Final answer:
A house must have at least one dedicated 20-amp circuit for bathroom lighting fixtures. Electrical devices can trip a circuit breaker if their combined current exceeds the breaker's capacity. The cost of power consumption at the given conditions for a month would be $1036.80.
Step-by-step explanation:
The fewest number of 120-volt, 20-amp branch circuits permitted to be installed in a house for supplying power to the lighting fixtures in the bathroom is one. Electrical codes typically require at least one dedicated 20-amp circuit for bathroom receptacles. Appliances and lighting fixtures have different power and current demands, which is evident from the various examples given, such as an 1800-W toaster drawing 15 A, and circuit breakers are intended to protect against overcurrent situations that can lead to electrical fires.
When considering the power consumption of a 100-ampere house operating at 80% capacity, the power consumption can be calculated using the formula P = VI, where 'P' is power, 'V' is voltage, and 'I' is current. Thus, at 120 volts, the power consumed is 0.8 × 100 A × 120 V = 9600 watts or 9.6 kilowatts. Over a month, assuming 30 days, this accumulates to 9.6 kW × 24 hours/day × 30 days = 6912 kWh. At a rate of $0.15 per kWh, the cost would be 6912 kWh × $0.15/kWh = $1036.80.
Circuit breakers are rated in amperes to prevent electrical overloads. Devices such as a 120-V immersion heater, incandescent lamps, and space heaters can draw significant currents that could potentially trip circuit breakers if their combined current exceeds the breaker's rating, such as a 15-amp breaker.