To calculate the amount of electrical energy that is converted into radiant energy (light) by a 60 W light bulb that operates for 8 hours, you can follow these steps:
- Calculate the total electrical energy consumed by the light bulb in kilowatt-hours (kWh).
The power of the light bulb is 60 W, which we need to convert to kilowatts: \[ \text{Power in kW} = \frac{60 , \text{W}}{1000} = 0.06 , \text{kW} \]
Next, calculate the total energy consumed over 8 hours: \[ \text{Energy (kWh)} = \text{Power (kW)} \times \text{Time (h)} = 0.06 , \text{kW} \times 8 , \text{h} = 0.48 , \text{kWh} \]
- Calculate the amount of radiant energy produced, considering that the bulb is only 15% efficient.
Efficiency is expressed as a fraction (or percentage). Given that the bulb is 15% efficient, the energy converted into light (radiant energy) can be calculated as: \[ \text{Radiant Energy} = \text{Total Energy} \times \text{Efficiency} \] \[ \text{Radiant Energy} = 0.48 , \text{kWh} \times 0.15 = 0.072 , \text{kWh} \]
- Convert the radiant energy into a more common unit, if needed. In this case, we can keep it in kWh, or convert it to joules if necessary: \[ 1 , \text{kWh} = 3.6 \times 10^6 , \text{J} \] \[ \text{Radiant Energy in joules} = 0.072 , \text{kWh} \times 3.6 \times 10^6 , \text{J/kWh} = 259200 , \text{J} \]
Thus, the electrical energy converted into radiant energy is approximately 0.072 kWh or 259,200 J.
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