Transformer

A transformer is used to change one a.c voltage into another.
Transformers will only work with ac. The number of turns on both the primary and secondary coils affects the output voltage of the transformer.
If the number of turns on the primary is greater than that on the secondary then the voltage on the secondary will be less than that on the primary. If there are more turns on the secondary the output voltage will be larger.

If the secondary voltage is less than the primary voltage the transformer is known as a STEP-DOWN transformer.
If the secondary voltage is greater than the primary voltage the transformer is known as a STEP-UP transformer

Secondary voltage (V_S)/Primary voltage (V_P) = Secondary turns (n_S)/Primary turns (n_P)

Secondary voltage (V_S) = V_P x [n_S/n_P]