CBSE Class 11-science Answered

The P-V diagram drawn as per the question is shown in the figure.

(i)  Work done during the process from A to B (expansion)

W_AB = + area ABKLA

       = area of triangle ABC + area of rectangle BCLK

       = (1/2 BC x AC) + (KL x LC)

Now, BC = KC = 4 - 1 = 3 litres = 3 x 10^-3 m³

AC = 4 - 2 = 2 Nm^-2  : LC = 2 - 0 = 2 Nm^-2

Therefore, W_AB = 1/2 x 3 x 10^-3 x 2 + 3 x 10^-3 x 2 = 9 x 10^-3 J

(ii)  Work done during the process from B to C (compression) is

W_BC  = - area BCLK = -KL x LC

        = -3 x 10^-3 x 2 = - 6 x 10^-3J.

(iii)  Work done during the process from C to A.  As there is no change in volume of the gas in this process, therefore, W_CA = 0.

Net work done in the complete cycle

W = W_AB + W_BC + W_CA = 9 x 10^-3 + (- 6 x 10^-3) + 0 = 3 x 10^-3 J