Which of the following is the SI unit of temperature?
Kelvin
Understanding the SI Unit of Temperature
The International System of Units (SI) is the standard system of measurement used globally in science and industry. It defines a set of base units for fundamental physical quantities. Temperature is one such fundamental quantity.
What is Temperature?
Temperature is a physical quantity that expresses the degree of hotness or coldness of a substance or environment. It is a measure of the average kinetic energy of the atoms or molecules within a system. Different scales exist for measuring temperature, such as Celsius, Fahrenheit, Réaumur, and Kelvin.
Identifying the SI Unit of Temperature
The question asks for the specific unit of temperature that is part of the SI system. Let's examine the options provided:
- Ampere: The ampere (A) is the SI unit of electric current, not temperature.
- Réaumur scale: The Réaumur scale is a temperature scale where water freezes at 0°Ré and boils at 80°Ré. While it measures temperature, it is not the SI unit.
- Candela: The candela (cd) is the SI unit of luminous intensity, which measures the power emitted by a light source in a particular direction. It is not related to temperature.
- Kelvin: The kelvin (K) is the SI base unit of thermodynamic temperature. The Kelvin scale is an absolute thermodynamic scale where absolute zero (the theoretical point at which fundamental particles of nature have minimal vibrational motion, retaining only quantum mechanical zero-point energy) is 0 K.
Based on the definitions of the fundamental SI units, the unit of temperature in the SI system is the kelvin.
Base SI Units Table
| Quantity | SI Base Unit | Symbol |
|---|---|---|
| Length | metre | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Thermodynamic temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
As seen in the table, the SI base unit for thermodynamic temperature is the kelvin (K).
Conclusion
The SI unit for temperature is the kelvin. The other options represent different physical quantities or non-SI temperature scales.
Revision Table: SI Unit of Temperature
| Concept | Description |
|---|---|
| SI Unit of Temperature | Kelvin (K) |
| Definition of Kelvin | The unit of thermodynamic temperature, defined in terms of the Boltzmann constant. |
| Other Temperature Scales | Celsius (°C), Fahrenheit (°F), Réaumur (°R or °Re) - not SI units. |
| Absolute Zero | 0 K or -273.15 °C |
Additional Information on Temperature and SI Units
The Kelvin scale is particularly important in science because it is an absolute scale. This means that 0 K corresponds to absolute zero, the lowest theoretically possible temperature. Temperature differences in Kelvin are equal to temperature differences in Celsius (e.g., a 10 K change is the same as a 10 °C change), but the zero points are different (0 °C = 273.15 K). The Kelvin scale is used extensively in scientific formulas and calculations involving gases and thermodynamics.
Understanding the SI units is crucial in physics and other sciences as they provide a consistent framework for measurements worldwide. Each base unit is defined based on fundamental physical constants, ensuring accuracy and reproducibility.
Important Questions from Units, Dimensions and Measurements
- Arrange the following bands of electromagnetic spectrum in ascending order of their wave length
A. X - rays
B. Near Infrared rays
C. Microwaves
D. Visible Rays
E. Radio waves
Choose the correct answer from the options given below: The light year is a measure of _____, not ______.
The SI unit of mechanical power is:
The boiling points of diethyl ether, benzene, and dimethyl ether are 34.6 ∘ C, 80.1 ∘ C, and -24 ∘ C respectively. Which one of the following correctly represents their boiling points in the Kelvin scale respectively?
A student measure certain lengths using a meter scale having least count equal to 1 mm. Which of the following measurements are more precise?
