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JAMB Physics 2013 Question 38

Question 38

Current Electricity

A cell of emf 1.5V is connected in series with a 1Ω resistor and a current of 0.3A flows through the resistor. Find the internal resistance of the cell.

  1. A.4.0Ω.
  2. B.3.0Ω.
  3. C.1.5Ω.
  4. D.1.0Ω.
Show the answer and explanation

Answer: A (4.0Ω.)

Explanation

E = I(R + r): 1.5 = 0.3(1 + r), so 1 + r = 5 and r = 4.0 Ω.