A 1500 W electric heater is plugged into the outlet of a 120 V circuit that has a 20 A circuit breaker.?

You plug an electric hair dryer into the same outlet. The hair dryer has power settings of 600 W, 900 W, 1200 W, and 1500 W. You start with the hair dryer on the 600 W setting and increase the power setting until the circuit breaker trips. What power setting caused the breaker to trip?

A) 600 W

B) 900 W

C) 1200 W

D) 1500 W

I said option C.

But I don’t know whether I am correct or not. Can someone please help me.

Thank You Very Much In Advance.

1 Answer

  • In theory the 20 amp breaker will carry up to 20 amps and will trip for currents above that. (Since your loads are almost entirely resistive you can ignore power factor.) So the total power that you can draw is 2400 watts. 2400-1500=900, so B is the correct answer.

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