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JAMB Physics 2000 Question 40

Question 40

Current Electricity

A cell of internal resistance 1 Ω supplies current to an external resistor of 3 Ω. The efficiency of the cell is

  1. A.75%
  2. B.50%
  3. C.33%
  4. D.25%
Show the answer and explanation

Answer: A (75%)

Explanation

Efficiency = useful power/total power = R/(R + r) = 3/(3 + 1) = 75%.