Thermodynamics Test

Result

Thermodynamics Test - 79

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Weekly Quiz Competition

Question 1
1 / -0

When bulb of initial resistance $$R_{0}$$ is switch on its resistance increase due to heat production. Assuming initial temperature of bulb is $$0^{o}C$$. and temperature coefficient of bulb is $$\alpha$$. After what time its temperature will become $$T$$. (Heat capacity of bulb is $$'c'$$)

A
$$\dfrac { \left( { e }^{ \alpha T }-1 \right) .{ R }_{ 0 }c }{ { \varepsilon }^{ 2 }\alpha } $$

B
$$\dfrac 2{ \left( { e }^{ \alpha T }-1 \right) .{ R }_{ 0 }c }{ { \varepsilon }^{ 2 }\alpha } $$

C
$$\dfrac { \left( { e }^{ \alpha T }-1 \right) .{ R }_{ 0 }c }{ { 2\varepsilon }^{ 2 }\alpha } $$

D
$$\dfrac { \left( { e }^{ \alpha T }+1 \right) .{ R }_{ 0 }c }{ { \varepsilon }^{ 2 }\alpha } $$

Solution
Question 2
1 / -0

If $$C _ { V }$$ for an ideal gas is given by $$C _ { V } = 3 + 2 T, $$ where $$T$$ is the absolute temperature of the gas, then the equation of the adiabatic process for this gas is

A
$$\mathrm { VT } ^ { 2 } =$$ Constant

B
$$\mathrm { VT } ^ { 2 } \mathrm { e } ^ { 2 \mathrm { T } } =$$ Constant

C
$$\mathrm { VT } ^ { 3 } \mathrm { e } ^ { - 2 \mathrm { T } } =$$ Constant

D
$$\mathrm { VT } ^ { 3 } \mathrm { e } ^ { 2 \mathrm { T } } =$$ Constant

Solution
Question 3
1 / -0

Two moles of an ideal monoatomic gas occupies a volume V at $$27^0C$$. The gas expands adiabatically to a volume 2 V. Calculate (a) the final temperature of the gas and (b) change in its internal energy.

A
(a) 195 K
(b) 2.7 kJ

B
(a) 189 K
(b) 2.7 kJ

C
(a) 195 K
(b) -2.7 kJ

D
(a) 189 K
(b) -2.7 kJ

Solution
Question 4
1 / -0

$$n$$ moles of a gas expands from volume $${V_1}\;to\;{V_2}$$ at constant temperature $$T$$. The work done by the gas is

A
$$nRT (\dfrac {V_1}{V_2})$$

B
$$nRT (\dfrac {V_2}{V_1})$$

C
$$nRT (\dfrac {2V_1}{V_2})$$

D
$$nRT (\dfrac {2V_2}{V_1})$$

Solution
Question 5
1 / -0

Icc of water at $$ 100^o C $$ is given 540 cal of heat and the steam formed accupies 167 Icc at the atmospheric pressure. Then workdone against atmospheric pressure in this process is nearly.

A
540 cal

B
500 cal

C
40 cal

D
100 cal

Solution

$$\text { Change in vol. } =(1671-1) c c \\$$
$$=1670 \times 10^{-6} \mathrm{~m}^{3} \\$$
$$\text { Atmospheric pressure:- } 10^{5} \mathrm{pa} \text { . } \\$$
$$\text { Net work done } =P \Delta V \\$$
$$=10^{5} \times 1670 \times 10^{-6} \\$$
$$=167 \mathrm{~J}$$

$$=39.78 \mathrm{cal} [1 \mathrm{cal}=4.2 \mathrm{~J}]$$

Answer $$1-(\mathrm{C})$$ $$40 cal$$
Question 6
1 / -0

The P - V diagram of a system undergoing a thermodynamic process is shown in figure. Work done by the system in going from $$A \rightarrow B \rightarrow C$$ is 30 J and 40 J heat is given to the system. The change in internal energy of the gas if the gas is directly taken from A to C is

A
10 J

B
70 J

C
84 J

D
134 J

Solution

For process $$A \to B \to C$$
$$\Delta u = \Delta \theta - \Delta \omega $$
$$ = 40 - 30$$
$$ = 10J$$
$$A \to C$$
$$\Delta u = 10J$$
Hence$$,$$ option $$(A)$$ is correct$$.$$
Question 7
1 / -0

The following sets of values for $$C_{v}$$ and $$C_{p}$$ of gas has been reported by different students. The units are $$cal/gm-mole-K$$. Which of these sets is most reliable

A
$$C_{v}=3,C_{p}=5$$

B
$$C_{v}=4,C_{p}=6$$

C
$$C_{v}=3,C_{p}=2$$

D
$$C_{v}=3,C_{p}=4.2$$

Solution
Question 8
1 / -0

A gas is compressed at a constant pressure of $$50 N/{ m }^{ 2 }$$ from a volume $$10{ m }^{ 3 }$$ to a volume of $$6 { m }^{ 3 }$$. $$100 J$$ of heat is added to the gas then its internal energy

A
Increasing by 400 J

B
Increasing by 300 J

C
Decreasing by 400 J

D
Decreasing by 200 J

Solution
Question 9
1 / -0

A monoatomic gas is suddenly compressed to 1/8 th of its initial volume adiabactically. The ratio of its final pressure to initial pressure is (y=5/3)

A
32

B
40/3

C
24/5

D
8

Solution
Question 10
1 / -0

P-V graph for a cyclic process is as shown. V-T graph for the process is [AB is isothermal and CA is an adiabatic process]

A

B

C

D

Solution