Question

SI unit of temperature is........
(A) K
(B) \[{}^\circ C\]
(C) \[{}^\circ F\]
(D) u

Answer 1

Hint: The SI unit of temperature is not relative to any scale. It shows absolute value.So, at absolute zero temperature, its value is also equal to zero.

Complete step by step answer:
We know that Kelvin, Fahrenheit, and Celsius are units of temperature. The SI units are those units of any quantity that are assigned by SI (Systeme International).
- There are specific units assigned to seven base quantities by SI. It involves temperature also.
- Celsius and Fahrenheit are generally used units of temperatures but none of them is SI units of temperature. So, option (B) and (C) are not correct.
- We can also say that it will be easier to calculate the problems when the absolute value of temperature is put into the formula. It has its own significance. At absolute zero temperature, Kelvin value of temperature is also zero, hence it is absolute value.
- ‘u’ is not a unit of temperature. So, option (D) also gets rejected.
- Let’s see the relation between the units of temperature.
$^{\circ }C=C+273.15K$
\[^{\circ }F=\dfrac{9}{5}C+32\]
\[^{\circ }F=(K-273.15)\times \dfrac{9}{5}+32\]
- Kelvin is the SI unit of temperature and it is denoted by K. It shows absolute value of temperature.
So, the correct answer is “Option A”.

Additional Information:
In earlier times Kelvin was denoted as $^{\circ }K$ but then later on, scientists thought that Kelvin shows absolute value of temperature and hence they should remove the degree sign from the denotion. So, later on they denoted Kelvin as K which has been used since then.

Note: Note that as per new guidelines of SI, there is no degree sign before letter K in the denotation of unit Kelvin. Although we use Celsius more often in our day-to-day life, it is not the SI unit, we need to remember that as it may lead to confusion.