A typical household circuit is capable of carrying 30.0 Amps of current at 120 V before the circuit breaker will trip. How many 1500-W hair dryers can run off one such circuit?
In the rush to get ready for lecture, a physics professor leaves the hair dryer described in the previous problem running and does not turn it off until he gets home 6.5 hours later. How much will this add, in dollars, to his next electric bill (assume electricity costs $0.078 per kilowatt-hr)?How many 1500-W hair dryers can run off one such circuit?
P = V*I
Solve for I if V = 120 and P = 1500.
Figure out how many times that much current goes into 30. For instance, if each hair dryer draws 5 A, then a 30 A circuit can support 30/5 = 6 hair dryers.
The energy usage in 6.5 hours in kilowatt-hr is 1.5 kW x 6.5 hours
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