Which bulb will glow brighter, a 40 Watt bulb or a 60 watt when connected in series. Why?

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scernenefmet · Accepted Answer

For the sake of simplicity, assume the bulbs are rated at 100V and that the more power a bulb consumes, the brighter it is.The bulbs are in series so the amount of current flowing through each is same. The two resistances are in series (assuming pure resistance). So      R    1    =            100      2        60    for 60 Watt bulb      R    2    =            100      2        40   for 40 Watt bulb Current drawn   I  =      V          (      R      1      +      R      2      )        =      100          [              100        2            (              1        60            +              1        40            )      ]        =  60  ×      40    100    ×  (  60  +  40  ) Power Consumer by bulb1=       I    2    R  1  =      60    2    ×            40      2              100      2        ×  (  60  +  40      )    2    ×            100      2        60    =            60      ×              40        2                    (      60      +      40      )        =  9.6 Watts Power Consumer by bulb2  =      I    2    R  2  =  40  ×            60      2              (      60      +      40              )        2              =  14.4 Watts (this is similar to the expression above) So 40 Watts bulb glow brighter. The trick is that a bulb is essentially just a resistance so             40      W              60      W       can only consume that kind of power when it is available.Like inn my assumption when connected in parallel to the AC source (100 V). Current may change voltage may change wattage may change resistance will remain invariant, ermm for the scope of this discussion alone. Find the invariant quantity and complete the tasks.

Which bulb will glow brighter, a 40 Watt bulb or a 60 watt when connected in series. Why?

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