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JAMB Physics 2002 Question 32

Question 32

Current Electricity

An electric cell with nominal voltage E has a resistance of 3Ω connected across it. If the voltage falls to 0.6E, the internal resistance of the cell is

  1. A.4Ω
  2. B.3Ω
  3. C.2Ω
  4. D.1Ω
Show the answer and explanation

Answer: C (2Ω)

Explanation

The 3 Ω resistor gets 0.6E and the internal resistance the remaining 0.4E. With the same current, r = 3 × 0.4/0.6 = 2 Ω.