UPSC General Studies Sample Paper General Studies Sample Paper-5

  • question_answer
    With reference to CFL bulbs, consider the following statements.                       
    1. Unlike other bulbs, CFL are consumer friendly and don't pose health hazard,            
    2. The luminous efficacy of a typical CFL is 50-70 lumens per watt (1m/w) and that of a type incandescent lamp is 10-17 lm/w.                                                   
    3. The luminous efficacy of lamps is the number of lumens produced for each watt of electrical power used.                                                                            
    4. CFLs emit light from a mix of phosphorus inside the bulb each emitting one band of colour.  
    Which of the statements given above are correct?                                       

    A)  1 and 4           

    B)  2, 3 and 4          

    C)  3 and 4           

    D)  All of these   

    Correct Answer: D

    Solution :

    [d] CFL contain mercury and is an health hazard. CFL emit light from a mix of phosphorus inside the bulb, each emitting one band of colour. Every extra phosphorus added to the coating mix improves colour rendering, but decreases efficiency and increases cost. Compared to a theoretical 100% efficient lamp (680 1m/w) CFL lamps have lighting efficiency ranges of 7-10% versus 1.5-2.5% for incandescents.

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