Galvani was the first person to demonstrate the existance of current electricity. Before that, they only knew about static electricity. This is why we name things like Galvanic cell, Galavanic current
Volta's significance is that he took scientific focus back to the right track. instead of arguing about some juice in the animal's brain that caused electrical discharges as proposed by Galvani. Volta actually said it was the chemical reaction that produced the Galvanic current. He built the voltaic pile, and that was significant as that was the first know battery at the time.
Davy simply implemented Volta's Voltaic cell and pass electricity through an aquesous solution to isolate many alkali and alkaline metal. He's signficance is mainly his implmentation of electrochemistry and he also propose if electricity is able to break down a compound then, compound must be held by electrostatic forces. Davy also was the first person to propose sacrifical anode.
Faraday, most famous for his mathematically relationship between current and rate of electrolysis. He also proposed alot of the terms that we assocaite with electrochemistry i.e. cathode and anode. I am not sure, but I assume he got most of his laws by experimental result, He was just a lab assistant. (Never know, your school's Lab Assisstant could be the next Faraday).
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