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Question:

In the given circuit, an ideal voltmeter connected across the 10Ω resistance reads 2V. The internal resistance, r, of each cell is:

1.5Ω

1Ω

0Ω

0.5Ω

Solution:

The correct option is D 0.5Ω
Req=15×10/25+2+2r=8+2r
i=3/8+2r
2=iReq=3/(8+2r)×6/(6+4r)=18
→r=0.5Ω