1. The SI unit of temperature is the kelvin (K). Temperature is also expressed in °C (degree Celsius) and °F (degree Fahrenheit).

\(\cfrac{F-32}{9}\) = \(\cfrac{C}5\); K = C + 273.15

∴ F = \(\cfrac{9}5\) C + 32 = \(\cfrac{9}5\) (K - 273.15) + 32

Here, C denotes temperature in °C, F denotes temperature in 0F and K denotes temperature in K (kelvin).

Notes: 

(i) The unît degree Celsius is named in honour of Anders Celsius (1701 – 44) Swedish astronomer. He devised a temperature scale in 1742. 

(ii) The unit degree Fahrenheit is named in honour of Gabriel Daniel Fahrenheit (1686 – 1736) German physicist. He developed the mercury thermometer and devised the temperature scale.

(iii) The unit kelvin is named in honour of William Thomson, 1st Baron Kelvin (of Largs) (1824 – 1907) British physicist and electrical engineer. He made significant contribution in thermodynamics and electromagnetic theory. He proposed a scale of temperature now known as the Kelvin scale or thermodynamic scale.