1
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
2
JEE Main 2018 (Offline)
+4
-1
The mass of a hydrogen molecule is 3.32 $$\times$$ 10-27 kg. If 1023 hydrogen molecules strike, per second, a fixed wall of area 2 cm2 at an angle of 45o to the normal, and rebound elastically with a speed of 103 m/s, then the pressure on the wall is nearly:
A
2.35 $$\times$$ 103 N m-2
B
4.70 $$\times$$ 103 N m-2
C
2.35 $$\times$$ 102 N m-2
D
4.70 $$\times$$ 102 N m-2
3
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
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
$${{5} \over 12}$$
4
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
A Carnot's engine works as a refrigerator between $$250$$ K and $$300$$ K. It receives $$500$$ cal heat from the reservoir at the lower temperature. The amount of work done in each cycle to operate the refrigerator is :
A
$$420$$ $$J$$
B
$$772$$ $$J$$
C
$$2100$$ $$J$$
D
$$2520$$ $$J$$
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