1
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
In a dilute gas at pressure P and temperature T, the mean time between successive collisions of a molecule varies with T as :
A
$$\sqrt T$$
B
T
C
$${1 \over T}$$
D
$${1 \over {\sqrt T }}$$
2
JEE Main 2020 (Online) 6th September Evening Slot
+4
-1
Three rods of identical cross-section and lengths are made of three different materials of thermal conductivity K1 , K2 and K3 , respecrtively. They are joined together at their ends to make a long rod (see figure). One end of the long rod is maintained at 100oC and the other at 0oC (see figure). If the joints of the rod are at 70oC and 20oC in steady state and there is no loss of energy from the surface of the rod, the correct relationship between K1 , K2 and K3 is :
A
K1 : K3 = 2 : 3,
K2 : K3 = 2 : 5
B
K1 < K2 < K3
C
K1 : K2 = 5 : 2,
K1 : K3 = 3 : 5
D
K1 > K2 > K3
3
JEE Main 2020 (Online) 6th September Morning Slot
+4
-1
Molecules of an ideal gas are known to have three translational degrees of freedom and two rotational degrees of freedom.The gas is maintained at a temperature of T. The total internal energy, U of a mole of this gas, and the value of
$$\gamma \left( { = {{{C_p}} \over {{C_v}}}} \right)$$ are given, respectively by:
A
U = $${5 \over 2}RT$$ and $$\gamma = {7 \over 5}$$
B
U = 5RT and $$\gamma = {6 \over 5}$$
C
U = 5RT and $$\gamma = {7 \over 5}$$
D
U = $${5 \over 2}RT$$ and $$\gamma = {6 \over 5}$$
4
JEE Main 2020 (Online) 5th September Evening Slot
+4
-1
Two different wires having lengths L1 and L2, and respective temperature coefficient of linear expansion $$\alpha$$1 and $$\alpha$$2, are joined end-to-end. Then the effective temperature coefficient of linear expansion is :
A
$$2\sqrt {{\alpha _1}{\alpha _2}}$$
B
$$4{{{\alpha _1}{\alpha _2}} \over {{\alpha _1} + {\alpha _2}}}{{{L_2}{L_1}} \over {{{\left( {{L_2} + {L_1}} \right)}^2}}}$$
C
$${{{\alpha _1} + {\alpha _2}} \over 2}$$
D
$${{{\alpha _1}{L_1} + {\alpha _2}{L_2}} \over {{L_1} + {L_2}}}$$
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