What is AUTO Transformer ?

AUTO Transformer is an electrical device which step up or step down automatically . This transformer is different from other type of transformer and that difference is that common transformers are magnetically coupled and electrical isolated while auto transformers are electrically coupled.

A good example of auto tranformers is in your home devices for example your emergrncy LED light charger  it uses auto transformer which is electrically coupled if you plug that light in sochet with 220v and touch any part of circuit or even LED you will feel a big shock like 220vac.