WAEC Physics 2025 Theory — Question 30
Question 30 of 34 from the West African Examinations Council (WAEC) Physics 2025 Theory paper, with the correct answer and a full explanation.
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1(b)(i) Define the term volt. (ii) A battery has an e.m.f. of 12.0 V and an internal resistance of 0.5 Ω. If a 2 Ω resistor is connected across the battery terminals, calculate the terminal voltage.
Model answer
(i) The volt is the SI unit of electric potential difference; it is (one volt) defined as the potential difference between two points in an electric circuit when one Joule of work is done to move one coulomb of charge from one point to the other. (ii) I = E/(R+r) = 12/(2+0.5) = 12/2.5 = 4.8 A. Terminal voltage, V = IR = 4.8×2 = 9.6 V.
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