This
post covers the repeated 2 marks questions asking from the Anna University for
the subject, ME6301 Engineering Thermodynamics. Here unit wise repeated 2 marks
with answers given for the benefits of Mechanical Engineering students.
Unit
I BASIC CONCEPTS AND FIRST LAW
Part-A
(2 Marks with Answers)
1.
What is meant by thermodynamic system? How do you classify it?
It is defined as any space or matter or group of
matter where the energy transfer or energy conversions are studied. It is
classified into 3 types as follows
(i)
Open System
(ii)
Closed system
(iii)
Isolated System
2.
Distinguish open system and closed systems.
S.No
|
Open system
|
Closed system
|
1
|
Mass
transfer takes place
|
There
is no mass transfer
|
2
|
In
addition to the heat and work transfer
|
Only
heat and work will transfer
|
3
|
System
boundary may or may not change.
|
System
boundary is fixed one
|
4
|
Ex: wind mill, Air Compressor,
Boiler
|
Ex: Mixture of ice and water in a
metal container, Piston and cylinder arrangement, Thermal Power plant
|
3.
Define an Isolated system.
In
this system, total energy remains constant. There is no heat, work and mass
transfer takes place. Isolated system is not affected by surroundings.
Ex:
Entire Universe
4.
Define specific capacity at constant volume.
It is
defined as the amount of heat energy required raising or lowering the temperature
of unit mass of the substance through one degree when the volume kept constant.
It is denoted by Cv.
5.
Define specific capacity at constant pressure.
It is
defined as the amount of heat energy required raising or lowering the temperature
of unit mass of the substance through one degree when the pressure kept
constant. It is denoted by Cp.
6.
Define intensive and extensive properties.
Intensive properties:
The properties which are independent of the mass of
the system are called intensive properties.
Ex:
Pressure, Temperature, Specific volume etc.,
Extensive properties:
The properties which are dependent of the mass of
the system are called extensive properties.
Ex:
Total energy, total volume, weight etc.,
7.
What do you understand by equilibrium of a system?
When a system remains in equilibrium
state, it should not undergo any changes on its own accord.
8.
When a system is said to be in “Thermodynamic equilibrium”?
When
a system is in thermodynamic equilibrium, it should satisfy the following three
conditions.
(i)
Mechanical Equilibrium- Pressure remains
constant
(ii)
Thermal Equilibrium- Temperature remains
constant
(iii)
Chemical Equilibrium- There is no
chemical reaction
9. State zeroth law of
thermodynamics.
It states that when two systems are
separately in thermal equilibrium with a third system, then they themselves is
in thermal equilibrium with each other.
10. State first law of
thermodynamics.
It states that “when a system
undergoes a cyclic process, then the net heat transfer is equal to the net work
transfer”.
It may be stated, “The heat and work
are mutually convertible”.
Clich here Previous Anna University questions May 2015
Click here Anna University questions Nov/Dec 2012
Click here Anna University questions Nov/Dec 2012
11. Compare microscopic and
macroscopic approaches.
S.No
|
Microscopic
Approach
|
Macroscopic
Approach
|
1.
|
Many
coordinates are required to describe the system properly.
|
A few
coordinates are enough to describe the system properly.
|
2.
|
The properties
of matter of the individual molecule at a given instant or at a particular
time are studied.
|
The behavior of
the total system in terms of properties is studied.
|
3.
|
Special assumptions
are required for describing the matter in microscopic coordinates.
|
No need of
Special assumptions is required for describing the matter in macroscopic coordinates.
|
4.
|
More complex
mathematical equations are used for the analysis.
|
It requires
far fewer mathematical complications.
|
12.
List the limitations of first law of thermodynamics.
(i) It does not specify
the direction of flow of heat and work.
(ii) The heat and work
are mutually convertible. The work can be converted fully into heat energy but
heat cannot be converted fully into mechanical work.
(iii) Perpetual Motion Machine (PMM-1) is a machine
which delivers work continuously without any input. Thus, the machine violates
first law of thermodynamics.
13.
What is meant by reversible and irreversible process?
A process is said to be reversible, it should
trace the same path in the reverse direction when the process is reversed, and
it is possible only when the system passes through a continuous series of
equilibrium state.
If a
system does not pass through continuous equilibrium state, then the process is
said to be irreversible.
14.
Differentiate Path function and Point function.
S.No
|
Path function
|
Point function
|
1.
|
The
quantity which is dependent on the process or path followed by the system
|
The
quantity which is independent on the process or path followed by the system
|
2.
|
Ex: Heat
transfer, Work transfer
|
Ex: Pressure,
Volume, Temperature
|
3.
|
It
considers the direction of processes.
|
It
does not considers the direction of processes.
|
4.
|
The
cyclic integral of a path function is non zero.
|
The
cyclic integral of a point function is zero.
|
15.
What is Quasi-static process?
The process is said to
be quasi-static, if it proceeds infinitesimally slow and follows continuous
series of equilibrium states. Therefore, it may b a reversible process.
16.
Define the term enthalpy.
The combination of
internal energy and flow energy is known as enthalpy of the system
Mathematically, Enthalpy (H)=U + pV
Where U be the internal energy in kJ
P be
the pressure in kPa
V be the volume in m3
17. What are the conditions for
steady flow process?
(i) The streams of material crossing
the control surface must not change their state or flow rate with time.
(ii) Each point within the control
volume must not change its state with time or only cyclic state variation
occurs.
(iii)The heat and work
transfer rates must not change with time or the mean rates in this case of
cyclic behavior must not change.
18.
Identify any four reasons for irreversibility in a process. (AU April' 12)
(i) Lack
of equilibrium
(ii) Free
expansion
(iii)
Heat transfer through a finite temperature difference.
(iv) Dissipative effects
(v)
Lack of pressure equilibrium within the interior of the system.
For more question bank with answers, Lecture notes, Previous years Anna University questions were uploaded in annaunivstudymaterials.blogspot.com
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