TITLE.PM5

COMPETITIVE EXAMINATIONS QUESTIONS 905

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\M-therm\Comp1.pm5

3. The heat transfer Q, the work done W and the change in internal energy ∆U are all zero in
   the case of
   (a) a rigid vessel containing steam at 150°C left in the atmosphere which is at 25°C.
   (b) 1 kg of gas contained in an insulated cylinder expanding as the piston move slowly
   outwards.
   (c) a rigid vessel containing ammonia gas connected through a valve to an evacuated rigid
   vessel, the vessel, the valve and the connecting pipes being well insulated and the valve
   being opened and after a time, conditions through the two vessel becoming uniform.
   (d) 1 kg of air flowing adiabatically from the atmosphere into a previously evacuated bottle.


4. Zeroth Law of thermodynamics states that
   (a) two thermodynamic system are always in thermal equilibrium with each other.
   (b) if two systems are in thermal equilibrium, then the third system will also be in thermal
   equilibrium.
   (c) two systems not in thermal equilibrium with a third system are also not in thermal
   equilibrium with each other.
   (d) when two systems are in thermal equilibrium with a third system, they are in thermal
   equilibrium with each other.


5. Which one of the following statements applicable to a perfect gas will also be true for an
   irreversible process? (Symbols have the usual meanings)
   (a)dQ = du + pdV (b)dQ = Tds
   (c)Tds = du + pdV (d) None of the above.


6. The throttling process undergone by a gas across
   an orifice is shown by its states in Fig. 3.

It can be represented on the T-s diagram as

123

TT

ss

1

23

(a) (b)

1

2

3

T T

s s

1

2

3

(c) (d)

Fig. 4

Fig. 3

123