JAMB Physics 2019 Paper

Concept:Thermocouple e.m.f. is directly proportional to the temperature difference between its junctions.Explanation:The millivoltmeter gives $4\text{ mV}$ when one junction is at $0^\circ\text{C}$ and the other is at $100^\circ\text{C}$.Therefore, $4\text{ mV}$ corresponds to a temperature difference of $100^\circ\text{C}$.The maximum readable voltage is $E_\theta = 10\text{ mV}$.Using proportion:$$\frac{E_\theta}{E_{100}} = \frac{\theta}{100^\circ\text{C}}$$Substitute the values:$$\frac{10\text{ mV}}{4\text{ mV}} = \frac{\theta}{100^\circ\text{C}}$$$$\theta = \frac{10}{4} \times 100^\circ\text{C} = 250^\circ\text{C}$$So the maximum temperature this arrangement can measure is $250^\circ\text{C}$.Answer:C. $250^\circ\text{C}$