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JEE Main 2022 · 24 Jun · Shift 1, Physics question 33

Two identical cells each of emf 1.5 V are connected in parallel across a parallel combination of two resistors each of resistance 20 Ω20\ \Omega. A voltmeter connected in the circuit measures 1.2 V. The internal resistance of each cell is :

Choose one option
Answer and worked solution

Official answer: C

Equivalent cell. Two identical cells in parallel act as emf 1.5 V with internal resistance r/2r/2.

External resistance. 20∥20=10 Ω20\parallel20=10\ \Omega.

Terminal voltage. 1.2=1.5×1010+r/21.2=\dfrac{1.5\times10}{10+r/2} gives 10+r2=12.510+\dfrac r2=12.5, so r=5 Ωr=5\ \Omega.

(C)

Topics:EMF and internal resistanceSeries and parallel resistors
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