Mechanical thermometers are based on what principle?

Mechanical thermometers are based on what principle?

• A. They are based on the expansion of liquids in a glass column.
• B. They rely on electronic circuits to read temperature.
• C. They rely on infrared radiation to read temperature.
• D. They measure humidity changes to infer temperature.

Answer: (A)

Mechanical thermometers rely on the fact that liquids expand when heated. In a classic design, a small amount of liquid such as mercury or alcohol is sealed in a thin glass tube. As temperature rises, the liquid expands, pushing more into the narrow capillary and causing the level to rise along a calibrated scale. This physical movement directly converts temperature into a readable measurement. Other methods—electronic circuits, infrared radiation sensing, or using humidity changes—involve different physical principles and are not what defines a mechanical thermometer.

Mechanical thermometers rely on the fact that liquids expand when heated. In a classic design, a small amount of liquid such as mercury or alcohol is sealed in a thin glass tube. As temperature rises, the liquid expands, pushing more into the narrow capillary and causing the level to rise along a calibrated scale. This physical movement directly converts temperature into a readable measurement. Other methods—electronic circuits, infrared radiation sensing, or using humidity changes—involve different physical principles and are not what defines a mechanical thermometer.