In a 120 V circuit using copper 12 AWG over 50 ft one-way with a load drawing 20 A, the approximate voltage drop is closest to:

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Study for the Low Voltage Qualification Test. Explore flashcards and multiple-choice questions with hints and explanations for each, ensuring thorough preparation!

Multiple Choice

In a 120 V circuit using copper 12 AWG over 50 ft one-way with a load drawing 20 A, the approximate voltage drop is closest to:

Explanation:
Voltage drop comes from the resistance the current encounters in the conductors. For copper 12 AWG, the resistance is about 1.588 ohms per 1000 feet. The circuit path is 50 ft one-way, so the current travels 100 ft total. That gives a resistance of (100/1000) × 1.588 ≈ 0.159 ohms. With a load drawing 20 A, the drop is V = I × R ≈ 20 × 0.159 ≈ 3.18 V, about 3.2 V. In a 120 V system, this is a small drop (~2.7%), and 3.2 V is the closest value.

Voltage drop comes from the resistance the current encounters in the conductors. For copper 12 AWG, the resistance is about 1.588 ohms per 1000 feet. The circuit path is 50 ft one-way, so the current travels 100 ft total. That gives a resistance of (100/1000) × 1.588 ≈ 0.159 ohms. With a load drawing 20 A, the drop is V = I × R ≈ 20 × 0.159 ≈ 3.18 V, about 3.2 V. In a 120 V system, this is a small drop (~2.7%), and 3.2 V is the closest value.

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