1
JEE Main 2021 (Online) 25th July Evening Shift
MCQ (Single Correct Answer)
+4
-1
Out of Syllabus
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
2
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
3
JEE Main 2021 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
A monoatomic ideal gas, initially at temperature T1 is enclosed in a cylinder fitted with a frictionless piston. The gas is allowed to expand adiabatically to a temperature T2 by releasing the piston suddenly. If l1 and l2 are the lengths of the gas column, before and after the expansion respectively, then the value of $${{{T_1}} \over {{T_2}}}$$ will be :
A
$${\left( {{{{l_1}} \over {{l_2}}}} \right)^{{2 \over 3}}}$$
B
$${\left( {{{{l_2}} \over {{l_1}}}} \right)^{{2 \over 3}}}$$
C
$${{{l_2}} \over {{l_1}}}$$
D
$${{{l_1}} \over {{l_2}}}$$
4
JEE Main 2021 (Online) 25th July Morning Shift
MCQ (Single Correct Answer)
+4
-1
Two different metal bodies A and B of equal mass are heated at a uniform rate under similar conditions. The variation of temperature of the bodies is graphically represented as shown in the figure. The ratio of specific heat capacities is :

A
$${8 \over 3}$$
B
$${3 \over 8}$$
C
$${3 \over 4}$$
D
$${4 \over 3}$$
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