Thermodynamics Test

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Thermodynamics Test - 29

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Weekly Quiz Competition

Question 1
1 / -0

Which heat depends on the direction of current?

A
Joule heat

B
Peltier heat

C
Thompson effect

D
None of these

Solution

In Peltier effect, heat loss and heat gain depends upon the direction of current. A typical Peltier heat pump involves multiple junction in series in which direction of current is important.
Question 2
1 / -0

Molar specific heat at constant pressure of oxygen is

A
29 J

B
43 J

C
64 J

D
81 J
Question 3
1 / -0

Match the following.
I Isothermal process $$1$$ $$\Delta Q=0$$
II Isobaric process $$2$$ $$\Delta V=0$$
III Isochoric process $$3$$ $$\Delta P=0$$
IV Adiabatic process $$4$$ $$\Delta T=0$$

A
I-$$4$$, II-$$3$$, III-$$2$$, IV-$$1$$

B
I-$$3$$, II-$$2$$, III-$$1$$, IV-$$4$$

C
I-$$1$$, II-$$2$$, III-$$3$$, IV-$$4$$

D
I-$$4$$, II-$$2$$, III-$$3$$, IV-$$1$$

E
I-$$1$$, II-$$4$$, III-$$2$$, IV-$$3$$

Solution

I-$$4$$ ($$\because$$ In isothermal process, temperature remains constant)
II-$$3$$ ($$\because$$ In isobaric process, pressure remains constant)
III-$$2$$ ($$\because$$ In isochoric process, volume remains constant)
IV-$$1$$ ($$\because$$ In adiabatic process, total heat of the system remains constant)
Question 4
1 / -0

The process in which the heat is not transferred from one state to another, is:

A
isothermal process

B
adibatic process

C
isobaric process

D
isochoric process

Solution
Question 5
1 / -0

The pressure and density of a diatomic gas$$\left ( \gamma =\dfrac{7}{5} \right )$$ change adiabatically from $$(P_1,\rho_1)$$ to $$(P_2,\rho_2)$$. If $$\dfrac{\rho _{2}}{\rho _{1}}=32 ,$$ then $$\dfrac{P _{2}}{P _{1}}$$ should be

A
126

B
128

C
146

D
124

Solution

For an adiabatic process,
$$PV^{\gamma }=$$constant
$$P{\rho }^{-\gamma }=$$constant
$$\displaystyle \dfrac {P_2}{P_1}={(\dfrac {\rho _1}{\rho _2})}^{-\gamma }={(\dfrac {1}{32})}^{-7/5}=(32)^{7/5}=128$$
Option B.
Question 6
1 / -0

Heat is absorbed by a body, but its temperature does not increase. Which of the following statement explains the phenomena?

A
Only K.E. of vibration increases

B
Only P.E. of inter molecular force changes

C
No increase in internal energy takes place

D
Increase in K.E. is balanced by decrease in P.E.

Solution

The heat energy necessary to bring about the change of state that does not appear externally is called the latent heat.
During the change of state, the energy supplied (latent heat) breaks up the inter-molecular interactions and only the potential energy stored of these inter-molecular force changes. So, the temperature remains constant until all the interactions are completely disrupted.

For example during the change of state from ice to water heat is absorbed but the temperature does not rise.
Question 7
1 / -0

The adiabatic and isothermal elasticities $$B_\phi $$ and $$B_\theta $$ are related as :

A
$$\dfrac{B_{\phi } }{B_{\theta } }=\gamma $$

B
$$\dfrac{B _{\theta }}{B_{\phi } }=\gamma $$

C
$$B_{\phi }-B_{\theta }=\gamma $$

D
$$B_{\theta }-B_{\phi }=\gamma $$

Solution

Bulk modulus= $$B= -V $$ ($$\dfrac { dP }{ dV } $$)
For adiabatic process, $$\dfrac { dP }{ dV } = -\dfrac { \gamma P }{ V }$$
Thus, $$B_{\phi }= \gamma P$$
For isothermal process, $$\dfrac { dP }{ dV } = -\dfrac { P }{ V } $$
Thus, $$B_{\theta }= P$$
So, $$\dfrac{B_{\phi }}{B_{\theta }}= \gamma $$
Question 8
1 / -0

Consider the following two statements and choose the correct answer :
A) If heat is added to a system its temperature must always increase
B) If positive work is done by a system in thermodynamic process its volume must increase.

A
Both (A) and (B) are correct.

B
(A) is correct but (B) is wrong.

C
(A) is wrong but (B) is correct.

D
Both (A) and (B) are wrong.

Solution

If heat is added to a system, the system can do work without changing its internal energy (isothermal process). Hence, statement 1 is false.

Positive work means gas is expanding. Hence, it's volume must increase.
Question 9
1 / -0

A fixed amount of dry air at temperature of $$27^{o}C$$ is compressed to $$\cfrac{1}{9}th$$ of original volume. Its final temperature is $$\left ( \gamma =1.5 \right )$$

A
$$627^{o}C$$

B
$$600^{o}C$$

C
$$158^{o}C$$

D
$$527^{o}C$$

Solution

In an adiabatic process,
$$TV^{\gamma -1}=$$constant
$$T_1V^{\gamma -1}_1=T_2V^{\gamma -1}_2$$
$$\displaystyle T_2=T_1\times \dfrac {V^{\gamma -1}_1}{V^{\gamma -1}_2}=300\times {(\dfrac {1}{1/9})}^{1.5-1}=300(3)=900K=627^oC$$
Option A.
Question 10
1 / -0

An isothermal process is :

A
slow process

B
quick process

C
very quick process

D
both A & B

Solution

An isothermal process is a process in which the temperature remains constant: $$ \Delta T = 0$$. This typically occurs when a system is in contact with an outside thermal reservoir , and the change occurs slowly enough to allow the system to continually be in thermal equilibrium with the reservoir through heat exchange.
Hence it's a slow process.

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Re-Attempt Weekly Quiz Competition

I	Isothermal process	$$1$$	$$\Delta Q=0$$
II	Isobaric process	$$2$$	$$\Delta V=0$$
III	Isochoric process	$$3$$	$$\Delta P=0$$
IV	Adiabatic process	$$4$$	$$\Delta T=0$$

Thermodynamics Test - 29

Result

Thermodynamics Test - 29

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SHARING IS CARING

Question 1

Joule heat

Peltier heat

Thompson effect

None of these

Solution

Question 2

29 J

43 J

64 J

81 J

Question 3

I-$$4$$, II-$$3$$, III-$$2$$, IV-$$1$$

I-$$3$$, II-$$2$$, III-$$1$$, IV-$$4$$

I-$$1$$, II-$$2$$, III-$$3$$, IV-$$4$$

I-$$4$$, II-$$2$$, III-$$3$$, IV-$$1$$

I-$$1$$, II-$$4$$, III-$$2$$, IV-$$3$$

Solution

Question 4

isothermal process

adibatic process

isobaric process

isochoric process

Solution

Question 5

126

128

146

124

Solution

Question 6

Only K.E. of vibration increases

Only P.E. of inter molecular force changes

No increase in internal energy takes place

Increase in K.E. is balanced by decrease in P.E.

Solution

Question 7

$$\dfrac{B_{\phi } }{B_{\theta } }=\gamma $$

$$\dfrac{B _{\theta }}{B_{\phi } }=\gamma $$

$$B_{\phi }-B_{\theta }=\gamma $$

$$B_{\theta }-B_{\phi }=\gamma $$

Solution

Question 8

Both (A) and (B) are correct.

(A) is correct but (B) is wrong.

(A) is wrong but (B) is correct.

Both (A) and (B) are wrong.

Solution

Question 9

$$627^{o}C$$

$$600^{o}C$$

$$158^{o}C$$

$$527^{o}C$$

Solution

Question 10

slow process

quick process

very quick process

both A & B

Solution

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