10.1 Multiple choice questions.
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1.
When
two bodies are made at thermal contact having the same temperature then they
are at: |
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(a)
Physical equilibrium |
(b)
Thermal equilibrium |
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(c)
Mechanical equilibrium |
(d)
Chemical equilibrium |
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2.
Normal
temperature of a man body is 98.6°F while its atmosphere temperature is 84.
6° F. What will be the temperature of the dead body in such atmosphere |
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(a)
86.4°F |
(b)
98.6°F |
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(c)
92.5°F |
(d)
185°F |
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3.
When
the system is expanded by adding heat energy then the work done is: |
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(a)
Positive and on the system |
(b)
Negative and on the system |
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(c)
Positive and by the system |
(d)
Negative and by the system |
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4.
Which
substance possesses the largest internal energy at t°C |
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(a)
Solid |
(b)
Liquid |
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(c)
Gas |
(d)
All of these |
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5.
Internal
energy of a substance is defined in terms of |
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(a)
P and V |
(b)
P and T |
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(c)
T and V |
(d)
P, V and T |
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6.
The
ratio between work done and heat energy is equal to: |
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(a)
Adiabatic constant |
(b)
Joule’s constant |
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(c)
Specific heat constant |
(d)
Real gas constant |
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7.
A
system which transfers neither mass not energy is called; |
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(a)
Open system |
(b)
Close system |
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(c)
Isolated system |
(d)
Non-cyclic system |
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8.
First
law of thermodynamics is based upon law of conservation of; |
|
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(a)
Mass |
(b)
Energy |
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(c)
Momentum |
(d)
Charges |
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9.
A
process in which all the heat energy is used for increasing internal energy
of the system is known as: |
|
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(a)
Isobaric |
(b)
Isochoric |
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(c)
Isothermal |
(d)
Adiabatic |
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10. In which process the internal energy is used
for doing work: |
|
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(a)
Isobaric |
(b)
Isochoric |
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(c)
Isothermal |
(d)
Adiabatic |
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11. Specific heat of a gas in an isothermal
process is: |
|
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(a)
Zero |
(b)
Remains constant |
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(c)
Negative |
(d)
Infinite |
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12. A process in which the system remains at
thermal equilibrium is known as: |
|
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(a)
Isobaric |
(b)
Isochoric |
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(c)
Isothermal |
(d)
Adiabatic |
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13. The value of adiabatic constant for
mono-atomic gas is |
|
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(a)
1.40 |
(b)
1.44 |
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(c)
1.60 |
(d)
1.66 |
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14. The efficiency of a heat engine will be 100%
when. |
|
|
(a)
Engine takes huge amount of heat from source |
(b)
Engine exhaust a very small amount of heat from sink |
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(c)
The temperature of cold reservoir is 0°C |
(d)
The temperature of cold reservoir is 0 K |
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15. Second law of thermodynamics provides the
proper direction of; |
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(a)
Temperature |
(b)
Force |
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(c)
Pressure |
(d)
Flow of heat |
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16. A device which converts mechanical energy
into heat energy is known as: |
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(a)
Heat engine |
(b)
Carnot Engine |
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(c)
Refrigerator |
(d)
Turbine |
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17. Entropy of a reversible process; |
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(a)
Decreases |
(b)
Increases |
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(c)
Infinite |
(d)
Zero |
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18. Entropy remains constant in the process of; |
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(a)
Isochoric |
(b)
Isobaric |
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(c)
Isothermal |
(d)
Adiabatic |
Answers
- (b) Thermal equilibrium
- (a) 86.4°F
- (c) Positive and by the system
- (c) Gas
- (c) T and V
- (b) Joule’s constant
- (c) Isolated system
- (b) Energy
- (b) Isochoric
- (d) Adiabatic
- (a) Zero
- (c) Isothermal
- (d) 1.66
- (d) The temperature of cold reservoir is 0 K
- (d) Flow of heat
- (a) Heat engine
- (b) Increases
- (d) Adiabatic
ans.
When two or more system are at the same temperature and there is no net heat between them then
the system is said to be perfect thermal equilibrium.
7. Why the measurement of molar specific heat is being preferred than
specific heat?
ans.
Because one mole of any substance contains the same number of
molecules which is more preferred than specific heat.
9. What is the difference between reversible and irreversible process?
ans.
A reversible process is a process that can be reversed to
return the system and its surrounding to their original states, with no
generation of entropy. For example, the conversion of the ice into water then
water into ice. While irreversible process generate entropy in the system and
can’t be retraced in the exact order. For example, flow of heat from hot body
to a cold body is an irreversible process.
14. What will be the work done of a system when it’s hot and cold reservoirs
are at same temperature?
ans.
If the hot and cold reservoir of a system are at the same
temperature, then no work is done because no temperature difference and no heat
transfer can occur.
10.3 Numerical problems
5. A mechanical engineer develops an engine, working between 327°C and 27°C
and claims to have an efficiency of 50%. Does he claim correctly? Explain.
9. How much work does on ideal Carnot refrigerator require to remove 1 J of energy from helium at 4k and reject this thermal energy to a room temperature 293 K environment.
