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Question
A battery of e.m.f 3.0 V supplies current through a circuit in which the resistance can be changed.
A high resistance voltmeter is connected across the battery. When the current is 1.5 A, the voltmeter reads 2.7 V. Find the internal resistance of the battery.
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Solution
ε = 3 volt
I = 1.5 A
V = 2.7 V
V = ε − Ir
r = (e-V) / I
= (3 – 2.7) / 1.5 = 0.2 ohm
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