Question

The total work done in the cyclic process

shown in the Fig. 4.19 is -1000 J. (a) What

does the negative sign mean? (b) What is

the change in internal energy and the heat

transferred during this process. (c) What

will happen when the direction of the cycle

is changed?​

Answer 1

$\huge\star\mathfrak\pink{{Answer:-}}$

Solution:

(a) Work done in the process from A to B along path 2 is given by the area under this curve. In this process, volume is increasing therefore the work done is positive.Work done in the process from B to A along path 1 is given by the area under this curve. In this process volume is decreasing therefore the work done is negative.

The total work done during the complete cycle, from A to B along path 2 and form B to A along path 1 is the area enclosed by the closed loop. This is the difference between the area under the curve 1 and that under the curve 2. Since the area under curve 1 is negative and larger than

the area under the curve 2, the area of the loop is also negative. That means the work is done by the system is negative.

(b) This is a cyclic process which means the initial and the final state of the system is the same. For a cyclic process ∆U = 0, so Q = W = - 1000 J. That is, 1000 joules of heat must be rejected by the

system.

(c) If the direction of the cycle is changed the work done will be positive. The system will do work.

For this example we conclude that:

The total work done in a cyclic process is positive if the process is goes around the cycle in a clockwise direction. The total work done in a cyclic process is negative if the process goes

around the cycle in a counterclockwise direction