An Auto-transformer (which has only one winding) may be used as a ______ .

• A. Step-Down Transformer
• B. Step-Up Transformer
• C. Both Step-Up and Step-Down transformer
• D. None of these

Answer: (C)

Step up transformer increases voltage level (decreases secondary current).
Step down transformer decreases voltage level (increases secondary current).

In normal operation of transformer power, flux and frequency remain same (or almost same) at input and output.