What type of transformer has one coil and varies both the current and voltage?

What type of transformer has one coil and varies both the current and voltage?

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

Answer: (C)

An autotransformer is a type of transformer that has a single coil that functions as both the primary and secondary winding. This design allows the autotransformer to provide variable voltage output while also adjusting the current in response to changes in load. The winding is tapped at different points to achieve various voltage levels, facilitating efficient voltage regulation and current transformation within the same coil.

In contrast, step-up and step-down transformers require two distinct coils to achieve their respective functions of increasing or decreasing voltage. A high-voltage transformer typically refers to a transformer designed specifically to produce high voltage outputs, but it does not have the capability of varying both voltage and current like an autotransformer can. The unique structure and operational flexibility make the autotransformer essential in applications where variable voltage output is needed, enhancing its utility in radiography and other fields.