hello,every one Could anyone tell me the historical order of the demodulation of these quantities? My question is how could it the el. charge been defined(ocording to the el. current?but how?were they able to measure el. currrent in that time?) thanks, PS,could u plz introduce me some books that about the history of physics ; answering such qustions like how is i.e energy defind,what caused the concept of energy...etc.