Thermometer sensitivity increases with narrower bore diameter

Steps:

• Sensitivity is the height change of the liquid column per degree temperature rise.
• Liquid expands by a fixed volume with temperature increase.
• This volume fills the capillary tube, where height h = volume / (π r²).
• Smaller radius r (narrower diameter) yields larger h, boosting sensitivity.

Why B is correct:

• Smaller diameter of the glass tube (bore) reduces cross-sectional area, so the same liquid expansion causes a greater column rise, as per the capillary rise formula h = V / (π r²).

Why the others are wrong:

• A: "Factor of the bore" is imprecise and does not specify the diameter, which is the actual determinant.
• C: Length of the tube sets the measurement range, not the sensitivity per degree.
• D: Thickness provides structural durability but does not influence liquid expansion or column height.

Final answer: B