Now thirty-three years old, a rich man who had rejected marriage in favor of his devotion to science and nature, Tesla applied his genius to wider, greater endeavors. He set out to investigate the limits of electromagnetic radiation. He created electric current operating at up to 10,000 cycles per second (the U.S. standard is 60) in an effort to duplicate a light beam. He noted the advantage of high frequency current in the transformer used for electricity transmission and went on to invent the Tesla coil transformers in insulating oil baths still in use today. Tesla's experiments reached a frequency of 20,000 cycles per second at extremely high voltages. At an address to the American Institute of Electrical Engineers in May, 1891, he caused a sensation by demonstrating 100,000 volt spark discharges five inches long, plus the brightest of electric laps, from transformed alternating current.
Tesla was now a public hero, celebrated everywhere, yet still obsessed with his appetite for knowledge of all things electrical. He returned the favor of many invitations with elaborate meals for his guests followed by a laboratory show of all kinds of spellbinding, glowing, sparking, and spinning objects driven by electricity. The highlight was a demonstration in which he passed electric current through his body from head to toe, having first determined the optimum frequency and power then produced these conditions using his high-frequency dynamos and coil transformers.
Eventually accepting European invitations, Tesla took his enlightening lecture and show of amazing electrical experiments on the road. In just eight years since leaving Paris for the United States, Tesla had gone from penniless immigrant to engineer to destitute ditch digger and now to international celebrityall by the age of thirty-six. Among the innovativeand later widely adoptedinventions he demonstrated were neon and phosphorescent lamps, electronic tubes for wireless signal reception, and coil tuning principles used in radios.