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When electric bulbs of same power, but different marked voltage are connected in series across the power line, their brightness will be :A. directly proportional to their marked voltages directly proportional to the squares of their marked voltagesB. inversely proportional to the squares of their marked voltagesC. directly proportional to the squares of their marked voltagesD. inversely proportional to the squares of their marked voltages. |
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Answer» For a bulb, power `(P)=(V^(2))/(R)` `therefore P=(V_(1)^(2))/(R_(1))=(V_(2)^(2))/(R_(2))` `therefore R_(1)=(V_(1)^(2))/(P)` and `R_(2)=(V_(2)^(2))/(P)` The seres current through each is same. Heat `prop I^(2) Rt`. or `(H_(1))/(H_(2))=(R_(1))/(R_(2))` or `(H_(1))/(H_(2))=(V_(1)^(2))/(V_(2)^(2))` or `H propV^(2)` or Brightness `porp("voltage")^(2)`. |
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