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# Two Exactly Similar Electric Lamps Are Arranged (I) in Parallel, and (Ii) in Series. If the Parallel and Series Combination of Lamps Are Connected to 220 V Supply Line One by One, What Will Be the Ratio of Electric Power Consumed by Them? - CBSE Class 10 - Science

ConceptResistance of a System of Resistors - Resistors in Parallel

#### Question

Two exactly similar electric lamps are arranged (i) in parallel, and (ii) in series. If the parallel and series combination of lamps are connected to 220 V supply line one by one, what will be the ratio of electric power consumed by them?

#### Solution

Let R be the resistance of the lamp and V be the potential difference applied.

In a series connection:
Net resistance of the circuit, R1 = R + R = 2R
Power drawn, P1 = V2/R1 = V2/2R
In a parallel connection:
Net resistance of the circuit, R2 will be:

1/R_2=1/R+1/R=2/R or R_2=R/2

Power drawn, P2 = V2/R2 = 2V2/R
Therefore, P2:P1 = 4:1

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Solution Two Exactly Similar Electric Lamps Are Arranged (I) in Parallel, and (Ii) in Series. If the Parallel and Series Combination of Lamps Are Connected to 220 V Supply Line One by One, What Will Be the Ratio of Electric Power Consumed by Them? Concept: Resistance of a System of Resistors - Resistors in Parallel.
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