Two electrical essays

THEVENIN´S theorem can be stated as follows: “With respect to any single external circuit connected to any given pair of terminals of a network, the network can be replaced by a single branch having an impedance, Z, equal to the impedance measured at these terminals looking into the network when all the network electromotive forces are made zero, and containing a single electromotive force, E0, equal to the open-circuit voltage of the network across the given pair of terminals.”