In a step-down transformer, which statement describes the primary winding?

• A. The winding connected to the load.
• B. The winding with fewer turns than the secondary.
• C. The winding with more turns than the secondary.
• D. The winding that carries no current.

Answer: (C)

In a transformer, the voltage you get on the secondary is set by the turns ratio between the windings. In a step-down design, the primary winding—the one connected to the input source—has more turns than the secondary winding that delivers power to the load. Because Vp/Vs = Np/Ns, a larger Np relative to Ns means Vs is smaller than Vp, so the primary is the winding with more turns than the secondary.

That’s why the statement describing the primary as having more turns than the secondary is the best choice. The winding connected to the load is the secondary, not the primary; a winding with fewer turns than the secondary would not describe the primary in a step-down; and a winding carrying no current would only occur if the circuit were open or unloaded, not during normal operation.