WAEC Physics 2025 Objective — Question 13

Question 13 of 51 from the West African Examinations Council (WAEC) Physics 2025 Objective paper, with the correct answer and a full explanation.

A constant voltage source in the circuit below supplies a sinusoidal alternating e.m.f. The voltages marked against the components are the peak values. Determine the peak value of the applied e.m.f.

A. 11.0V
B. 9.0V
C. 8.0V
D. 7.1VCorrect

Explanation

V = √(VR²+(VL-VC)²) = √(3²+(6-2)²) = √(9+16) = √25 = 5V (rms). Peak value V₀ = Vrms×√2 = 5×√2 = 7.1V.

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