Chapter at a Glance: Temperature & its Measurement | Physics for JAMB PDF Download

Concept of Temperature

• Temperature is a measure of the average kinetic energy of the particles in a substance.
• It determines the hotness or coldness of an object or the surroundings.
• The SI unit of temperature is Kelvin (K).

Thermometric Properties

• Thermometric properties are the properties of substances that change with temperature and are used for measuring temperature.
• Some common thermometric properties include expansion of solids, liquids, and gases, change in electrical resistance, change in pressure, etc.

Calibration of Thermometers

• Calibration is the process of determining the relationship between the thermometric property and temperature.
• It involves comparing the readings of a thermometer with the readings of a standard thermometer.
• Calibration ensures accuracy and reliability of temperature measurements.

Temperature Scales - Celsius and Kelvin

• Celsius Scale: The Celsius scale is based on the properties of water. The freezing point of water is defined as 0°C, and the boiling point of water is defined as 100°C at standard atmospheric pressure.
• Kelvin Scale: The Kelvin scale is an absolute temperature scale. The lowest possible temperature, called absolute zero, is defined as 0 K. The Kelvin scale does not use the degree symbol.

Types of Thermometers

• Liquid-in-Glass Thermometer: It uses the expansion of a liquid, such as mercury or alcohol, to measure temperature.
• Thermocouple: It utilizes the Seebeck effect, where a voltage is generated when two different metals are joined at different temperatures.
• Resistance Thermometer (RTD): It measures temperature based on the change in electrical resistance of a metal wire with temperature.
• Infrared Thermometer: It measures temperature by detecting and converting the emitted infrared radiation from an object.

Conversion from One Scale of Temperature to Another:

Celsius to Kelvin: K = °C + 273.15
Kelvin to Celsius: °C = K - 273.15
Example: Convert 25°C to Kelvin:
K = 25 + 273.15
K = 298.15 K

Note: The conversion between Celsius and Kelvin involves adding or subtracting a constant value of 273.15.