4.37 - An Introduction to Thermal Physics

Question

A common (but imprecise) way of stating the third law of thermodynamics is "You can't reach absolute zero." Discuss how the third law, as stated in Section 3.2, puts limits on how low a temperature can be attained by various refrigeration techniques.

Step-by-Step Solution

Answer

The refrigeration techniques cannot attain absolute zero temperature

Step 1: Given Information

Given techniques: refrigeration techniques 

How low a temperature can be attained by various refrigeration techniques

Step 2: Explanation

As per the Third law of thermodynamics,  entropy of the system tends to zero at  absolute zero temperature.

As entropy approaches zero at absolute zero temperature therefore the heat capacity also goes to zero. This means that the heat capacity becomes negligibly low at very low temperature.

So the cooling process becomes ineffective for very low heat capacity. This is the reason why refrigeration requires temperature higher than absolute zero.

So we can say that the refrigeration techniques cannot attain absolute zero temperature.