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Question 31639
JEE Physics · Hard

Current Electricity: Cell Efficiency MCQ

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Cell EfficiencyHardQuestion 31639

Question

Efficiency of a cell delivering current to external resistance R (internal resistance r) is:
  1. A
    r/(R+r)
  2. B
    R/(R+r)
    Correct
  3. C
    E/(E+Ir)
  4. D
    r/R

Correct answer

R/(R+r)

Explanation

Efficiency η = P_ext/P_total = I²R/(I²(R+r)) = R/(R+r). For high efficiency, use cells with small internal resistance or large external loads.

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