JAMB Physics 2020 Paper

Concept:A liquid-in-glass thermometer measures temperature by relating the length of the liquid column to the linear scale between fixed points.Explanation:On the Celsius scale, the lower fixed point is $0^{\circ}\mathrm{C}$ and the upper fixed point is $100^{\circ}\mathrm{C}$.The total distance between these fixed points on the thermometer is $210\,\mathrm{mm}$.The mercury column rises $49\,\mathrm{mm}$ above the lower fixed point.Temperature is proportional to the length of the mercury column, so compare the measured rise to the total scale length.Let the room temperature be $\theta$.Using the relation:$$\frac{\text{length above lower fixed point}}{\text{distance between fixed points}} = \frac{\theta - 0}{100 - 0}$$$$\frac{49}{210} = \frac{\theta}{100}$$Cross-multiply:$$49 \times 100 = 210 \times \theta$$$$\theta = \frac{4900}{210} = 23.33^{\circ}\mathrm{C}$$Therefore, the room temperature is approximately $23.3^{\circ}\mathrm{C}$.Answer:Option B: $23.3^{\circ}\mathrm{C}$