Thermometer and Its Types

A thermometer is a device used to measure temperature. It consists of a narrow glass tube with a bulb at one end. The bulb and part of the tube are filled with a liquid, such as alcohol (replacing mercury because mercury is harmful)

• The bulb of the thermometer is placed in contact with the object whose temperature is to be measured.
• The liquid in the bulb expands with the rise in temperature and moves up the glass tube.
• The level of the liquid corresponds to the temperature markings on the thermometer.

When a hot object is placed in contact with a cold object, heat flows from the hot object to the cold one.

1. Laboratory Thermometer (Figure a): Measures a wide range of temperatures, typically from -40°C to 110°C or more. It is used in experiments to measure temperatures of various substances.
2. Clinical Thermometer (Figure b): Designed to measure body temperature, with a limited range of 35°C to 42°C. Commonly used to check if someone has a fever. Features a kink to prevent the liquid from falling back when removed from the body.
3. Digital Thermometer (Figure c): Does not use liquid expansion. It works with a sensor that directly detects the heat emitted from the body to calculate temperature. Commonly used for clinical purposes today.
4. Maximum-Minimum Thermometer (Figure d): Measures the highest and lowest temperatures of the day. It is useful in weather monitoring and environmental studies.

Different thermometers