This was a group class project by the students in my 4th year apprenticeship class. Every year I gave Nikola Tesla a plug since I always found it unfair that the creator of every AC electric motor that we use today, plus all of the other inventions i.e. radio, radar, x-rays, blade-less turbines etc. went unnoticed while lesser inventors like Thomas Edison literally stole the spotlight. I was a little hesitant to build one since in the past it was difficult to find construction information, but it was the Internet to the rescue. After a lot of research and experimentation we came up with our final design. The primary coil was #8 copper ground wire wrapped around a plastic bucket, and the secondary was a six-inch PVC pipe with 1000 turns of #22 gauge wire. We used a neon sign transformer to feed the resonant circuit at 15,000 volts. I estimated the final voltage output at 750,000 volts at 50,000 Hertz.
In the photo you can see a student (right) holding a florescent lamp which is in no way connected to the circuit itself, but lighting because of the electricity flowing through the air, and another student (left) holding a copper rod drawing an arc from the antenna. Even though the charge was 750 kV, the shock was barely felt because the discharge was in the micro amps, and because the high frequency increased the "skin effect" which is the tendency for electrons to migrate closer to the surface of a conductor. The higher the frequency the greater the effect, so at 50,000 Hertz, most of the electrons were traveling over the surface of the person and not through him. All this knowledge still didn't comfort me when I was the first one to poke a rod next to the antenna.
Tesla's original concept was to build a large Coil to transmit electricity wirelessly though the air to receiving coils elsewhere across the earth. In Tesla's final design the Earth itself was the capacitor and the ionosphere was the return path for the current. All one needed was a receiving coil and you could have wireless power anywhere in the world you went. Cars wouldn't need batteries, your cordless drills would never need recharging, no more ugly transmission lines criss crossing the country, there was only one fly in the ointment: How do you charge people for the electricity. Tesla's dream of wireless transmission of power (and communications) ended when funding for the project was discontinued after the Wardencliff tower was almost completed.
In the photo you can see a student (right) holding a florescent lamp which is in no way connected to the circuit itself, but lighting because of the electricity flowing through the air, and another student (left) holding a copper rod drawing an arc from the antenna. Even though the charge was 750 kV, the shock was barely felt because the discharge was in the micro amps, and because the high frequency increased the "skin effect" which is the tendency for electrons to migrate closer to the surface of a conductor. The higher the frequency the greater the effect, so at 50,000 Hertz, most of the electrons were traveling over the surface of the person and not through him. All this knowledge still didn't comfort me when I was the first one to poke a rod next to the antenna.
Tesla's original concept was to build a large Coil to transmit electricity wirelessly though the air to receiving coils elsewhere across the earth. In Tesla's final design the Earth itself was the capacitor and the ionosphere was the return path for the current. All one needed was a receiving coil and you could have wireless power anywhere in the world you went. Cars wouldn't need batteries, your cordless drills would never need recharging, no more ugly transmission lines criss crossing the country, there was only one fly in the ointment: How do you charge people for the electricity. Tesla's dream of wireless transmission of power (and communications) ended when funding for the project was discontinued after the Wardencliff tower was almost completed.
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