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For his science fair project, John decided to experiment with renewable energy sources. He hoped that his work will solve all of our energy problems. He decided to power a generator with an electric motor. He thought once the generator was up to speed, he could just flip a switch and the generator could supply the electricity that powered the electric motor. John was for sure he made a historical discovery, he found an alternative to fossil fuels. His energy source was purely renewable. Why did his experiment fail once he put it to the test?

An electric generator does not actually create energy. It just converts mechanical energy into electrical energy. The motor just converts electrical energy into mechanical energy. However, some of this energy is converted to heat and effectively lost. So even if the generator could run the motor and the motor could turn the generator, with some of the energy lost as heat, there would not be enough left to keep them running and they would slow down and stop.

no energy creation happens, only conversion happens.

here only mechanical energy gets converted to electrical

since no new energy is being created in the experiment.

law of conservation of energy