Two electronic temperature sensors, T1 T_1\,T1 and T2T_2T2, both initially display the same room temperature. Sensor T1 T_1\,T1 is kept dry and exposed to the air, while the bulb of sensor T2 T_2\,T2 is wrapped in cotton wool soaked in ethanol at room temperature. A fan is then used to blow room-temperature air over both sensors. Which statement correctly describes and explains the resulting temperature readings?
T1T_1T1 reads a lower temperature than T2T_2T2 because the cotton wool insulates sensor T2T_2T2 from the draft.
T1T_1T1 reads a higher temperature than T2T_2T2 because ethanol evaporates from the cotton wool, cooling sensor T2T_2T2 by absorbing thermal energy from it.
Both sensors continue to read the same temperature because the air being blown is at room temperature.
T1T_1T1 reads a lower temperature than T2T_2T2 because the evaporation of ethanol releases heat to sensor T2T_2T2.
528 exam-style questions on CIE IGCSE Physics 2.2 Thermal properties and temperature, covering 2.2.1 Thermal expansion of solids, liquids and gases, 2.2.2a Internal energy and temperature, 2.2.2b Specific heat capacity, 2.2.3a Melting, boiling, condensation and solidification, 2.2.3b Evaporation, and 2.2.3c Cooling by evaporation. Each one has a worked solution and a mark scheme showing where the marks go.