1
JEE Main 2021 (Online) 27th July Morning Shift
+4
-1
The number of molecules in one litre of an ideal gas at 300 K and 2 atmospheric pressure with mean kinetic energy 2 $$\times$$ 10$$-$$9 J per molecules is :
A
0.75 $$\times$$ 1011
B
3 $$\times$$ 1011
C
1.5 $$\times$$ 1011
D
6 $$\times$$ 1011
2
JEE Main 2021 (Online) 27th July Morning Shift
+4
-1
In the reported figure, there is a cyclic process ABCDA on a sample of 1 mol of a diatomic gas. The temperature of the gas during the process A $$\to$$ B and C $$\to$$ D are T1 and T2 (T1 > T2) respectively.

Choose the correct option out of the following for work done if processes BC and DA are adiabatic.
A
WAB = WDC
B
C
WBC + WDA > 0
D
WAB < WCD
3
JEE Main 2021 (Online) 27th July Morning Shift
+4
-1
A body takes 4 min. to cool from 61$$^\circ$$ C to 59$$^\circ$$ C. If the temperature of the surroundings is 30$$^\circ$$ C, the time taken by the body to cool from 51$$^\circ$$ C to 49$$^\circ$$ C is :
A
4 min.
B
3 min.
C
8 min.
D
6 min.
4
JEE Main 2021 (Online) 25th July Evening Shift
+4
-1
A heat engine has an efficiency of $${1 \over 6}$$. When the temperature of sink is reduced by 62$$^\circ$$C, its efficiency get doubled. The temperature of the source is :
A
124$$^\circ$$C
B
37$$^\circ$$C
C
62$$^\circ$$C
D
99$$^\circ$$C
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