# What is the mechanism that creates a potential between Zn and Cu when they are connected with a wire? [duplicate]

When people explain a galvanic reaction, they usually stop the explanation in the dogma that one is more reactive/electronegative/nobler then the other. But that doesn't really explain the mechanism. I mean, why there would be a electrostatic force between elements with different reactivity? What mechanism creates a potential there? Why electrons get repelled from $\ce{Zn}$ and get attracted to $\ce{Cu}$?