Lesson 1 Objective

At the end of this section, you should be able to:

• define thermometer;
• describe different temperature scales;
• design temperature scales using local materials.
• list different types of thermometers;
• describe the uses of different thermometers.

Brainstorming Question

Which temperature scales do you come across in your life? Which scale do physicians use to measure your body temperature? What are the thermometric properties of mercury thermometer, alcohol thermometer, thermocouple, resistance thermometer and radiation thermometer?

key terms and concepts

• Thermometers are crucial for precise temperature measurement, relying on the physical properties of materials.
• The three main temperature scales are Celsius, Fahrenheit, and Kelvin, each suited for different contexts.
• Various types of thermometers exist, each with specific applications, ranging from household uses to industrial and scientific purposes.

Measuring Temperature with Different Thermometric Scales

• Thermometers: Thermometers are essential instruments for accurately measuring the temperature of a body or substance.
• Temperature Scales:
  • Celsius (°C): Developed by Anders Celsius, this scale is widely used worldwide. It defines the freezing point of water at 0°C and the boiling point at 100°C.
  • Fahrenheit (°F): Created by Daniel Fahrenheit, this scale is commonly used in the United States. Water freezes at 32°F and boils at 212°F, with 180 divisions between these points.
  • Kelvin (K): Developed by Lord Kelvin, this scale is primarily used in scientific contexts. It starts at absolute zero, the lowest possible temperature (-273.15°C), where molecular motion stops. The Kelvin scale does not use degrees, just K.

Types of Thermometers and Their use

1. Mercury Thermometer: Measures temperature through mercury expansion, used in household and industrial settings, from -30°C to 300°C.
2. Alcohol Thermometer: Uses alcohol, safer than mercury, for measuring lower temperatures between -115°C and 78°C.
3. Resistance Thermometer: Measures temperature by the change in electrical resistance of materials like platinum, accurate from -270°C to +700°C.
4. Thermocouple: Generates a voltage from two metals to measure temperatures ranging from -270°C to 2300°C, commonly used in labs and industry.
5. Thermistor: A resistor with temperature-dependent resistance, ideal for precise measurements within a limited range in medical and electronic devices.
6. Radiation Thermometer: Measures temperature via infrared radiation, allowing non-contact measurement, often used in industrial settings.