2019-03-01_Physics_Times

(a) 0J (b)10J (c) 20J (d) 30J
An ideal monatomic gas expands to twice its vol-
ume. If the process is isothermal, the magnitude of
work done by the gas is Wi. If the process is adia-
batic, the magnitude of work done by the gas is
Wa. Which of the following is true?
(a) W Wi a 0 (b) W Wi a 0
(c) W Wi a 0 (d) W Wa i 0
A container with rigid walls is covered with per-
fectly insulating material.The container is divided
into two parts by a partition. One part contains a
gas while the other is fully evacuated (vacuum).
The partition is suddenly removed. The gas rushes
to fill the entire volume and comes to equilibrium
after a little time. If the gas is not ideal,
(a) The initial internal energy of the gas equals
its final internal energy
(b) The initial temperature of the gas equals its
final temperature
(c) The initial pressure of the gas equals its final
(P) pressure
(d) The initial entropy of the gas equals its final
entropy
Jet aircrafts fly at altitudes above 30,000 ft where
the air is very cold at – 40ºC and the pressure is
0.28 atm. The cabin is maintained at 1 atm pressure
by means of a compressor which exchanges air
from outside adiabatically. In order to have a com-
fortable cabin temperature of 25ºC, we will
require in addition
(a) A heater to warm the air injected into the cabin
(b) An air-conditioner to cool the air injected into
the cabin
(c) Neither a heater nor an air-conditioner ; the
compressor is sufficient
(d) Alternatively heating and cooling in the two
halves of the compressor cycle
One mole of an ideal gas at initial temperature T,
undergoes a quasi-static process during which the
volume V is doubled. During the process the inter-

nal energy U obeys the equation U V ,a^3 where

a is a constant. The work done during this process

is

(a) 3RT / 2 (b) 5RT / 2 (c) 5RT / 3 (d) 7RT / 3

An ideal gas is made to undergo a cycle depicted

by the PV diagram alongside. The curved line from

A to B is an adiabat. Then

(a) The efficiency of this cycle is given by unity

as no heat is released during the cycle

(b) Heat is absorbed in the upper part of the

straight line path and released in the lower part

(c) If T and T 1 2 are the maximum and minimum

temperatures reached during the cycle, then

the efficiency is given by^2

1

1

T

T



(d) The cycle can only be carried out in the

reverse of the direction shown in figure

An ideal gas with heat capacity at constant vol-

ume CV undergoes a quasistatic process described

by PV in a P-V diagram, where  is a constant.

The heat capacity of the gas during this process is

given by

(a) CV (b) C nRV

(c)

V 1

nR

C 



(d)

[2012]

[2011]1]

[2011]1]

[2011]1]

19.

[2010]

20.

[2010]

Heat Transfer

1.

[2017]

V 1 2

nR

C 



Two bottles A and B have radii RAandRBand

heightshAandhB respectively with RB 2 RA and

hB 2 hA.These are filled with hot water at

60 .CConsider that heat loss for the bottles takes

place only from side surfaces.If the time the for the

bottles A and B, respectively, then tAand tBare

best related as

(a) t tAB (b) tB 2 tA (c) tB 4 tA (d) t tAA/ 2