If a 60 W light bulb at 120 V is left on in your house to prevent burglary, and the power company charges 10 cents per kilowatt-hour, how much will it cost to leave the bulb on for 30 days?
To calculate the cost of leaving the bulb on for 30 days, we need to determine the energy consumed by the bulb and then calculate the cost based on the energy usage. Here's how you can do it:
1. Find the energy consumed by the light bulb:
- The power rating of the light bulb is 60 W (watts).
- The bulb is left on for 30 days, which is equivalent to 30 * 24 = 720 hours.
- The energy consumed by the bulb can be calculated using the formula: Energy (in kilowatt-hours) = Power (in watts) * Time (in hours) / 1000.
- Substitute the given values: Energy = 60 W * 720 hours / 1000 = 43.2 kWh.
2. Calculate the cost:
- The power company charges 10 cents per kilowatt-hour (kWh).
- Multiply the energy consumption by the cost per kilowatt-hour: Cost = Energy * Cost per kilowatt-hour.
- Substitute the values: Cost = 43.2 kWh * $0.10/kWh = $4.32.
Therefore, it will cost $4.32 to leave the light bulb on for 30 days.