1
JEE Main 2015 (Offline)
MCQ (Single Correct Answer)
+4
-1
Change Language
A solid body of constant heat capacity $$1$$ $$J/{}^ \circ C$$ is being heated by keeping it in contact with reservoirs in two ways:
$$(i)$$ Sequentially keeping in contact with $$2$$ reservoirs such that each reservoir
$$\,\,\,\,\,\,\,\,$$supplies same amount of heat.
$$(ii)$$ Sequentially keeping in contact with $$8$$ reservoirs such that each reservoir
$$\,\,\,\,\,\,\,\,\,\,$$supplies same amount of heat.
In both the cases body is brought from initial temperature $${100^ \circ }C$$ to final temperature $${200^ \circ }C$$. Entropy change of the body in the two cases respectively is :
A
$$ln2, 2ln2$$
B
$$2ln2, 8ln2$$
C
$$ln2, 4ln2$$
D
$$ln2, ln2$$
2
JEE Main 2015 (Offline)
MCQ (Single Correct Answer)
+4
-1
Change Language
Consider an ideal gas confined in an isolated closed chamber. As the gas undergoes an adiabatic expansion, the average time of collision between molecules increases as $${V^q},$$ where $$V$$ is the volume of the gas. The value of $$q$$ is: $$\left( {\gamma = {{{C_p}} \over {{C_v}}}} \right)$$
A
$${{\gamma + 1} \over 2}$$
B
$${{\gamma - 1} \over 2}$$
C
$${{3\gamma + 5} \over 6}$$
D
$${{3\gamma - 5} \over 6}$$
3
JEE Main 2015 (Offline)
MCQ (Single Correct Answer)
+4
-1
Change Language
Consider a spherical shell of radius $$R$$ at temperature $$T$$. The black body radiation inside it can be considered as an ideal gas of photons with internal energy per unit volume $$u = {U \over V}\, \propto \,{T^4}$$ and pressure $$p = {1 \over 3}\left( {{U \over V}} \right)$$ . If the shell now undergoes an adiabatic expansion the relation between $$T$$ and $$R$$ is:
A
$$T\, \propto {1 \over R}$$
B
$$T\, \propto {1 \over {{R^3}}}$$
C
$$T\, \propto \,{e^{ - R}}$$
D
$$T\, \propto \,{e^{ - 3R}}$$
4
JEE Main 2014 (Offline)
MCQ (Single Correct Answer)
+4
-1
The pressure that has to be applied to the ends of a steel wire of length $$10$$ $$cm$$ to keep its length constant when its temperature is raised by $${100^ \circ }C$$ is: (For steel Young's modulus is $$2 \times {10^{11}}\,\,N{m^{ - 2}}$$ and coefficient of thermal expansion is $$1.1 \times {10^{ - 5}}\,{K^{ - 1}}$$ )
A
$$2.2 \times {10^8}\,\,Pa$$
B
$$2.2 \times {10^9}\,\,Pa$$
C
$$2.2 \times {10^7}\,\,Pa$$
D
$$2.2 \times {10^6}\,\,Pa$$
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