Circuit problems

Question

1) How many 60 W light bulbs could be plugged into a 110 V circuit protected by a 15A circuit breaker?

2) At $0.15 per kW•h, how much will it cost (for electricity) for a family to prepare a dinner? They use a 1500 W microwave for 30 minutes

Answer 1

1. We know that the ampere capacity of the circuit is 15A. We also know that the circuit being used has a voltage of 110 V. Therefore we could figure out the maximum amount of power that could be produced before the current is interrupted, by plugging in the given values into the formula: Power = (Voltage)(Current) --> P= VI.

P= VI ---> P = (110)(15) = 1650 W

maximum power supported is 1650W. Each bulb is a 60W bulb.

So by dividing 1650W by 60W, we get 27.5. In this case we would round down, because we don't want the current to be interrupted. Therefore, 27 bulbs can be supported by this circuit.

2. To find the cost, we would use this formula:

Cost = (power rating of device in kW•h)(number of hours device is used)(cost per kW•h)

substituting with our given values:

Cost = (1.5 kW)(0.5 hours)($0.15 per kW•h)

Cost =$0.1125