Question

An incandescent bulb has a power rating of 75 W but is only 5.0% efficient. How much energy is converted into light if the bulb runs for 60 h?

Answer 1

The 75 W incandescent bulb running for 60 hours will convert 0.225 kWh of energy into light, based on its 5.0% efficiency rating.

Step-by-step explanation:

The question asks how much energy is converted into light by a 75 W incandescent bulb running for 60 hours, given that the bulb is only 5.0% efficient. To calculate this, you first determine the total energy consumed by the bulb over the 60-hour period. Since power is the rate at which energy is consumed, and the bulb's power rating is 75 W, the total energy consumed is:

Energy (in watt-hours) = Power (in watts) × Time (in hours) = 75 W × 60 hours = 4500 Wh

Since only 5.0% of this energy is used to produce light, and 95% is wasted as heat, we then calculate the energy converted into light:

Energy converted into light = 5.0% of total energy = 0.05 × 4500 Wh = 225 Wh

This can also be expressed in kilowatt-hours (kWh) by dividing by 1000:

Energy converted into light = 225 Wh / 1000 = 0.225 kWh