1
JEE Main 2022 (Online) 24th June Morning Shift
+4
-1
Out of Syllabus

A Carnot engine whose heat sinks at 27$$^\circ$$C, has an efficiency of 25%. By how many degrees should the temperature of the source be changed to increase the efficiency by 100% of the original efficiency?

A
Increases by 18$$^\circ$$C
B
Increases by 200$$^\circ$$C
C
Increases by 120$$^\circ$$C
D
Increases by 73$$^\circ$$C
2
JEE Main 2022 (Online) 24th June Morning Shift
+4
-1

Two metallic blocks M1 and M2 of same area of cross-section are connected to each other (as shown in figure). If the thermal conductivity of M2 is K then the thermal conductivity of M1 will be :

A
10 K
B
8 K
C
12.5 K
D
2 K
3
JEE Main 2021 (Online) 31st August Evening Shift
+4
-1
Two thin metallic spherical shells of radii r1 and r2 (r1 < r2) are placed with their centres coinciding. A material of thermal conductivity K is filled in the space between the shells. The inner shell is maintained at temperature $$\theta$$1 and the outer shell at temperature $$\theta$$2($$\theta$$1 < $$\theta$$2). The rate at which heat flows radially through the material is :-
A
$${{4\pi K{r_1}{r_2}({\theta _2} - {\theta _1})} \over {{r_2} - {r_1}}}$$
B
$${{\pi {r_1}{r_2}({\theta _2} - {\theta _1})} \over {{r_2} - {r_1}}}$$
C
$${{K({\theta _2} - {\theta _1})} \over {{r_2} - {r_1}}}$$
D
$${{K({\theta _2} - {\theta _1})({r_2} - {r_1})} \over {4\pi {r_1}{r_2}}}$$
4
JEE Main 2021 (Online) 31st August Evening Shift
+4
-1
A mixture of hydrogen and oxygen has volume 500 cm3, temperature 300 K, pressure 400 kPa and mass 0.76 g. The ratio of masses of oxygen to hydrogen will be :-
A
3 : 8
B
3 : 16
C
16 : 3
D
8 : 3
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