Answer: The correct answer is "transformer".
Explanation:
Transformer: It is a device which transfers energy between two or more circuit.
It converts the voltage from low to high or high to low.
There are two types of transformers: Step-up transformer and Step-down transformer.
Step-up transformer: It is used to convert the voltage of alternating current from low voltage to high voltage.
Step-down transformer: It is used to convert the voltage of alternating current from high voltage to low voltage.
Therefore, a device that increases or decreases the voltage of alternating current is a transformer.
