Three bulbs of 40 W 60 W and 100 W are arranged in series across the mains, Across which the potential difference is highest? Which bulb has lowest potential difference?
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Electricity class 10th
Answers
Resistance of 100Wbulb=200
2
/100=400ohms
Resistance of 60Wbulb=200
2
/60=666.67ohms
Resistance of 40Wbulb=200
2
/40=1000ohms
Therefore, total resistance in series = (400+666.67+1000)=2066.67ohms
Current in the circuit =200/2066.67=0.0967A
Therefore, actual power consumed by “40W”bulb=0.0967
2
x1000=9.35W (much lesser than any of the original)
The 40W bulb will grow the brightest as the current is constant in all three and it has the maximum resistance. But it would consume much less than 40W as the bulbs are connected in series, and voltage would be divided across all three filaments depending upon resistances.
Explanation:
You may refer to this answer. That is, the definition of the power of the bulbs (here, 40W, 60W, and 100W) are all referring to the power at a specified operational voltage, and would not be such power when they are rearranged in series. Since the resistance of the bulbs are independent of how they are arranged, their resistance should be compared using the equation P=V2/R, in which the operational voltage are the