Physics
Physics
Problem
A clinical thermometer placed under a patient’s tongue stabilises at . Which one of the following is the correct inference from this observation? a) Since the thermometer reads , the patient is hotter than the room. b) The patient and the thermometer have reached thermal equilibrium and hence share the same temperature. c) The thermometer reading stops rising because the heat capacities of the patient and the thermometer are momentarily equal. d) The thermometer has absorbed exactly the same amount of heat that the patient’s body has lost.Intuitive explanation
The core concept here is thermal equilibrium — when two objects reach the same temperature, heat flow between them stops. The key insight is that a thermometer's reading tells you the temperature of whatever it's in contact with, not necessarily the thermometer itself. Since the thermometer stabilizes at 38°C, it has reached thermal equilibrium with the patient's mouth, meaning the patient's body temperature at that location is 38°C. This is a direct measurement of the patient's actual temperature, not a property of the thermometer alone.
Intuitive explanation
The core concept here is thermal equilibrium — when two objects reach the same temperature, heat flow between them stops. The key insight is that a thermometer's reading tells you the temperature of whatever it's in contact with, not necessarily the thermometer itself. Since the thermometer stabilizes at 38°C, it has reached thermal equilibrium with the patient's mouth, meaning the patient's body temperature at that location is 38°C. This is a direct measurement of the patient's actual temperature, not a property of the thermometer alone.