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Examoogle • User • info@examoogle.com • EE-2024-8821
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What is the efficiency of fluorescent tube?
70 Lumen/volt
170 Lumen/volt
17 Lumen/volt
700 Lumen/volt
70 Lumen/volt
Quick Summary: The luminous efficiency of a fluorescent tube is a measure of how effectively it converts electrical energy into visible light, expressed in lumens per watt (lm/W). For a standard fluorescent tube, this efficiency typically ranges between 60 to 80 lumens/watt depending on the lamp length and type.
The luminous efficiency of a fluorescent tube is a measure of how effectively it converts electrical energy into visible light, expressed in lumens per watt (lm/W). For a standard fluorescent tube, this efficiency typically ranges between 60 to 80 lumens/watt depending on the lamp length and type.
η=PΦ — where η is efficiency, Φ is flux in lumens, and P is power in watts.
The tube operates via gas discharge where mercury vapor emits ultraviolet radiation when excited by an electric arc. This UV light hits a phosphor coating inside the tube, which absorbs the UV radiation and re-emits it as visible light through the process of fluorescence. The efficiency is determined by the ratio of total luminous flux emitted to the total power input.
Fluorescent lamps are significantly more efficient than incandescent bulbs.
Luminous efficiency is highly dependent on the ballast type (magnetic vs electronic).
Average rated efficiency for standard T8/T12 tubes is approximately 70-80 lm/W.
High luminous efficacy compared to incandescent sources.
Long operational life (typically 10,000 to 20,000 hours).
Low surface brightness reduces glare.
Requires a ballast for starting and current limiting.
Contains mercury, requiring careful disposal.
Performance degrades with frequent switching.
Office and commercial lighting.
Industrial floor lighting.
Residential interior lighting.
Note: The original question incorrectly labeled the unit as Lumen/volt. The physical unit for luminous efficiency is Lumen/Watt (lm/W).
Incandescent lamps typically provide 10-15 lm/W, whereas fluorescent tubes offer 60-100 lm/W.
A is correct — The luminous efficiency of a standard fluorescent tube is approximately 70 Lumens per Watt (lm/W).
In exams, always look at the units carefully; efficiency is always expressed in terms of output (Lumens) per unit input (Watts), never per Volt.