Which of the following is NOT present in an auto transformer?

The correct answer is option 3): (Conductive isolation between primary and secondary)

Concept:

• An autotransformer is an electrical transformer with only one winding.
• The "auto" prefix refers to the single coil acting alone, not to any automatic mechanism.
• In an autotransformer, portions of the same winding act as both the primary winding and secondary serpentine sides of the transformer.

• An Autotransformer is a variable output voltage transformer.
• An autotransformer is a kind of transformer where primary and secondary share the same common single winding. So option 3 is wrong.
• In an autotransformer, energy transforms taking place through both conduction and induction. It works as a variable transformer.
• This type of variable autotransformer is generally used in laboratories and science labs in schools and colleges. It is commonly known as Variac.