How many windings does a functional transformer require?

• A. One
• B. Two
• C. Three
• D. Four

Answer: (B)

Transformers transfer energy through mutual induction between windings on a common magnetic core. For that to happen, there must be a primary winding that creates a changing magnetic flux and a separate secondary winding where that flux induces voltage. If there were only one winding, there’s no second circuit to receive the induced voltage, so the device acts as an inductor rather than a transformer. Therefore, the minimum number of windings in a functional transformer is two: a primary and a secondary. Some designs add extra windings for additional outputs, but two is the essential count.