General exam question G5C01
Subelement G5, ELECTRICAL PRINCIPLES· Group G5C
What causes a voltage to appear across the secondary winding of a transformer when an AC voltage source is connected across its primary winding?
- A.Capacitive coupling
- B.Displacement current coupling
- C.Mutual inductance (correct answer)
- D.Mutual capacitance
WhyA voltage appears across a transformer's secondary winding because of mutual inductance between the primary and secondary windings. An AC current flowing in a transformer's primary winding creates a changing magnetic field that links through the transformer's core into the secondary winding, and that shared, changing magnetic field, mutual inductance, is what induces a voltage in the secondary, answer C. Transformers couple energy magnetically, not through the electric-field mechanisms of capacitive or displacement-current coupling, and "mutual capacitance" isn't the physical process at work here, so A, B, and D don't describe how a transformer actually operates.
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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