Chapter 3, Problem 3A.5P

(a)

Interpretation Introduction

Interpretation:

The reason for the fact that it is impossible to transfer heat from a cold source to the hot sink without some work done has to be stated.

Concept introduction:

The term entropy is used to represent the randomness in a system.  When a system moves from an ordered arrangement to a less order arrangement, then the entropy of the system increases.  The second law of thermodynamics state that the entropy of the system either increases or remain the same.

(b)

Interpretation Introduction

Interpretation:

The magnitude of work need to transfer heat of magnitude $\left|q\right|+\left|w\right|$ from cold source to hot sink has to be predicted.

Concept introduction:

The efficiency of a machine is defined as the ratio of fruitful output and total input.  The efficiency of a machine is used to determine the effectiveness of the machine.  When the efficiency of the machine is high, the machine is very efficient.  The efficiency of a machine cannot be $100\%$.