What is the function of an autotransformer?

An autotransformer operates using a single winding that acts as both the primary and secondary winding, allowing it to adjust voltage levels efficiently. This configuration enables the autotransformer to provide variable voltage outputs based on how many taps are used along the winding. The use of a single coil for both stepping up and stepping down voltage makes it distinct from other transformer types that require separate primary and secondary coils.

The choice that identifies the function of an autotransformer as adjusting voltage using a single coil tap accurately reflects its design and operation. Autotransformers can efficiently transfer electrical energy while minimizing losses because they do not require an isolated secondary winding like traditional transformers. This efficiency is particularly beneficial in applications where subtle voltage adjustments are necessary without the need for galvanic isolation or multiple outputs.