1
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
$${{K({\theta _2} - {\theta _1})({r_2} - {r_1})} \over {4\pi {r_1}{r_2}}}$$
2
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
3
JEE Main 2021 (Online) 31st August Morning Shift
+4
-1
A reversible engine has an efficiency of $${1 \over 4}$$. If the temperature of the sink is reduced by 58$$^\circ$$C, its efficiency becomes double. Calculate the temperature of the sink :
A
174$$^\circ$$C
B
280$$^\circ$$C
C
180.4$$^\circ$$C
D
382$$^\circ$$C
4
JEE Main 2021 (Online) 31st August Morning Shift
+4
-1
For an ideal gas the instantaneous change in pressure 'p' with volume 'v' is given by the equation $${{dp} \over {dv}} = - ap$$. If p = p0 at v =0 is the given boundary condition, then the maximum temperature one mole of gas can attain is : (Here R is the gas constant)
A
$${{{p_0}} \over {aeR}}$$
B
$${{a{p_0}} \over {eR}}$$
C
infinity
D
0$$^\circ$$C
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