Adevice that increases or decreases voltage is called a (n)
a. alternator.
b. transformer.
c. generator.
d. turbine.

Transformer.

Explanation:

A transformer is an electrical device that has the ability to transfer the electric energy between the two circuits. The energy can be transferred by without the metallic connection.

The transformer used to decrease or increase the voltage between the two circuits. Transformers are also used to couple the stage of the signal processing circuits.

Thus, the correct answer is option (B).