Question

What is the S.I unit of temperature?
(A). Kelvin
(B). Celsius
(C). Fahrenheit
(D). None of the above

Answer 1

- Hint: The S.I. unit is the unit of a quantity that is recognized internationally. There may be more than one unit that defines a quantity but the S.I. unit defines the unit which is listed in the International System of Unit.

Complete step-by-step solution -

The S.I unit of temperature is Kelvin. It is written as ‘K’. The abbreviation S.I. is derived from the French Système international which is the International System of Units.
The S.I. unit is the only unit that is accepted in almost all of the countries of the world. Temperature has three units namely Celsius, Fahrenheit and Kelvin and out of these three the Kelvin scale I internationally recognized and thus it is the S.I. unit.
All the temperature units can be converted into one another. Let us see how.
Kelvin can be converted to Celsius and vice versa using the formula
Kelvin = Celsius + 273.15. For example, for the conversion of 0 K to Celsius,
O = Celsius + 273.15
$\Rightarrow Celsius=0-273.15$
$\Rightarrow Celsius=-273.15$
Therefore, $0K=-273.15^{\circ }C$
Fahrenheit can be converted into Celsius and vice versa using the formula Fahrenheit = $Celsius\times {\displaystyle \frac{9}{5}}+32$
For example, for conversion of ${25}^{\circ }C$ to Fahrenheit,
Fahrenheit = $25\times {\displaystyle \frac{9}{5}}+32$
$\Rightarrow Fahrenheit=5\times 9+32$
$\Rightarrow Fahrenheit=45+32$
$\Rightarrow Fahrenheit={77}^{\circ }F$
Therefore, ${25}^{\circ }C$ is equal to ${77}^{\circ }F$
Kelvin can be converted to Fahrenheit and vice versa using the formula
Fahrenheit = $Kelvin\times {\displaystyle \frac{9}{5}}-459.67$
For example, for the conversion of 350 K to Fahrenheit,
Fahrenheit = $350\times {\displaystyle \frac{9}{5}}-459.67$
$\Rightarrow Fahrenheit=70\times 9-459.67$
$\Rightarrow Fahrenheit=630-459.67$
$\Rightarrow Fahrenheit={170.33}^{\circ }F$
Therefore 350 K is equal to = ${170.33}^{\circ }F$

Note: Fahrenheit and Celsius might be the most widely used temperature unit, but Kelvin is the S.I. unit and it is used in all the calculations of temperatures in physics and chemistry numerical. Don’t get confused.