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1
JEE Main 2021 (Online) 27th July Morning Shift
MCQ (Single Correct Answer)
+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.
2
JEE Main 2021 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
+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
3
JEE Main 2021 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Two spherical soap bubbles of radii r1 and r2 in vacuum combine under isothermal conditions. The resulting bubble has a radius equal to :
A
$${{{r_1}{r_2}} \over {{r_1} + {r_2}}}$$
B
$$\sqrt {{r_1}{r_2}} $$
C
$$\sqrt {r_1^2 + r_2^2} $$
D
$${{{r_1} + {r_2}} \over 2}$$
4
JEE Main 2021 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
For a gas CP $$-$$ CV = R in a state P and CP $$-$$ CV = 1.10 R in a state Q, TP and TQ are the temperatures in two different states P and Q respectively. Then
A
TP = TQ
B
TP < TQ
C
TP = 0.9 TQ
D
TP > TQ
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