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.
313 exam-style questions on CIE IGCSE Physics 2.2.3a Melting, boiling, condensation and solidification. Each one has a worked solution and a mark scheme showing where the marks go.