alleryStart learning →A 60-W incandescent bulb is replaced by a compact fluorescent lamp of the same brightness. What is the wattage of the replacement?
A15 W
B30 W
C45 W
D60 W
Answer & Solution
Correct answer: A. 15 W
1. Fluorescent lamps are about four times as efficient as incandescent ones for the same light output.
2. So the replacement needs about a quarter of the input power.
3. A quarter of 60 W is 15 W, which is the rating of the equivalent compact fluorescent lamp.
4. It also lasts up to ten times longer, so the running cost falls further still.
5. 30 W would be the answer if the efficiency gain were only a factor of two.
_Source: OpenStax College Physics (CC BY 4.0), Ch 20 "Electric Current, Resistance, and Ohm's Law", section The Cost of Electricity_
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