Question

The current in a 120 V reading lamp is 1.5 A . If the cost of electrical energy is $0.075 per kilowatt-hour, how much does it cost to operate the light for an hour? Express your answer using two significant figures.

Answer 1

To calculate the cost of operating the light for an hour, multiply the power by the time and then multiply by the cost per kilowatt-hour. The cost to operate the light for an hour is $0.01.

Step-by-step explanation:

To calculate the cost of operating the light for an hour, we need to find the electrical energy consumed. The given current is 1.5 A and the voltage is 120 V. Since power (P) is equal to voltage (V) multiplied by current (I), we can calculate the power as P = 120 V * 1.5 A = 180 W. Next, we convert the power to kilowatts (kW) by dividing by 1000, so 180 W * (1 kW / 1000 W) = 0.18 kW.

Now, we can calculate the energy consumed in kilowatt-hours (kWh) by multiplying the power by the time in hours. Since we want to find the cost for operating the light for one hour, the time is 1 hour.

Therefore, the energy consumed is 0.18 kWh * 1 hour = 0.18 kWh. Finally, we can calculate the cost by multiplying the energy consumed by the cost per kilowatt-hour, which is $0.075. So the cost to operate the light for an hour is 0.18 kWh * $0.075/kWh = $0.0135, which rounds to $0.01.