WAEC Physics 2024 Paper

Concept:In a series RLC circuit with sinusoidal alternating current, the applied peak e.m.f. is the phasor sum of the peak voltages across the resistor, inductor, and capacitor.Explanation:The resistor voltage $V_R = 3\text{ V}$ and the reactive voltage $(V_L - V_C)$ are $90^\circ$ out of phase.So, the total applied peak e.m.f. is given by:$$V = \sqrt{V_R^2 + (V_L - V_C)^2}$$Substitute the given values:$$V = \sqrt{3^2 + (6 - 2)^2}$$$$V = \sqrt{9 + 16}$$$$V = \sqrt{25}$$$$V = 5\text{ V}$$Answer:The peak value of the applied e.m.f. is $5\text{ V}$, so the correct option is C. 5V.