How it works
A transformer transfers electrical energy between two or more separate coils of wire through electromagnetic induction. When an alternating current (AC) flows through the primary coil, it creates a fluctuating magnetic field that induces a corresponding voltage in the secondary coil.
Transformers are used to step-up (increase) or step-down (decrease) AC voltages. The ratio of the input voltage to the output voltage is determined entirely by the ratio of the number of turns of wire in each coil. Note: Transformers only work with AC or fluctuating signals; they block steady DC voltages entirely.