Multiple Choice QuestionsEnergy is being emitted from the surface of a black body at 127°C the rate of 1.0 x 106 J/sm2. The temperature of the black body at which the rate of energy emission is 16.0 x 10° J/sm2 will be
7540C
5270C
2540C
5080C
A body of specific heat 0.2 kcal/ kg° C is heated through 100°C. The percentage increase in its mass is
9%
9.3×10-11 %
10%
None of these
A raft of wood of mass 120 kg floats in water. The weight that can be put on the raft to make it just sink, should be (d raft = 600 kg/m3)
80 kg
50 kg
60 kg
30 kg
A monoatomic gas supplied the heat Q very slowly keeping the pressure constant. The work done by the gas will be
A perfect gas is found to obey the relation PV3/2 = constant during an adiabatic process. If such a gas initially at a temperature T, is compressed to half of its initial volume, then its final temperature will be :
2 T
4T
(2)1/2 T
2 (2)1/2 T
In isothermal process, which of the following is not true?
Temperature remains constant
Internal energy does not change
No heat enters or leaves the system
none of the above
Which of the following processes is reversible?
Transfer of heat by radiation
Electrical heating of a nichrome wire
Transfer of heat by conduction
Isothermal compression
A.
Transfer of heat by radiation
When two bodies are at different temperatures and seperated by distance, the heat transfer between them is called as radiation heat transfer. A reversible process in which system and surroundings can be restored to the initial state from the final state without producing any changes in the thermodynamic properties called revrsible process.
(a) It is the process by which heat is transmitted from one place to another without heating the intervening medium. Hence it is not reversible process.
b) Nichrome wire is made of alloys and has high resistance. When current is passed through it, heat is produced. So, here electrical energy is converted into heat energy. Hence, it is not a
reversible process.
(c) It is the process by which heat is transmitted from one point to another through a substance in the direction of fall of temperature without the actual movement of the particles of the substances themselves. Hence, it cannot be reversible.
d) Isothermal compression is reversible, for example-Carnot cycle, Heat engine. Thus, choice (d) is correct.
An ideal gas heat engine operates in Carnot cycle between 227o C and 127o C. It absorbs 6 × 104 cal of heat at higher temperature. Amount of heat converted to work is
2.4 × 104 cal
6 × 104 cal
1.2 × 104
4.8 × 104 cal
Which of the following parameters does not characterise the thermodynamic state of matter?
Temperature
Pressure
Work
Volume
The work of 146 kJ is performed in order to compress one kilo mole of a gas adiabatically and in this process the temperature of the gas increases by 7°C. The gas is (R= 8.3J mol-1 K-1 )
diatomic
triatomic
a mixture of monoatomic and diatomic
monoatomic
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