How many 1200-watt hair dryers can be operated by a 120V circuit protected by a 20 amp circuit breaker?

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Prepare for the PMMI Industrial Electricity Test with quizzes featuring flashcards and multiple-choice questions. Each answer is explained with hints to ensure a thorough understanding. Gear up to excel in your exam!

Multiple Choice

How many 1200-watt hair dryers can be operated by a 120V circuit protected by a 20 amp circuit breaker?

Explanation:
The main idea is how current, voltage, and power relate on a circuit. A device that uses 1200 watts at 120 volts draws current I = P / V = 1200 / 120 = 10 amperes. A 20-amp circuit breaker can supply up to 20 amperes, so you can run up to two of these dryers at the same time (2 × 10 A = 20 A). Three would require 30 amperes, which would trip the breaker. In practice, startup surges can affect current, but the straightforward calculation shows two is the limit for this setup.

The main idea is how current, voltage, and power relate on a circuit. A device that uses 1200 watts at 120 volts draws current I = P / V = 1200 / 120 = 10 amperes. A 20-amp circuit breaker can supply up to 20 amperes, so you can run up to two of these dryers at the same time (2 × 10 A = 20 A). Three would require 30 amperes, which would trip the breaker. In practice, startup surges can affect current, but the straightforward calculation shows two is the limit for this setup.

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