Unit of Temperature
Temperature is the measure of the hotness or coldness of a body and tells us how much heat energy it has. It is measured using a thermometer and expressed in different units. The SI unit of temperature is Kelvin (K), named after Lord Kelvin. Other commonly used units include Celsius, Fahrenheit, Rankine, and Réaumur. In this topic, students will learn about different temperature scales, their standard reference points like freezing and boiling points of water, and where each scale is commonly used. Understanding temperature units helps students build a strong foundation in thermodynamics, weather studies, and everyday scientific measurements, making it an important concept in physics education.
This Story also Contains
- SI Unit of Temperature
- Other Units of Temperature
- Relation Between Different Units of Temperature
SI Unit of Temperature
- The SI unit of temperature is kelvin.
- The symbol of kelvin is K (not °K).
- It is named after the physicist Lord Kelvin.
- Kelvin is one of the seven fundamental (base) SI units.
Also read -
Other Units of Temperature
Apart from the SI unit kelvin (K), temperature is also measured in several other commonly used units.
These are:
1. Celsius $\left({ }^{\circ} \mathrm{C}\right)$
- Symbol: ${ }^{\circ} \mathrm{C}$
- Also called centigrade scale.
- Water freezes at $\mathbf{0}^{\boldsymbol{\circ}} \mathbf{C}$ and boils at $100^{\boldsymbol{\circ}} \mathbf{C}$.
- It is widely used in daily life and weather reports.
2. Fahrenheit ( ${ }^{\circ} \mathrm{F}$ )
- Symbol: ${ }^{\circ} \mathrm{F}$
- Water freezes at $\mathbf{3 2}^{\boldsymbol{\circ}} \mathbf{F}$ and boils at $\mathbf{2 1 2}^{\boldsymbol{\circ}} \mathbf{F}$.
- Commonly used in countries like the United States.
3. Rankine ( ${ }^{\circ} \mathrm{R}$ or ${ }^{\circ} \mathrm{Ra}$ )
- Symbol: ${ }^{\circ} \mathrm{R}$ (sometimes written as ${ }^{\circ} \mathrm{Ra}$ )
- It is related to the Fahrenheit scale.
- Mainly used in engineering and thermodynamics in some countries.
4. Réaumur ( ${ }^{\circ} \mathrm{Re}$ )
- Symbol: ${ }^{\circ} \mathrm{Re}$
- Water freezes at $0^{\circ} \mathbf{R e}$ and boils at $80^{\circ} \mathbf{R e}$.
- It is rarely used today.
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Related Topics Link, |
Scale Ranges of Temperature Units
The boiling point and freezing point of temperature is best shown with a different unit of temperature in the below table as.
| Scale Factor | Celsius (°C) | Réaumur (°Re) | Fahrenheit (°F) | Kelvin (K) | Rankine (°R) |
| Boiling Point of Water | 100 | 80 | 212 | 373.15 | 671.67 |
| Freezing Point of Water | 0 | 0 | 32 | 273.15 | 491.67 |
Also Read:
Relation Between Different Units of Temperature
1. Celsius and Fahrenheit
$
\begin{aligned}
F & =\frac{9}{5} C+32 \\
C & =\frac{5}{9}(F-32)
\end{aligned}
$
2. Celsius and Kelvin
$
\begin{aligned}
& K=C+273.15 \\
& C=K-273.15
\end{aligned}
$
3. Fahrenheit and Kelvin
$
K=\frac{5}{9}(F-32)+273.15
$
4. Celsius and Réaumur
$
\begin{aligned}
R e & =\frac{4}{5} C \\
C & =\frac{5}{4} R e
\end{aligned}
$
5. Fahrenheit and Rankine
$
\begin{aligned}
& R=F+459.67 \\
& F=R-459.67
\end{aligned}
$
Also check-
- NCERT Exemplar Class 11th Physics Solutions
- NCERT Exemplar Class 12th Physics Solutions
- NCERT Exemplar Solutions for All Subjects
NCERT Physics Notes:
Frequently Asked Questions (FAQs)
The SI unit of temperature is Kelvin. The Kelvin symbol is K. It’s the standard unit of temperature.
The most common unit of temperature is Celsius and its denoted by ℃ . This unit of temperature is widely used in almost every physical measurement of temperature.
The various scales used to measure temperature are listed as
Celsius is the unit of temperature. Its denoted by °C
Fahrenheit is the unit of temperature. Its denoted by ℉
Rankine is a unit of temperature. Its denoted by °Ra
Reaumur is another unit of temperature and Its denoted by °Re
and the SI unit of temperature Kelvin is also used to measure temperature.
The most common three units of temperature are namely Kelvin, Celsius and Fahrenheit. and all these three units of temperature are related as ℉=95℃+32 and °K=℃+273.15
The SI unit of temperature is Kelvin. mole is the SI unit of the amount of substance. The kilogram is the SI unit of mass. Ampere represents electric current. Hence, kelvin is the SI unit of temperature and the kelvin symbol is K. So, the correct option is (D) Kelvin.
