Absolute Zero and the Kelvin (Absolute) Temperature Scale

The exact value is -273.15 C = 0 K. In NEET numerical problems you almost always round it to -273 C (so you add 273, not 273.15). Use 273 unless the question gives data precise enough to need 273.15. Both are correct; 273 is the practical exam value.

Temperature measures the average kinetic energy (molecular motion) of the particles. At absolute zero the molecular activity is the least possible, so there is no motion left to remove. You cannot have less than the least, so 0 K is the true floor. This is why the Kelvin scale has no negative values.

They differ only in their starting point (origin), not in step size. One kelvin equals one degree Celsius in size. Celsius starts at the ice point (0 C), while Kelvin starts at absolute zero (0 K = -273.15 C). So the numbers differ by 273.15 but a change of 1 C is the same as a change of 1 K.

No. We write 300 K, not 300 degree K. Kelvin is an absolute unit, so the degree symbol is dropped. Celsius keeps the symbol: 27 C is written as 27 degree C.

Gas laws, the ideal gas equation PV = nRT, Stefan-Boltzmann law (E proportional to T to the power 4), and Carnot efficiency all use absolute temperature. These formulas only work when T is in Kelvin, because ratios like T2/T1 become meaningless if you use Celsius (you could divide by zero or get negatives).

The kelvin (K). It is one of the seven SI base units and is the absolute measure of thermodynamic temperature.

Absolute zero is 0 K = -273.15 C = -459.67 F. In NEET you usually use -273 C.

T (in K) = tC + 273.15, or simply T = tC + 273 for exam use. To go back, tC = T - 273.

Yes. Because both scales have the same degree size, a temperature difference of 10 C is exactly a difference of 10 K. Only the reference zero is different.

It is the temperature at which every substance has the least possible molecular activity, that is, minimum internal kinetic energy. No lower temperature is possible.