The answer to this question would be: frequency
The higher intensity of the stimulus, the higher frequency of the action potential will be sent. The nerve can't send a higher action potential, so it firing at higher at higher intensity instead. So when you felt an intense pain, that means the pain receptor is firing more stimulus per second compared to low or mild pain.
Electricity because most cities use electricity. and a generator would be to loud in a city
The cell actually divides in Cytokinesis.
