Which of the following is NOT a type of transformer?

• A. Step-up transformer
• B. Step-down transformer
• C. Rectifying transformer
• D. Autotransformer

Answer: (C)

A rectifying transformer is often confused with transformers due to its role in electrical circuits. However, it is important to understand that it primarily serves the purpose of converting alternating current (AC) into direct current (DC). Rectifying transformers typically integrate diodes to achieve this conversion and are not classified as a type of transformer in the traditional sense.

On the other hand, both step-up and step-down transformers are standard types of transformers used in electrical engineering for voltage regulation. Step-up transformers increase voltage, while step-down transformers decrease it. Autotransformers are another type that uses a single winding to serve as both primary and secondary, allowing for efficient voltage transformation and regulation.

By distinguishing the functions of each option, it becomes clear why "rectifying transformer" does not fit within the traditional classification of transformers and is, therefore, the correct choice.