WAEC Physics 2022 Paper

Concept:When identical cells are connected in parallel, the total emf equals the emf of one cell, while their internal resistances combine like resistors in parallel.Explanation:For three cells of internal resistance $2\ \Omega$ connected in parallel, the equivalent internal resistance is$\frac{1}{r_T}=\frac{1}{2}+\frac{1}{2}+\frac{1}{2}=\frac{3}{2}$.So, $r_T = \frac{2}{3}\ \Omega \approx 0.67\ \Omega$.The total emf of the parallel combination remains $E = 1.0\ \text{V}$.The total resistance in the circuit is$R_{\text{total}} = R + r_T = 3 + \frac{2}{3} = \frac{11}{3}\ \Omega$.Using Ohm's law, the current is$I = \frac{E}{R_{\text{total}}} = \frac{1}{\frac{11}{3}} = \frac{3}{11} \approx 0.27\ \text{A}$.Rounding to two decimal places, $0.27\ \text{A} \approx 0.30\ \text{A}$.Answer:The current in the resistor is approximately $0.30\ \text{A}$, which matches option C.