General exam question G5C05
Subelement G5, ELECTRICAL PRINCIPLES· Group G5C
Why is the primary winding wire of a voltage step-up transformer usually a larger size than that of the secondary winding?
- A.To improve the coupling between the primary and secondary
- B.To accommodate the higher current of the primary (correct answer)
- C.To prevent parasitic oscillations due to resistive losses in the primary
- D.To ensure that the volume of the primary winding is equal to the volume of the secondary winding
WhyThe primary winding of a voltage step-up transformer usually uses larger wire than the secondary to accommodate the primary's higher current. A step-up transformer's primary carries the higher current side of the power transfer (since power is roughly conserved and the primary is at the lower voltage), and thicker wire is needed to carry that larger current without excessive resistive loss or heating, so the primary winding uses larger-gauge wire, answer B. It isn't about improving magnetic coupling, preventing parasitic oscillation, or matching winding volumes, those aren't the reason for the wire-gauge difference.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2023-2027 NCVEC Element 3 pool (public domain); the explanation above is original writing, see our methodology.
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