Question

An electric machine which can change the line of voltage of electric supply

Answer 1

An electric machine which can change the line of voltage and electric supply I think voltage regulator

Answer 2

A transformer is a static device that converts alternating current from one voltage level to another level (higher or lower), or to the same level, without changing the frequency. A transformer transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils.