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910 ENGINEERING THERMODYNAMICS

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23. Four processes of a thermodynamic cycle are shown above in Fig. 11 on the T-s plane in the
    sequence 1—2—3—4. The corresponding correct sequence of these processes in the p-V
    plane as shown in Fig. 12 will be

3

4

1

2

T

s

T

A

D

C

B

V

Fig. 11 Fig. 12

(a) (C—D—A—B)(b) (D—A—B—C)

(c) (A—B—C—D)(d) (B—C—D—A).

24. The Fig. 13 shows an isometric cooling process
    1-2 of a pure substance. The ordinate and
    abscissa are respectively
    (a) pressure and volume
    (b) enthalpy and entropy
    (c) temperature and entropy
    (d) pressure and enthalpy.


25. For a thermodynamic cycle to be irreversible,
    it is necessary that

(a)

δQ

T

z =^0 (b) δQ

T

z <^0

(c) δQ

T

z >^0 (d) δQ

T

z ≥^0.

26. Neglecting changes in kinetic energy and potential energy, for unit mass the availability in
    a non-flow process becomes a = φ – φ 0 where φ is the availability function of the
    (a) open system (b) closed system
    (c) isolated system (d) steady flow process.


27. It can be shown that for a simple compressible substance, the relationship

cc TV

T

p

p v PTv

−= F

HG

I

KJ

F

HG

I

KJ

• ∂
  ∂

∂

∂

2

exists

where cp and cv are specific heats at constant pressure and constant volume respectively, T

is temperature, V is volume and p is pressure.

Which one of the following statements is NOT true?

(a) cp is always greater than cv

(b) The right side of the equation reduces to R for an ideal gas

1

2

Fig. 13