JEE Main 2015 · 10 Apr · Shift 1 · Physics Q18

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A 10V battery with internal resistance 1Ω and a 15V battery with internal resistance 0.6Ω are connected in parallel to a voltmeter (see figure). The reading in the voltmeter will be close to :

The 10 V cell with its 1 Ω internal resistance and the 15 V cell with its 0.6 Ω internal resistance in parallel (same polarity), both across a voltmeter V.

11.9 V

12.5 V

13.1 V

24.5 V

Answer and worked solution

Official answer: C

For cells in parallel:
$V=\frac{E_1/r_1+E_2/r_2}{1/r_1+1/r_2}=\frac{10+25}{1+\frac53}=\frac{35}{8/3}=13.1\text{ V}.$

Topics:EMF and internal resistance

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JEE Main 2015 · 10 Apr · Shift 1, Physics question 18