1
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
$${{5} \over 12}$$
2
JEE Main 2018 (Online) 15th April Evening Slot
+4
-1
The value closest to the thermal velocity of a Helium atom at room temperature (300 K) in ms-1 is :
[kB =1.4 $$\times$$ 10-23 J/K; mHe = 7 $$\times$$ 10 -27 kg ]
A
1.3 $$\times$$ 104
B
1.3 $$\times$$ 103
C
1.3 $$\times$$ 105
D
1.3 $$\times$$ 102
3
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
Out of Syllabus
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
$$2520$$ $$J$$
4
JEE Main 2018 (Online) 15th April Morning Slot
+4
-1
One mole of an ideal monoatomic gas is compressed isothermally in a rigid vessel to double its pressure at room temperature, $${27^ \circ }C.$$ The work done on the gas will be :
A
$$300$$ $$R$$
B
$$300$$ $$R$$ $$ln$$ $$6$$
C
$$300$$ $$R$$ $$ln$$ $$2$$
D
$$300$$ $$R$$ $$ln$$ $$7$$
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