A transformer works by passing a current in a primary coil that produces a magnetic field that grows and collapses. This pulsing magnetic field induces a current in a secondary wire coil. The transformation of the voltage comes from the difference in the Blank______. Multiple choice question. number of loops between the primary and secondary coils metal used for the primary and secondary coils length of time between the growth and collapse of the magnetic field direction of the loops in the primary and secondary coils