Detailed Instructions: You are given a concept, and a list of answers. You should generate a question about the concept that leads to the given answer(s).
Q: concept: Humphry Davy  answers:  ['He experimented with the voltaic pile decided that it was a chemical action which caused the production of electricity in electrolytic cells, and that the chemical interaction occurred between substances which had an opposite charge.']
A:
what kind of experiments did humphrey davy do?