large regions.

Their contributions still live on today in the fundamental building blocks of our electrical systems and infrastructure. The 'War of Currents' between their competing visions ultimately benefited society by establishing standards still used globally over 100 years later.