WAEC Physics 2023 Paper

Concept:For a cell, the total circuit resistance includes both the external load and the internal resistance.Use the relation $E = I(R + r)$, where $E$ is emf, $I$ is current, $R$ is external resistance, and $r$ is internal resistance.Explanation:Given: $E = 2\ \text{V}$, $r = 0.5\ \Omega$, and $I = 0.4\ \text{A}$.The circuit equation is $E = I(R + r)$.Rearrange to find external resistance: $R = \frac{E}{I} - r$.Substitute the given values: $R = \frac{2}{0.4} - 0.5$.This gives $R = 5 - 0.5$.Therefore, $R = 4.5\ \Omega$.Here, the external resistor is $P$, so $P = 4.5\ \Omega$.Answer:$P = 4.5\ \Omega$Correct option: A. $4.5\ \Omega$