A perfectly
insulated container of volume V is divided into equal halves by a partition.
One side is under vacuum while the other side has one mole of an ideal gas
(with constant heat capacity) at 298 K. If the partition is broken, the final
temperature of the gas in the container
(A)
Will be greater than 298 K
(B)
Will be 298 K
(C)
Will be less than 298 K
(D)
Cannot be determined
GATE
2004
Answer: (B)
A car tyre of
volume 0.057 m3 is inflated to 300 KPa at 300 K. After the car is
driven for ten hours, the pressure in the tyre increases to 330 KPa. Assume air
is an ideal gas and CV for air is 21 J/(mol.K). The change in the internal
energy of air in the tyre in J/mol is
(A)
380
(B)
630
(C)
760
(D)
880
GATE
2004
Answer: (B)
A gas obeys P(V-b)
= RT. The work obtained from reversible isothermal expansion of one mole of
this gas from an initial molar volume Vi to final molar volume Vf
is
GATE 2004
Answer: (D)
Which
of the following statement is TRUE
(A)
Heat can be fully converted into work
(B)
Work cannot fully converted into heat
(C)
The efficiency of heat engine increases
as the temperature of the heat source is increased while keeping the
temperature of the heat sink fixed.
(D)
A cyclic process can be devised whole
sole effect is to transfer heat from a lower temperature to a higher
temperature
GATE
2005
Answer: (C)
A carnot heat
engine cycle is working with an ideal gas. The work performed by the gas during
the adiabatic expansion and compression steps, W1 and W2
respectively are related as
(A)
W1 > W2
(B)
W1 < W2
(C)
W1 = W2
(D)
W1 = - W2
GATE
2005
Answer: (D)
What is the actual power required to drive a
reciprocating air compressor which has to compress 34 m3 of air per
minute from 1.013×105 N/m2 to 4.052×105 N/m2?
Assume that PV1.25 is constant where P is the pressure and v is the
volume, and the efficiency of the compressor is 85%.
(A)
107.9
KW
(B)
200 KW
(C)
82.6 KW
(D)
91.7 KW
GATE
2005
Answer: (A)
A
heat engine operates at 75% of the maximum possible efficiency. The ratio of
the heat source temperature (in K) to the heat sink temperature (in K) is 5/3.
The fraction of the heat supplied that is converted to work is
(A) 0.2
(B) 0.3
(C) 0.4
(D) 0.6
GATE
2006
Answer: (B)
For
the isentropic expansion of an ideal gas from the initial conditions P1,
T1 to the final conditions P2, T2, which ONE
of the following relations is valid ? ( γ = Cp /Cv)
GATE 2006
Answer: (B)
The
change in entropy of the system, undergoing a cyclic irreversible process is
(A)
Greater than 0
(B)
Equal to zero
(C)
Less than zero
(D)
Equal to the Δsurroundings
GATE
2007
Answer: (B)
Which of the
following represents the Carnot cycle (ideal engine)?
GATE
2007
Answer: (C)
2 kg of steam in
a piston –cylinder device at 400 kPa and 175⁰C
under goes a mechanically reversible, isothermal compression to a final
pressure such that the steam becomes just saturated. What is the work, W,
required for the process. Data:
T
= 175⁰C, p = 400 kPa, v = 0.503 m3/kg,
u = 2606 kJ/kg, s = 7.055 kJ/kg-K, T = 175⁰C,
satd. Vapour – v =0.216 m3/kg, u = 2579 kJ/kg, s = 6.622 kJ/kg-K
(A)
0 kJ
(B)
230 kJ
(C)
334 kJ
(D)
388 kJ
GATE
2007
Answer: (C)
A
perfectly insulated cylinder of volume 0.6 m3 is initially divided
into two parts by a thin, frictionless piston, as shown in the figure. The
smaller part of volume 0.2 m3 has ideal gas at 6 bar pressure and
100⁰C. The other part is evacuated.
At certain instant of time t, the stopper is removed and the piston moves out freely to the other end. The final temperature is
(A)
-149⁰C
(B)
-33⁰C
(C)
33⁰C
(D)
100⁰C
GATE
2007
Answer: (D)
For
a Carnot refrigerator operating between 40⁰C
and 25⁰C, the coefficient of performance is
(A)
1
(B)
1.67
(C)
19.88
(D)
39.74
GATE 2008
Answer: (C)
The
work done by one mole of a van der Waals fluid undergoing reversible isothermal
expansion from initial volume Vi to final volume Vf is
Answer: (D)
Common data for the next two questions
An ideal gas with molar heat capacity CP
= 5/2R (where R = 8.314 J/mol.K) is compressed adiabatically from 1 bar and 300
K to pressure P2 in a closed system. The final temperature after
compression is 600 K and the mechanical efficiency of compression is 50%.
The
work required for compression (in kJ/mol) is
(A)
3.74
(B)
6.24
(C)
7.48
(D)
12.48
GATE
2009
Answer: (C)
The
final pressure P2 (in bar) is
(A)
23/4
(B)
25/4
(C)
23/2
(D)
25/2
GATE 2009
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