Nikola Tesla was a Serbian-American physicist, inventor, and entrepreneur. He played critical roles in the early development of electric power and radio. Tesla was a rival of Edison for electric power and a rival of Marconi for radio. His work on electric motors made possible the construction of the world's first large-scale AC electric power plant in 1895. The plant was driven by water and located at Niagra Falls. He had important patents for radio, although Marconi was the first to demonstrate practical radio communications. The "tesla", a unit of measurement for magnetic fields, was named after him. The tesla brand of electric vehicles was also named in his honor.

Tesla invented the Tesla coil in 1891. At that time, most people didn't have electricity in their homes. Tesla proposed that huge Tesla coils could be used to wirelessly transmit electric power for long distances. Unfortunately, the idea proved to be unsuccessful and Tesla lost a great deal of money on the venture.

A Tesla coil is a device that generates extremely high voltage. The Fleet Center coil generates about half a million volts! Compare this to the AA battery which produces only one and a half volts. The voltage at the top of the Tesla coil is sufficiently strong to break down the air and produce lightning bolts!

The Tesla coil gets its name from the tall column you see in the photo. It has a copper color because it is wrapped with about 1000 turns of fine copper wire forming a single coil from top to bottom. It is the secondary coil of a transformer. The primary coil is located at the base of the secondary below the large white plastic disc. The primary is a flat spiral which only has about 12 turns. Electric current flowing in the primary generates a magnetic field in the center which couples it to the secondary. This transformer is able to change a moderately high voltage applied to the primary into an extremely an high voltage in the secondary. The lightning bolts come from the toroid, a large metalic donut that is electrically connected to the top of the secondary coil.

Tesla coils operate at high frequency. In the Fleet Center coil the voltage changes back and forth between positive and negative about 90,000 times every second! The primary coil is part of an electrical circuit designed to resonate at that frequency. The circuit also contains a spark-gap and a source of moderately high voltage. When electricity jumps across the spark-gap, it causes the primary circuit to resonate, somewhat similar to how a bell rings when you strike it. This causes the voltage in the tall secondary coil to rise up and produce lightning from the top. The spark-gap is extremely loud and bright. It is not directly visible in the photo, but it lights up the lower section.

The Fleet Tesla coil was built by Dan Grant and donated to the Fleet Center in 2018.