1
JEE Main 2019 (Online) 10th January Morning Slot
+4
-1
A heat source at T = 103 K is connected to another heat reservoir at T = 102 K by a copper slab which is 1 mthick. Given that the thermal conductivity of copper is 0.1 WK–1m–1, the energy flux through it in the steady state is -
A
200 Wm$$-$$2
B
65 Wm$$-$$2
C
120 Wm$$-$$2
D
90 Wm$$-$$2
2
JEE Main 2019 (Online) 10th January Morning Slot
+4
-1
Out of Syllabus
Three Carnot engines operate in series between a heat source at a temperature T1 and a heat sink at temperature T4 (see figure). There are two other reservoirs at temperature T2 and T3, as shown, with T1 > T2 > T3 > T4. The three engines are equally efficient if -

A
T2 = (T13T4)1/4;  T3 = (T1T43)1/4
B
T2 = (T1T4)1/2;  T3 = (T12T4)1/3
C
T2 = (T1T42)1/3;  T3 = (T12T4)1/3
D
T2 = (T12T4)1/3;  T3 = (T1T42)1/3
3
JEE Main 2019 (Online) 9th January Evening Slot
+4
-1
Out of Syllabus
Two Carnot engines A and B are operated in series. The first one, A, receives heat at T1 (= 600 K) and rejects to a reservoir at temperature T2. The second engine B receives heat rejected by the first engine and, in tum, rejects to a heat reservoir at T3 (=400 K). Calculate the temperature T2 if the work outputs of the two engines are equal :
A
600 K
B
400 K
C
300 K
D
500 K
4
JEE Main 2019 (Online) 9th January Evening Slot
+4
-1
A 15 g mass of nitrogen gas is enclosed in a vessel at a temperature 27oC. Amount of heat transferred to the gas, so that rms velocity of molecules is doubled, is about : [Take R = 8.3 J/K mole]
A
0.9 kJ
B
6 kJ
C
10 kJ
D
14 kJ
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