Updated: Dec 9, 2025 | Source: 2024-2028 Question Pool | Topic: E6F
E6F08E6F

Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits?

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Deep Dive: E6F08

The correct answer is C: Optoisolators provide an electrical isolation between a control circuit and the circuit being switched. Why are optoisolators often used in conjunction with solid-state circuits that control 120 VAC circuits is that optoisolators provide an electrical isolation between a control circuit and the circuit being switched. Optoisolators provide safety isolation. For amateur radio operators, this is important for safety. Understanding this helps when designing control circuits.

Why Other Answers Are Wrong

Option A: Incorrect. Optoisolators providing low-impedance link isn't the reason - optoisolators provide isolation. Low-impedance link isn't the reason. Option B: Incorrect. Optoisolators providing impedance matching isn't the reason - optoisolators provide isolation. Impedance matching isn't the reason. Option D: Incorrect. Optoisolators eliminating reflected light effects isn't the reason - optoisolators provide isolation. Reflected light isn't the reason.

Exam Tip

Optoisolators with 120VAC control = provide electrical isolation between control and switched circuit. Think 'O'ptoisolator = 'I'solation. Optoisolators provide safety isolation. Not low-impedance link, not impedance matching, not reflected light - just electrical isolation.

Memory Aid

Optoisolators with 120VAC control = provide electrical isolation between control and switched circuit. Think 'O'ptoisolator = 'I'solation. Optoisolators provide safety isolation. Important for safety.

Real-World Example

Optoisolators with solid-state circuits controlling 120 VAC: They're used because optoisolators provide an electrical isolation between a control circuit and the circuit being switched. This protects the control circuit from high voltage. This is the reason - electrical isolation.

Source & Coverage

Question Pool: 2024-2028 Question Pool

Subelement: E6F

Reference: 2024-2028 Question Pool · E6 - Circuit Components

Key Concepts

Optoisolators Used in conjunction with Solid-state circuits Control 120 VAC circuits Electrical isolation

Verified Content

Question from the official FCC Extra Class pool. Explanation reviewed by licensed amateur radio operators and mapped to the E6F topic.