1
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
Two moles of helium are mixed with n moles of hydrogen. If $${{Cp} \over {Cv}} = {3 \over 2}$$ for the mixture, then the value of n is :
A
1
B
3
C
2
D
3 / 2
2
JEE Main 2018 (Online) 16th April Morning Slot
+4
-1
One mole of an ideal monoatomic gas is taken along the path ABCA as show in the PV diagram. The maximum temperature attained by the gas along the path BC is given by :

A
$${{25} \over {16}}\,{{{P_o}{V_o}} \over R}$$
B
$${{25} \over {8}}\,{{{P_o}{V_o}} \over R}$$
C
$${{25} \over {4}}\,{{{P_o}{V_o}} \over R}$$
D
$${{5} \over {8}}\,{{{P_o}{V_o}} \over R}$$
3
JEE Main 2018 (Offline)
+4
-1
Two moles of an ideal monatomic gas occupies a volume V at 27oC. The gas expands adiabatically to a volume 2 V. Calculate (a) the final temperature of the gas and (b) change in its internal energy.
A
(a) 195 K (b) 2.7 kJ
B
(a) 189 K (b) 2.7 kJ
C
(a) 195 K (b) –2.7 kJ
D
(a) 189 K (b) – 2.7 kJ
4
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
Out of Syllabus
Two Carnot engines A and B are operated in series. Engine A receives heat from a reservoir at 600 K and rejects heat to a reservoir at temperature T. Engine B receives heat rejected by engine A and in turn rejects it to a reservoir at 100 K. If the efficiencies of the two energies A and B are represented by $${\eta _A}$$ and $${\eta _B},$$ respectively, then what is the value of $${{{\eta _B}} \over {{\eta _A}}}$$ ?
A
$${{12} \over 7}$$
B
$${{7} \over 12}$$
C
$${{12} \over 5}$$
D
$${{5} \over 12}$$
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