JAMB Physics 2018 Objective — Question 13

Question 13 of 38 from the Joint Admissions and Matriculation Board (JAMB) Physics 2018 Objective paper, with the correct answer and a full explanation.

A cell supplies current of 0.6A and 0.2A through 1.0Ω and 4.0Ω resistors respectively. What is the internal resistance of the cell?

A. 4Ω
B. 2Ω
C. 1Ω
D. 0.5ΩCorrect

Explanation

Using E=I(R+r) for both cases and solving simultaneously: 0.6(1+r)=0.2(4+r) → 0.6+0.6r=0.8+0.2r → 0.4r=0.2 → r=0.5Ω.

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