What is the purpose of a transformer? transformers adjust overall circuit resistance. transformers change the frequency of an oscillating current. transformers change the voltage in a circuit. transformers store charge.

Transformers change the voltage in a circuit.

Explanation:

A transformer is an electrical device that changes electrical signal (voltage or current) from one level to another. Voltage transformer is an electrical device that changes alternating current (ac) voltage at one voltage level to another voltage level through the action of electromagnetic induction(Faraday's Principle). A transformer consists of two or more coils of wire wrapped around a common ferromagnetic  core. These coils are (usually) not directly connected. The only connection between the coils is the common magnetic flux present within the core. There are two major classes of transformers. Step-Up Transformer and Step-Down Transformers. Step-Up transformers are designed to increase ac voltage level while Step-Down transformers are designed to reduce ac voltage level.

see earlier