IISER Physics - Heat and Thermodynamics
Exam Duration: 45 Mins Total Questions : 30
What does increase with temperature?
A. Time period of a pendulum
B. Coefficient of Viscosity
C. Wavelength of sound
D. Viscosity
Mark :
- (a)
if A, B are correct
- (b)
if A, C are correct
- (c)
if B, D are correct
- (d)
if C, D are correct
Five moles of perfect diatomic gas are mixed with three moles of a perfact monatomic gas. The ratio of the two specific heats \(Cp/C\vartheta \) for the mixture is
- (a)
1.54
- (b)
1.40
- (c)
1.61
- (d)
1.47
The total heat energy Q is supplied ton mole sof a gas, as a result of which the gas does an a,ount of work W. The temperature of gas will rise be [ \({ C }_{ \vartheta }\) = specific heat at constant volume ]
- (a)
\(\frac { Q }{ n{ C }_{ \vartheta } } \)
- (b)
\(\left( Q-W \right) { C }_{ \vartheta }\)
- (c)
\(\frac { \left( Q-W \right) }{ { C }_{ \vartheta } } \)
- (d)
\(\frac { \left( Q-W \right) }{ { nC }_{ \vartheta } } \)
Estimate the minimum amount of work done that must be done to extract 100 cal of heat from a masssive object at 0\(?\) while rejecting heat to a hot reservoir at a temperature of 20\(?\). This work done is about
- (a)
30 J
- (b)
10 J
- (c)
50 J
- (d)
70 J
Standardisation of the thermometers is obtained with
- (a)
Jolly's thermometer
- (b)
Platinum resistance thermometer
- (c)
Thermocouple thermometer
- (d)
gas thermometer
The ratio \({ C }_{ p }/{ C }_{ \vartheta }=\gamma \) for any perfect gas
- (a)
Cannot be greater than 5/4
- (b)
Cannot be greater than 3/2
- (c)
Cannot be greater than 5/3
- (d)
can have any value
In adiabatic expansion of a gas
- (a)
its pressure increases
- (b)
its temperature falls
- (c)
its density increases
- (d)
its thermal energy increases
A Carnor engine, whose efficieny is 40% takes in heat from a source maintained at a temperature of 500K. It is desired to have an engine of efficiency 60%. Then the intake temperature for the same exhaust(sink) temperature must be
- (a)
efiiency of Carnot engine cannot be made larger than 50%
- (b)
1200K
- (c)
750K
- (d)
600K
A gas has:
- (a)
one specific heat only
- (b)
two specific heats only
- (c)
infinite number of specific heats
- (d)
no specific heat
When heat is added to a system, which of the following is not possible?
- (a)
Internal energy of the system increases
- (b)
Work is done by the system
- (c)
Neither internal energy increases nor work is done by the system
- (d)
Internal energy increases and also work is done by the system
The efficiency of a Carnot heat engine:
- (a)
is independent of the temperature of the source and the sink
- (b)
is independent of the working substance
- (c)
can be 100%
- (d)
is not affected by the thermal capacity of the source or the sink
For a gas, if \(\gamma\) = 1.4, then atomicity, Cp and Cv of the gas are respectively:
- (a)
monoatomic, \(\frac{5R}{2}, \frac{3R}{2}\)
- (b)
monoatomic,\(\frac{7R}{2}, \frac{5R}{2}\)
- (c)
diatomic,\(\frac{7R}{2}, \frac{5R}{2}\)
- (d)
diatomic,\(\frac{7R}{2}, \frac{5R}{2}\)
A gas is compressed at a constant pressure of 50 N/m2 from a volume of 10m3 to a volume of 4 m3. Energy of 100 J is then added to the gas by heating. Its internal energy is:
- (a)
increased by 400 J
- (b)
increased by 200 J
- (c)
increased by 100 J
- (d)
decreased by 200 J
Maximum density of H2O is at the temperature
- (a)
32°F
- (b)
39.2°F
- (c)
42°F
- (d)
4°F
In a resistance thermometer the resistances at O°C and 100°C are 6.74 and 7.74 ohm respectively. The temperature corresponding to 6.53 ohm resistance is:
- (a)
53°C
- (b)
21°C
- (c)
-53°C
- (d)
-21 °C
Two thermometers X and Y have ice points marked at 15° and 25° and steam points marked as 75° and 125° respectively. When thermometer X measures the temperature of a bath as 60° on it, what would thermometer Y read when it is used to measure the temperature of the same bath?
- (a)
60°
- (b)
75°
- (c)
100°
- (d)
90°
Which of the following statements is wrong?
- (a)
Bimetal is used in metal thermometers
- (b)
Bimetal is used in thermostats for regulating the cooling or heating of rooms
- (c)
Bimetal relays are used to open or close electric circuits
- (d)
Bimetals are used to generate electricity
The volume expansion coefficient is:
- (a)
equal to temperature
- (b)
proportional to square root of temperature
- (c)
inversely proportional to square root of temperature
- (d)
inversely proportional to temperature
Two marks on a glass rod 10 em apart are found to increase their distance by 0.08 mm when the rod is heated from O°C to 100° C. A flask made of the same glass as that of rod measures a volume of 1000 cc at O°C. The volume it measures at 100° C (In cc) is:
- (a)
1002.4
- (b)
1004.2
- (c)
1006.4
- (d)
1008.2
A gas under constant pressure of 4.5 x 105 Pa when subjected to 800 kJ of heat, changes the volume from 0.5 m3 to 2.o m3 The change in internal energy of the gas is:
- (a)
6.75x10sJ
- (b)
5.25x10sJ
- (c)
3.25x10sJ
- (d)
1.25x10sJ
A Carnot engine takes heat from a reservoir at 627°C and rejects heat to the sink at 27°C. Its efficiency will be:
- (a)
3/5
- (b)
1/3
- (c)
2/3
- (d)
200/209
At 27°C, a gas is suddenly compressed such that its pressure becomes 1/8th of original pressure. Temperature of the gas will be: (\(\gamma\)=5/3)
- (a)
420 K
- (b)
327°C
- (c)
300 K
- (d)
-142°C
An ideal refrigerator has its freezer at a temperature of -13 oC. The 11of the engine is 17%. The temperature of air is
- (a)
39°C
- (b)
312°C
- (c)
39 K
- (d)
234°C
- (a)
- (b)
- (c)
- (d)
A Carnot's engine operates with source at 127°C and sink at 27°C. If the source supplies 40 kJ of heat energy, the work done by the engine is:
- (a)
30kJ
- (b)
10kJ
- (c)
4 kJ
- (d)
1 kJ
A bubble of 8 mole of helium is submerged at a certain depth in water. The temperature of water increases by 30°C. How much heat is added approximately to helium during expansion?
- (a)
4000 J
- (b)
3000 J
- (c)
3500 J
- (d)
4500 J
- (e)
5000 J
Which One of the figures gives the temperature dependance of density of water correctly?
- (a)
- (b)
- (c)
- (d)
In anomalous expansion of water, at what temperature, the density of water is maximum?
- (a)
>40C
- (b)
40C
- (c)
100C
- (d)
<40C
During an adiabatic compression of 5 moles of a gas, 250 J of work was done. The change in the internal energy will be:
- (a)
50J
- (b)
-150J
- (c)
250J
- (d)
-250J
A solid body of constant heat capacity 1 J/oC is being heated by keeping it in contact with reservoirs in two ways:
(i) Sequentially keeping in contact with 2 reservoirs such that each reservoir supplies same amount of heat.
(ii) Sequentially keeping in contact with 8 reservoirs such that each reservoir supplies same amount of heat. In both the cases body is brought from initial temperature 100 K to final temperature 200 K. Entropy change of the body in the two cases respectively is :
- (a)
In2, 2 In2
- (b)
2In2, 8 In2
- (c)
In2, 4 In2
- (d)
In2, In2