alleryA cell of emf ε and internal resistance r is connected to an external resistance R. The current is:
AI = ε / (R + r)
BI = ε / R alone
CI = ε R / r ratio
DI = ε − I·r drop
Answer & Solution
Correct answer: A. I = ε / (R + r)
1. Total resistance in the loop = R + r.
2. Kirchhoff's voltage law: ε = I(R + r) ⇒ I = ε/(R + r).
3. Terminal voltage V = ε − I r = ε R / (R + r).
_Source: syllabus Physics Ch 3 §3.8 EMF and Internal Resistance_
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