Two identical cells each of emf 1.5 V are connected in parallel across a parallel combination of two resistors each of resistance 20Ω. A voltmeter connected in the circuit measures 1.2V. The internal resistance of each cell is
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Question

Two identical cells each of emf 1.5 V are connected in parallel across a parallel combination of two resistors each of resistance 20Ω. A voltmeter connected in the circuit measures 1.2V. The internal resistance of each cell is

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G1 Physics · Accepted Answer

Treat an ideal voltmeter as open circuit and an ideal ammeter as zero resistance; for galvanometer conversion use the standard series/shunt resistance relations. The result matches C (5Ω).