if i understood this correctly, the determination of voltage for a specific voltaic (gallvanic) cell is determined only by the chemical correlation between the two metals. is this true? for an example , if i use iron instead of zinc in the example from wikipedia, i will get a different voltage?
The voltage of a galvanic cell is the sum of the voltages of the "half cells",
wich can (not must!) be made from a metal and a solution around that "electrode".
Both the metal (or what else is there as "active" material) and the solutions ("electrolyte")
quality and concentration determine the voltage of this "electrode".
PS Be aware that the popular use of "electrodes" (up to physics textbooks!) is wrong. The carbon rod in a Zink/"carbon" cell is not an electrode at all. This is a contact material able to withstand the corrosive environment. The electrode is a mass of manganese dioxide. The latter then is "explained" as "depolarisator", a theory obsolete (and known to be wrong) since Nernsts law was published more than 100 years ago.