Clinical Thermometer Design Enhances Sensitivity

Steps:

• Identify purpose: measures narrow body temperature range (35–42°C) unlike lab thermometers' wide range (-10–110°C).
• Compare sensitivity: clinical version uses larger bulb and narrower capillary for greater mercury expansion per degree.
• Evaluate scale: both types have linear scales from uniform expansion.
• Assess constriction: it retains mercury for reading but does not alter sensitivity, which depends on bulb-capillary ratio.

Why B is correct:

• Sensitivity increases with larger bulb volume relative to capillary bore, allowing smaller temperature changes (e.g., 0.1°C) to produce visible mercury rise, per Charles's law on gas/liquid expansion.

Why the others are wrong:

• A: Clinical range is narrower (7°C) than lab thermometers (up to 120°C span).
• C: Linearity is true for all mercury thermometers, not unique to clinical ones.
• D: Constriction prevents mercury fallback for accurate reading but does not affect expansion-based sensitivity.

Final answer: B