In 1875, Tesla began studying electrical engineering at the Polytechnic Institute in Graz, Austria. Again, with obsessive effort that permitted only study, he excelled. In Graz, Tesla was able to observe the new Gramme machine which generated direct current electricity using electromagnets and could also be reversed to operate as an electricity-driven motor. The demonstration planted an intuitive seed in Tesla's brain. Why was it necessary to go to such lengths to convert the alternating (AC) current produced by the dynamo to direct (DC) current? Why not leave the current AC and run the motor that way?
The electrical standard at that time was DC, the same mode produced by a battery the mode that everyone was used to and accepted. To even imagine usable alternating current was visionary. Tesla's strong instincts told him this was possible but at that time, in spite of his visualization efforts and the mental gymnastics of picturing many operating dynamo models, he failed to find the solution to this nagging problem.