1
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
Out of Syllabus
Two ideal Carnot engines operate in cascade (all heat given up by one engine is used by the other engine to produce work) between temperature, T1 and T2 . The temperature of the hot reservoir of the first engine is T1 and the temperature of the cold reservoir of the second engine is T2 . T is temperature of the sink of first engine which is also the source for the second which is also the source for the second engine. How is T related to T1 and T2 . If both engines perform equal amount of work?
A
$$T = {{2{T_1}{T_2}} \over {{T_1} + {T_2}}}$$
B
$$T = \sqrt {{T_1}{T_2}}$$
C
$$T = {{{T_1} + {T_2}} \over 2}$$
D
T = 0
2
JEE Main 2020 (Online) 7th January Evening Slot
+4
-1
Under an adiabatic process, the volume of an ideal gas gets doubled. Consequently the mean collision time between the gas molecule changes from $${\tau _1}$$ to $${\tau _2}$$ . If $${{{C_p}} \over {{C_v}}} = \gamma$$ for this gas then a good estimate for $${{{\tau _2}} \over {{\tau _1}}}$$ is given by :
A
$${\left( 2 \right)^{{{1 + \gamma } \over 2}}}$$
B
2
C
$${\left( {{1 \over 2}} \right)^{{{1 + \gamma } \over 2}}}$$
D
$${\left( {{1 \over 2}} \right)^\gamma }$$
3
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
Two moles of an ideal gas with $${{{C_P}} \over {{C_V}}} = {5 \over 3}$$ are mixed with 3 moles of another ideal gas with $${{{C_P}} \over {{C_V}}} = {4 \over 3}$$. The value of $${{{C_P}} \over {{C_V}}}$$ for the mixture is :
A
1.50
B
1.45
C
1.47
D
1.42
4
JEE Main 2020 (Online) 7th January Morning Slot
+4
-1
A litre of dry air at STP expands adiabatically to a volume of 3 litres. If $$\gamma$$ = 1.40, the work done by air is : (31.4 = 4.6555) [Take air to be an ideal gas]
A
60.7 J
B
100.8 J
C
90.5 J
D
48 J
EXAM MAP
Medical
NEET