Two batteries of emf 18 V with internal resistance 2 Ω and emf 12 V with internal resistance 1 Ω are connected with opposing polarities as shown. Voltmeter reading will be: [Diagram: Image]
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Two batteries of emf 18 V with internal resistance 2 Ω and emf 12 V with internal resistance 1 Ω are connected with opposing polarities as shown. Voltmeter reading will be: [Diagram: Image]

G1 Physics · Accepted Answer

Step 1: Opposing emfs drive internal circulating current I = (18−12)/(2+1) = 2 A. Step 2: Voltage of the 18 V battery when delivering current: V = 18−(2×2) = 14 V. Step 3: Across the 12 V cell when charging: V = 12+2×1 = 14 V. Hence voltmeter reads 14 V.