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Two lamps rated 25 W - 220 V and 100 W - 220 V are connected to 220 V supply. Calculate the powers consumed by the lamps.


Given, 
First lamp = 25 W - 220 V 
Second lamp = 100 W - 220 V 
Voltage (V) = 220 V 
Power Consumed (P) = ?

Now, to calculate the resistance
For first lamp,   P1=25W 
Voltage (V1)=220V 
R1=V21P1=220225=1936Ω                                                   [∵ P=V2R]

For second lamp,   P2=100W 
Voltage (V2)=220V 
R2=V22P2=2202100=484Ω 

If two lamps are connected in series and joined to 220 V mains, then the current  in the circuit (I) is calculated as,
I=VR1+R2=2201936+484=0.091A

Finally, 
Power consumed by the first lamp = I2R1=(0.091)21936=16W 
Power consumed by the second lamp = I2R2=(0.091)2484=4W

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