Extra exam question E6F08
Subelement E6, CIRCUIT COMPONENTS· Group E6F
Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?
- A.Optoisolators provide a low-impedance link between a control circuit and a power circuit
- B.Optoisolators provide impedance matching between the control circuit and power circuit
- C.Optoisolators provide an electrical isolation between a control circuit and the circuit being switched (correct answer)
- D.Optoisolators eliminate the effects of reflected light in the control circuit
WhyOptoisolators are used with solid-state circuits controlling 120 VAC circuits to provide electrical isolation between the control circuit and the circuit being switched. Optoisolators are used alongside solid-state circuits that control 120 VAC loads specifically to provide electrical isolation, keeping the low-voltage control circuit physically and electrically separated from the higher, potentially dangerous voltage being switched, since the only connection between the two sides is a beam of light, answer C. They don't provide a low-impedance link or impedance matching between the circuits, and they aren't there to eliminate reflected light effects, electrical isolation for safety is the real reason they're used here.
Published 2026-08-28 · Last updated 2026-08-28 · Question text is verbatim from the 2024-2028 NCVEC Element 4 pool (public domain); the explanation above is original writing, see our methodology.
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