What is the difference between an electric motor and an electric generator?

The modern DC motor was not designed as a motor. In the middle 1800s, inventor Zenobe Gramme was trying to build an electric generator which gave a very smooth output voltage. He did this by using many coils with overlapped fields. Because of it's smooth DC output, such a generator could replace large banks of batteries being used at the time. In 1873 one of his assistants accidentally connected two of his generators together. The first generator was being spun by a steam engine, and the second one unexpectedly started spinning like a motor. The "Gramme Machine" has been used ever since, under the name "DC motor" or "DC generator.  more