Different types of pressure

Fluid pressure -:  Pressure is transmitted with equal intensity in all directions and act normal to any plane is known as fluid pressure .

Difference in pressure between any two points at different level in a liquid is equal to = unit weight of liquid × difference in elevation. 

Gauge pressure -: It is equal to unit weight of the liquid multiplied by the height of the desired point above free surface . Gauge pressure represents pressure above atmospheric pressure. 

Bar pressure -: Gauge pressure in bar is generally obtained by dividing the gauge pressure in Pascal Z by 10^5 .

Pressure head-: Pressure head 'h' represent the height of a volumn of homogeneous fluid that will produce a given intensity of the pressure   ( h = p / ρg ) .

Property of a system

Property represents any observable chara-cteristics of the system.  Property of a system depends only on its state , irrespective of how that state was attained. 

Intensive property -: If a property of  a system does not depend upon it's mass , it is intensive property. For example,  pressure, temperature, density,  etc .

Extensive property -: when the property of any system is depend upon the mass it is called extensive property. For example enthalpy , volume, etc .

 

If a given quantity depend on two para-meters is connected such that these para-meters are connected by a line path , then the quantity is not a property . if an given quantity is an exact differential,  it is pro-perty ,otherwise no .

Free energy and free Enthalpy

Free energy -: Free energy ( or Helmholtz function) is defined as  f = u - Ts .

It is equal to the work during a constant- volume isothermal reversible nonflow process .

Free Enthalpy -: Free enthalpy ( or Gibbs function ) is defined as  g = h - Ts

Where , u = internal energy  h = enthalpy ,      T = temperature, s = entropy 

Gibbs function is of particular importance in processes where chemical changes occur. For reversible isothermal steady flow pro-cesses or for reversible constant- pressure isothermal nonflow processes , change in free energy is equal to net work .

Fluid mechanics MCQ-07

Q.1 Gas is a ______ fluid. 

A. Compressible 

B. Non - compressible 

C. Viscous 

D. Non- viscous 

Ans-: A

Q.2 The ratio of the mass of a body to the mass of an equal volume of a substance taken as a standard known as ___.

A. Kinematic viscosity 

B. Relative density 

C. Density

D. Viscosity 

Ans-:B

Q.3 The rise or fall of a liquid in a capillary tube caused by the surface tension called ?

A. Rise of liquid 

B. Fall of liquid 

C. Capillarity 

D. A+B

Ans-: C

Q.4 The fluid such as air for which the density is not a single-valued function of the pressure is known as ?

A. Barotropic fluid 

B. Nonbarotropic fluid 

C. Real fluid 

D. Perfect fluid 

Ans-:B

Q.5 Buoyant force is equal to _____.

A. Force exerted by body

B. Volume of liquid displaced 

C. Force exerted in body

D. Weight of the body 

Ans-: B

Q.6 Stanton tube is used to measure which of the following?

A. Shear strain

B. Shear stress in fluid 

C. Shear strain in fluid 

D. Pressure of fluid 

Ans-: B

Q.7 What is the density of air ?

A. 11.2 kg/m^-3

B. 1.24 kg/m^3

C. 1.24 kg/m^-3

D.  12.4 kg/m^3

Ans-: C

Q.8 Whether stream function exists for which type of flow?

A. Uniform flow 

B. One dimensional flow 

C. Turbulent flow 

D. Two dimensional flow 

Ans-: D

Q.9 What is the value of density of mercury?

A. 1360 kg/m^-3

B. 13600 kg/m ^-3

C. 14000 kg/m^3

D. 13560 kg/m^-3

Ans-: B

Q.10 The square root of ratio inertia force to gravity force is called ?

A. Real number

B. Froude number

C. Reynolds number 

D. None of these 

Ans-: B

Q.11 When specific mass flow is not able to take place in a pipe line us called ?

A. More pressure in pipe line 

B. Choking in pipe line 

C. Disturbance in flow

D  None of these 

Ans-: B

Q.12 Maning's formula is used to measure?

A. Viscosity of fluid

B. Velocity if fluid in pipe 

C. Pressure of fluid in a pipe 

D. Surface tension 

Ans-: B

Q.13 Velocity potential is which type of quantity.

A. Dimensional

B. Scalar

C. Non - scalar

D. None of the above 

Ans-: B

Q.14 In open channel maximum velocity occurs at ______.

A. Center of the channel 

B. Top of the channel

C. Near Bottom of the channel 

D. First point of the channel 

Ans-: C

Q.15 Velocity is zero at which point ?

A. Stagnation point 

B. Triple point 

C. Critical point

D. None of the above 

Ans-: A

Fluid mechanics MCQ-06

Q.1 Center of pressure on a inclined plane is ________ .

A. Above the centroid

B. Below the centroid 

C. At the centroid 

D. None of these 

Ans-: B

Q.2 The unit of dynamic viscosity is ___.

A. M^2 per second 

B. Newton sec per m^2

C. Newton sec per m^3

D. Kg sec / meter

Q.3 Spherical shape of the rain drop are due to ___.

A. Surface tension 

B. Viscosity 

C. Density 

D. None of the above 

Ans-: A

Q.4 The inside and outside pressure diffe-rence between inside and outside of water drop is ______.

A. P = T/r

B. P = 2T/r

C. P = T×r

D. 0

Ans-: B

Q.5 Which devise is used to measure very low pressure?

A. Thermometer 

B. Manometer

C. Piezometer

D. None of these 

Ans-: C

Q.6 Surface tension of water at 20°C is ___.

A. 60.71

B. 60.61

C. 52.23

D. 79.61

Ans-: A

Q.7 Due to balance of the body weight and the buoyancy force a floating body ______.

A. Submerged in water 

B. Partially submerged 

C. Floating 

D. None of these 

Ans-: B

Q.8 General energy equation holds for which type of flow?

A. Laminar flow 

B. Uniform flow 

C. Non- uniform flow 

D. Steady flow 

Ans-: C

Q.9 Hydraulic grade line may be above or below the centre line of conduit.

A. Yes 

B. No 

C. At specific pressure 

D. None of these 

Ans-: A

Q.10 During the opening of a valve in a pipe line ,the flow is ______.

A. Steady 

B. Unsteady 

C. Uniform 

D. Turbulent 

Ans-: B

Fluid mechanics MCQ -05

Q.1 For which type of flow Bernoulli's theo-rem is applicable?

A. Turbulent flow 

B. Laminar flow 

C. Perfect incompressible fluid flowing in a continuous stream

D. Normal flow

Ans-: C

Q.2 Velocity of flow in open channel is determined by which equation?

A. Chezy's equation 

B. Bernoulli equation 

C. Motion equation 

D. None of these 

Ans-: A

Q.3 The magnitude of the water hammer is depend on the _______ .

A. Rate of stoppage of flow

B. Length of the pipe

C. Elastic properties of pipe material 

D. All of the above 

Ans -: D

Q.4 At the center of the pipe velocity of fluid particles is _____.

A. Zero

B. Maximum 

C. Minimum 

D. One

Ans-: B

Q.5 100 kN/m^2 is equal to _____ .

A. 100 mm of water column

B. 10 mm of water column

C. 20 mm of water column 

D. 200 mm of water column

Ans-: B

Q.6 The flow in venturiflume take place at ___.

A. Vacuum 

B. Atmospheric pressure 

C. High temperature 

D. High pressure 

Ans-: B

Q.7 Bernoulli theorem deals with the conser-vation of hydraulic pressure .

A. Yes 

B. No 

C. At high pressure 

C. At 0° C 

Ans-: A

Q.8 The volume of water which flows thro-ugh a section of a channel per second is known as __.

A. Flow rate

B. Discharge 

C. Stream flow 

D. None of these 

Ans-: B

Q.9 The pattern obtained by the intersection of stream lines and potential lines is called _.

A. Flow pattern

B. Flow design

C. Flow net

D. Flow rate 

Ans-: C

Q.10 The force exerted on a body by a static fluid in which it is submerged or floating called ______ force .

A. Buoyant force

B. Drag force

C. Impact load 

D. Submerged force

Ans-: A

Fluid mechanics MCQ-04

Q.1 which instrument is used to measure flow ?

A. Thermometer 

B. Rotameter

C. Raynold's meter

D. Barometer

Ans-: B

Q.2 Hydraulic jump is the example of which type of flow ?

A. Uniform flow 

B. Steady flow 

C. Non- uniform flow 

D. Turbulent flow 

Ans-: C

Q.3 Any obstruction of a stream flow over which water flows can be called ___.

A. Weir

B. Spillway

C. Water hammer

D. None of these 

Ans-: A

Q.4 water hammer is caused due to sudden stoppage of ____ .

A. Water contain in a tank

B. Water flow in a pipe 

C. Water flow through open channel 

D. All of the above 

Ans-: B

Q.5 _____ are used to relieve the pipe line of excessive pressure. 

A. Dam

B. Surge tank 

C. Hydraulic dam

D. None of these 

Ans-: B

Q.6 which device is used for measuring the rate of flow of a liquid through a small channel?

A. Notch

B. Rotameter 

C. Manometer

D. NOT

Ans-: A

Q.7 which of the following is measured by the pitot tube?

A. Pressure 

B. Flow

C. Discharge 

D. Velocity 

Ans-: D

Q.8 the upper surface of the weir over which water flows ______.

A. Vein

B. Sill

C. Nappe

D. Weir top surface 

Ans-: B

Q.9 specific gravity of fluid is determined by 

A. Hydrometer

B. Rotameter 

C. Manometer

D. None of these 

Ans-: A

Q.10 An idel fluid is __.

A. Frictionless 

B. Incompressible 

C. Very viscous 

D. A+B

Ans-: D

Hydraulic jump and water hammer

Hydraulic jump -:It is occurs when rapidly flowing of liquid in an open channel sudde- nly changes to a slowly flowing stream with a large cross - section area and sudden rise in elevtaion of liquid surface occurs. It is a very effective device for creating irrever- sibilities and commonly used at the end of chutes or the bottom of spillway to destroy much of kinetic energy in flow.this is the example of steady non- uniform flow. 

Water hammer-: water hammer is sudden stoppage result in a pressure wave which moves upstream with velocity of sound in the medium which is reflected back and fourth until dissipated by friction and im-perfect elasticity. Water hammer is caused due to sudden stoppage of water flow in a pipe .

Rise of pressure (p) due to sudden stopping of flow in a pipe is -

P = v / √ g/w ( 1/k +D/tE )

V = velocity of flow in pipe of diameter D , 

thikness t and coefficient of elasticity E

K = coefficient of bulk modulus of fluid, and

w = specific weight of fluid .

Hydraulic coefficient

Orifice -: orifice is a smaller opening of the side or at bottom of a tank . Mouthpiece is a short length of pipe is 2-3 times of it's dia-meter in length fitted in a tank of vessel con- taining the fluid. 

The various types of hydraulic coefficient 

1. Coefficient of velocity -: The ratio of the velocity of the jet at vena-contracta to the theoretical velocity is known as coefficient of velocity. In the terms of coordinates ( a,b) for vena-contracta, Cv = a / √4bH .

H = Height of fluid in the tank.

The average value of  coefficient of velocity is 0.97.

2. Coefficient of discharge -: coefficient of discharge iss the ratio of the actual discharge through or orifice to theoretical discharge. 

0.62 is the average value of the coefficient of discharge. 

3. Coefficient of resistance -: The coefficient of resistance is treated equal to zero for all the practical purpose. The ratio of the loss of head in the orifice to the head of water available at the orifice exist is known as the coefficient of resistance. 

4. Coefficient of contraction-:Coefficient of contraction is the ratio of the area of the jet at vena-contracta to the area of the orifice opening. The average value of the coefficient of contraction is 0.64 .

Fluid mechanics MCQ-03

Q.1 The flow whose stream line may be re - presented by straight lines is called which type of flow ?

A. Uni directional flow

B. Two dimensional flow 

C. One dimensional flow

D. One directional flow 

Ans-: C

Q.2 Reynold's number for laminar flow is __.

A. 2000

B. More than 2000

C. Less than 2000

D. 1000

Ans-: C

Q.3 Reynold's number for turbulent flow is ______.

A. More than 10000

B. More than 4000

C. Less than 4000

D. 4000 

Ans-: B

Q.4 The transition from laminar to turbulent flow in a pipe depends on velocity , pipe diameter and kinematic viscosity of the fluid is known as which law?

A. Buoyancy law

B. Reynolds law

C. Avegadro law

D. Bernoulli law

Ans-: B

Q.5 The flow of liquid whoes stream line may be represented by the curve is called __.

A. Two dimensional flow 

B. Three dimensional flow

C. Two directional flow 

D. None of these 

Ans-: B

Q.6 laminar flow is also known as ____.

A. Uniform flow 

B. Steady flow 

C. Stream line flow 

D. Simple flow 

Ans-: C

Q.7 In laminar flow ____.

A. Liquid particles cross each other 

B. Liquid particles do not cross each other 

C. Liquid particles have constant velocity 

D. All of the above 

Ans-: B

Q.8 Dimensions of surface tension are ____.

A. M^1 L^0 T ^-2

B. M^2 L^1 T ^-1

C. M^1 L ^2 T^-2

D. M^-1 L ^2 T^2

Ans -: A

Q.9 Due to the property of _____ falling drop of water become sphere .

A. Adhesion 

B. Surface tension 

C. Cohesion

D. Temperature 

Ans-: B

Q.10 _____ is used in manometers because it provide longer column due to low density.

A. Methanol 

B. Mercury 

C. Water

D. Alcohol 

Ans -: D

Q.11 stoke is the unit of _____.

A. Viscosity 

B. Kinematic viscosity 

C. Specific viscosity 

D. Velocity if fluid 

Ans-: B

Q.12 The buoyancy force is depend on the __.

A. Viscosity of fluid 

B. Mass of liquid displaced 

C. Force of body

D. Pressure of water 

Ans-: B

Q.13 The speed of sound in a ideal gas varies directly as its ____.

A. Temperature 

B. Absolute temperature  

C. Pressure 

D. Density of gas

Ans-: B

Q.14 what is the average value of coefficient of the discharge?

A. 0.52

B. 0.62

C. 0.72

D. 0.27

Ans-: B

Q.15 whatis the average value of coefficient of the velocity?

A. 0.79

B. 0.97

C. 0.59

D. 0.12

Ans-: B

Different types of flow

The path followed by a liquid particle in motion, is called " path line ".

According to equation of continuity og liquid flows or fundamental equation of liquid flow,if an incompressible liquid flow con- tinuously through a pipe or channel, the discharge remains the same irrespective of the cross - section.

Laminar flow -: The flow in which path of the individual particles of liquid do not cross each other, is called stream line flow or " laminar flow " .Reynolds number is less than 2000 for laminar flow. 

Turbulent flow -: In this type of flow path of the individual particles cross each other and particles do not have a definite paths called turbulent flow. For turbulent flow Reynolds number is more than 4000.

Uniform flow -: In uniform flow the ve - locities of liquid particles at the all section of the pipe , channel are equal. This generally refers to flows in channel. 

Non-uniform flow -: The flow in which ve - locities,of liquid particles at all section of the pipe or channel are not equal is called " non- uniform flow " .

Steady flow -: In this type of flow, the quantity of liquid flowing per second is constant is called stream line flow. 

Unsteady flow-: The flow in which the quantity of liquid flowing per second is not constant is called " unsteady flow  ".

Stream line-: The imaginary line, tangent to which , at any point indicates the direction of the motion at the point , is called " stream line " .

Streak and potential line -: The line in which the instantaneous positions of all fluid particles which have passed through a given point , is called streak line .

And the line joining the points of equal potential on adjacent flow lines, is called the  " potential line or equipotential line " .

Fluid mechanics MCQ-02

Q.1  At 0° C surface tension of water is ___.

A. 47.16 dyn/cm

B. 71.31 dyn/cm 

C. 74.16dyn/cm

D. 60.71dyn/cm

Ans-: C

Q.2 The force per unit area exerted by water on the sides and bottom of it's container is called ?

A. Total pressure 

B. Water pressure 

C. Water force 

D. None of these 

Ans-: B

Q.3 In a closed system, water vaporises rapidly in regions where the pressure drops below the vapour pressure. This phe -nomenon is known as _______.

A. Cavitation 

B. Conservation

C. Vaporization 

D. All of the above 

Ans-: A

Q.4 which of the following is dimensionless?

A. Specific speed 

B. Specific volume 

C. Specific gravity 

D. Specific weight 

Ans-: C

Q.5 For water at 0° C value of mass density in kg sec^2 / m^4 is ____.

A. 1

B. 10

C. 100

D. 1000

Ans-: C

Q.6 Absolute pressure is equal to atmospheric pressure and ____ pressure. 

A. Gauge pressure 

B. Surrounding pressure 

C. Vacuum pressure 

D. None of these 

Ans-: A

Q.7 in which flow ,the velocitiesof liquid particles at all section of the pipe and channel are equal?

A. Constant flow

B. Uniform flow

C. Linear flow

D. Nin- uniform flow

Ans-: B

Q.8 The instantaneous position of all liquid particles which have passed through a given point is called ______.

A. Streak line

B. Non - streak line

C. Straight line 

D. None of these 

Ans-: A

Q.9 which device is used for measuring the rate of flow of liquid through a small channel. 

A. Notch

B. Venturimeter

C. Thermometer 

D. All of the above 

Ans-: A

Q.10 The flow in which the quantity of liquid flowing per second is constant is called ____.

A. Turbulent flow

B. Steady flow

C. Uniform flow 

D. Laminar flow 

Ans-: B

Q.11 In which law path of individual particles of liquid do not cross the each other is called ?

A. Stream line flow

B. Laminar flow 

C. Un-steady flow

D. A+B

Ans-: D

Q.12 The density of water is 1000 kg/m^3 at which temperature?

A. 0° C 

B. 4 ° C

C. 0 ° K

D. 237.16 K 

Ans-: B

Q.13 What us the unit of surface tension?

A. Newton / m^2

B. Newton/ m

C. Newton/ m^2

D. Newton m

Ans-: B

Q.14 For which flow , general energy equation holds ?

A. Steady flow 

B. Turbulent flow 

C. Non- uniform flow 

D. All of the above 

Ans-: C

Q.15 pitot tube us used for measurement of _______.

A. Pressure 

B. Temperature 

C. Velocity 

D. Viscosity 

Ans-: C

Fluid mechanics basic

Fluid  -: A fluid is a substance that is capable of flowing , conform to shape of containing vessel. It also deforms continuously when it issubjected to even a smallest shear stress.

An ideal fluid is frictionless and also it is incompressible .

Viscosity-:It is the property of fluid by virtue of which it offers resistance to shear. Viscosity is caused by cohesive for between molecules of liquid and by collision between molecules of gas .Viscosity is practically independent of pressure and depend upon temperature only .

Unit of viscosity " poise " or 1 gm /cm/ sec.

( 1 poise = 0.1 Ns/ m^2 )

Kinematic viscosity -: It is the ratio of dynamic or absolute viscosity and density. It's unit is stoke . Stoke is equal to 1cm^2/sec.

Newton's law of viscosity -: newton's law of viscosity state that shear stress  ( between  adjacent layer of fluid) is directly proportional to velocity gradient. 

Shear stress = 𝝁 du / dx

( 𝝁 = coefficient of viscosity Pa sec or Ns/ m^2)

du/dx is known as velocity gradient or rate of shear strain and it is zero for fluids at rest.                                                                                          Fluid following newton's law of the viscosity is known as Newtonian fluids and other non - Newtonian fluids. An ideal fluid offers no resistance to flow but real fluid does.

( viscosity is zero for ideal fluid but not for real fluid. )

Surface tension -:                                                                   Liquid molecules are attracted to each other by equal forces in all directions. On the surface they are subjected to an inward attraction which us not balanced by the outward attraction. This cause the liquid surface to seek a minimum possible area due to surface tension. 

Surface tension is also expressed as force per unit length . 

Fluid mechanics MCQ -01

Q.1 Viscosity is the property of _____.

A. Solid 

B. Liquid 

C. Gas 

D. Substance 

Ans-: B

Q.2The ratio of absolute or dynamic viscosity and the density is known as ___.

A. Viscosity ratio 

B. Kinematic Viscosity 

C. Absolute viscosity 

D. All of the above 

Ans -: B

Q.3 The law which satate that shear stress is proportional to du/ dx is called _____.

A. Newton's law

B. Fluid law

C. Avogadro's law 

D. NOT

Ans -: A

Q.4 what is expressed as force (F)  per unit length ?

A. Surface tension 

B. Force 

C. Adhesion 

D. Cohesion 

Ans-: A

Q.5 What is the meaning of capillarity of the water ?

A. The phenomenon of rising water in a tube of small diameter dipped in water.

B. The phenomenon of falling  water in a tube of small diameter dipped in water. 

C. The phenomenon of rising water in a tube of large diameter dipped in water. 

D. None of these 

Ans -: A

Q.6 The intensity of pressure at any point in a fluid at rest, is the same in all direction.

A. Pascal law

B. Charles law

C. Newton law

D. Boyle's law 

Ans -: A

Q.7 Gauge pressure is measured with re - ference to ______.

A. Atmospheric pressure 

B. Absolute pressure 

C. At zero temperature 

D. None of these 

Ans-: A

Q.8 Local atmospheric pressure is measured by which instrument ?

A. Thermometer 

B. Mercury barometer 

C. Aneroid barometer 

D. B + C 

Ans -: D

Q.9 Density of water is maximum at ____.

A. 0 ° C

B. 4 ° C

C. 0 ° K

D. 100 ° C

Ans-: B

Q.10 Property of fluid by which it's own molecular are attracted is called ____.

A. Viscosity 

B. Adhesion 

C. Cohesion 

D. Surface tension 

Ans-: C

Q.11 Fluid is a substance which offers no re - sistance to change of ___.

A. Shape 

B. Pressure 

C. Temperature 

D. Volume 

Ans -: A

Q.12 In-viscous and incompressible fluids is known as ______.

A. Real fluid 

B. Ideal fluid 

C. Viscous fluid 

D. Pure fluid 

Ans-: B

Q.13 Liquid are not affected by change in pressure and temperature.

A. Yes 

B. No

C. At 0° C

D. None of these 

Ans -: B

Q.14 Units of mass density is ?

A. Kg sec / m^4 

B. Kg / m^3

C. Kg / km

D. Kg sec ^2 / m ^4

Ans -: D

Q.15 why , mercury  does not wet the glass?

A. Because of viscosity 

B. Because of cohesion

C. Because of adhesion

D. Because of surface tension 

Ans-: B

Statement of various law's

1. First law of thermodynamics 

Statement -: For a closed system undergoing a cycle net heat transfer (∑Q) is always equal to the net work transfer (∑w).

[ ∑Q = ∑w ] ( valid for cycle)

First law of thermodynamics is nothing but conservation of energy .

dQ = dE + dW     dQ = heat suply

dE = internal energy  dW = Work done

 This is the first law of thermodynamics for closed system undergoing a process .

( reversible and irreversible)

dW = P . dV 

For reversible process - dQ = dE + P.dV

Statement- when kinatic energy and poten tial energy are neglected. 

Second law of thermodynamics-:First law of thermodynamics says that energy is constant. It does not give any direction for a perticular process .

Second law of thermodynamics given diection of process, the concept of entropy  , hence this also known as directional law .

Calcius statement -: It is impossible to transfer heat from lower temperature to higher temperature without any external input .

Concept of heat engine

Heat engine -: Heat engine is a device which converts part of heat into work , and also re-jected some amount of heat to the surroun-ding source and sink .

Source ----- E ------ sink 

(Q1=Qs)       |        ( Q2= Qr)

                  Work

Q1 = Q2 + w 

W = Q1 - Q2  ------ eq. 1

Efficiency = w / Q1 

Eff.  = Q1 - Q2 / Q1

Eff.  = 1 - ( Q2 / Q1 )

Eff.  = 1 - ( Qr / Qs )

* Relationship between coefficient of         heat pump and cop of refrigeration-:

Working between some temperature limits-

Cop ( heat pump)   =  Q1 / ( Q1 - Q2) 

Cop ( refrigeration)   Q2 / ( Q1 - Q2 )

=     Q1        ×    Q1 - Q2  

   Q1- Q2               Q2

Cop ( H.P.)     =  Q1 / Q2

Cop ( R.f.)

Cop ( H.P )  -  Cop ( R.f.) = 1

      Q1      -         Q2      = 1

 Q1- Q2        Q1 - Q2 

Q1  -  Q2     = 1 .

Q1  -  Q1

Thermodynamics defination

Thermodynamics equilibrium -:

A system said to be exist in a state of thermo - dynamics equilibrium, when no change in microscopic properties .

Microscopic properties-:

1. Mechanical -: Equality of force.

2. Physical -: Equilibrium of temperature. 

3. Chemical -: Equilibrium of chemical com - position .

 Pure substance -: A substance is said to be     pure substance, if it is homogeneous chemical composition and homogeneous is chemical .

 Steam         H2 + o2        H2 + o

-----------        -----------        -----------

Water             H2o            water

( pure)        ( not pure )   ( not pure)

Adiabatic process -: A process is said to be adiabatic if there is no heat transfer from the system or to the system. 

Generalise equation for adiabatic process--

 PV^r = c ( r = adiabatic index)

 W = P1.V1 - P2.V2 / r - 1

Polytropic  process-: In adiabatic process there is no hear transfer only work transfer,

But in polytropic process there is heat trans-fer as well as worktransfer. 

Generalise equation for polytropic process--

   PV ^ n = c   ( n = polytropic index ) 

    r = Cp / Cv
   Cp - Cv = R                                                               W ( polytropic ) = P1.V1 - P2.V2/ n-1
   (r > 1 ,   n > 1 ,   r > n ).

Wet region-: It is the region where vapour and liquid exest in equilibrium. 

In this case- T ( actual) = T ( saturated)

Dry ice -: Dry ice , that is called solid co2 , when exposed to 1 atmospheric pressure , it 

Vaporized directly without absorbing latent heat of sublimation.                                                                             The slop of sublimation and vaporization is positive. Also slop of fusion is positive or all the case except water.

Triple point  -:  The triple point is a point   where all three phases co- exist. the triple   point of water is 4.58 mm(p) of Hg and tem-

 Perature is 0.01 ° C or 237.16 K.

Perceptual motion machine -1 and Heat transfer

Perceptual motion machine-1 -: perceptual motion machine, which devo-loped works continuously without absorbing some other form of energy, if sach a machine is develop -  ed it would first law of thermo-dynamics. 

 Q = 0 --- PMM -1 --- w

PMM -1 is impossible. 

dv = m.Cv.dT ,      

dH = m.Cp.dT

Here  U = f ( t )

Heat transfer -: 

Heat transfer in various non - flow process--

1. Constant volume process -:

Heat transfer in a constant volume process for a closed system is equal to change in thermal energy .

dQ = du + P. dv

When , v = Constant,  dv = 0 dw = 0

Then dQ = dv

2.  Constant pressure process-: 

Heat transfer for a constant pressure process is equal to change in Enthalpy. 

dQ = du + P. dv

When , P = Constant 

dQ = du + P ( dv )   , dQ = d ( u + Pv )

dQ = dH

3. Isothermal process-: 

When an ideal gas undergoes isothermal process , heat transfer is equal to work .

dQ = du + P.dv

When , T = Constant  if  u = f ( t ) du = 0

dQ = dw .

Thermodynamics MCQ - 05

Q.1 At very high pressure , an ideal gas as compared to a real gas occupies ______.

A. Same volume 

B. More volume 

C. Less volume 

D. None of these 

Ans-: B

Q.2 Superheated vapour behaves like ___.

A. As steam 

B. Exactly as gas 

C. Water

D. Approximately as a gas

Ans-: D

Q.3 Which law states that , the specific heat of a gas remain constant at all temperature and pressure?

A. Regnault's law

B. Boyle's law 

C. Joules law 

D. Avogadro's law

Ans-: A

Q.4 Thermocouple based on the ____.

A. Temperature of two bodies

B. Atmospheric pressure 

C. See - back effect 

D. Atmospheric temperature 

Ans-: C

Q.5 Air contains following parts of the oxygen. ( on the weight basis )

A. 24 

B. 23

C. 30

D. 73

Ans-: B

Q.6 In thermodynamics cordinates properties of substance like , pressure, temperature and density are ______.

A. Real function 

B. Point function

C. Cyclic function 

D. Thermodynamics function 

Ans-: B

Q.7 which of the following is not a path function?

A. Heat

B. Work 

C. Kinatic energy 

D. Thermal conductivity 

Ans-: D

Q.8 In a cycle heat us rejected at____.

A. Constant pressure 

B. Constant temperature 

C. Constant volume

D. All of the above 

Ans-: A

Q.9  Flow of steam through a nozzle is ___.

A. Constant flow

B. Adiabatic flow

C. Isothermal flow

D. Constant pressure flow

Ans-: B

Q.10 The ratio of number of moles of a gas to total number of moles is known as _____.

A. Ideal gas 

B. Mole fraction 

C. Enthalpy 

D. Molecular ratio

Ans-: B

Q.11 Real gas follows,  PV = nRT ?

A. Yes 

B. No

C. At constant temperature 

D. At constant pressure 

Ans-: No 

Q.12 The region where vapour and liquid exest in equilibrium is called ___.

A. Hot region 

B. Wet region

C. Cold region

D. None of these 

Ans-: B

Q.13 Solid "Co2" is also known as _____.

A. Dry solid 

B. Dry ice 

C. Dry Co2

D. Dry gas 

Ans-: B

Q.14 The triple point is a point , where ___.

A. Two phases co - exist 

B. Three phases co - exist 

C. No phase co - exist 

D. None of these 

Ans -: B

Q.15 Triple point of water is ____.

A. 4.58 mm(p) of Hg

B. 0

C. 45.8 mm (p) of Hg

D. 1 

Ans -: A

Physical meaning of entropy and Enthalpy

Entropy is a measure of molecular dis - oderness or randomness, greater is the disorderness lesser the efficiency.                    " Entropy change of univers "

  ds >or = dQ/ T

  ds (universe) > or = 0 

( universe is a isolated system)

ds ( system) + ds ( surrounding) > or = 0

Entropy of the system can increase or decrease or it can remain constant. Similarly the entropy of surrounding can increase or decrease or it can remain constant but " the overall change in Entropy of univers can never decrease.

Q. What is source and sink?

Ans-: source-: source is a reservoir, which supplies thermal energy without undergoing any temperature change .

Sink -: It is a reservoir which absorb thermal energy without undergoing any temperature change. 

Enthalpy -: In thermodynamics the term " u + Pv " is taken as Enthalpy. 

H = u + Pv

It is an extensive property and generally express in " KJ".

Specific Enthalpy  H/m = h = KJ/Kg

Zeroth law and thermometer

Zeroth law of thermodynamics -:

Zeroth law of thermodynamics is that , when a body "A" is in thermal equilibrium with body "B" and the body "B" is in thermal equilibrium with body "C" , then automatically body "A" will be in thermal equilibrium with body " C".

       The concept of the thermometer  is based on the " zeroth law of thermodynamics "

Thermometer -: Thermometer is a device or a measuring instrument which is used to measure temperature ( how hot or cold some- thing is ).

Types of thermometer--

1. Resistance thermometer 

2. Thermo couple -: It is based on the see - back effect .

3. Constant volume gas thermometer-:

    It is works on the pressure change .

4. Constant pressure gas thermometer-:

    It is works on the change in volume. 

Throttling process

Throttling process -: when steam is pass from a respectable path such as partially opened valve , it's pressure reduces but the entropy of the steam remian constant this prcess is known as throttling process.

                In this process there is no change in Enthalpy from state one to state two , h1 = h2

,no work is done and process is adiabatic ,

 Q= 0.

Concept of entropy

First law of thermodynamics says that energy is constant, it does not give any direction for a particular process. 

           But the second law of thermodynamics gives direction of processe  the concept of entropy hence second law of thermdynamics also known as "directional law " .

Thermodynamics MCQ- 04

Q.1 Real gas follows which relation ?

A. PV= nRT

B. PV×compressbility factor = nRT

C. (PV)^n = RT

D. PV^n = C

Ans-: B

Q.2 1 bar is =_______.

A. 1.0197 kgf/cm^2 or 750.06 mm Hg

B. 735.6 mm Hg

C. 100 mm Hg 

D. 1.033 kgf/cm^2 or 760 mm Hg

Ans-: A

Q.3 According to james law ____.

A. Q = W/J

B. W = Q/J

C.  J = Q/W

D. W = J/Q 

Ans-: D 

Q.4 At constant pressure, when a liquid boils , the following parameter increases?

A. Enthalpy 

B. Entropy 

C. Temperature 

D. Kinetic energy 

Ans-: B

Q.5 For which process work done is zero ?

A. Constant volume 

B. Free expansion 

C. Throttling 

D. All of the above 

Ans-: D

Q.6 No liquid exists as liquid at ____.

A. Zero temperature 

B. Zero pressure 

C. Vacuum 

D. In space 

Ans-: B

Q.7 Temperature of a gas produced due to ____.

A. It's heating value 

B. Kinetic energy of molecules 

C. Surface tension of molecules 

D. Enthalpy 

Ans-: A

Q.8 According to Gay- lussac law, for a perfect gas, the absolute pressure of given mass varies directly as ___.

A. Temperature 

B. Pressure 

C. Absolute temp. , if volume is kept constant

D. All of the above 

Ans-: C

Q.9 The smallest quantity ehich take part in a chemical reaction is known as _.

A. Molecule

B. Atom

C. Carbon

D. None of these

Ans-: A

Q.10 The ratio if brake or actual work done to the indicated work done is called ?

A. Relative efficiency 

B. Mechanical efficiency 

C. Total efficiency 

D. Thermal efficiency 

Ans-: B

Q.11 For complete combustion an axcess quantity of air required in order to permit intimate mixing of fuel with oxygen is known as ___.

A. Excess fuel 

B. Excess air 

C. Oxygen 

D. All of the above 

Ans-: B

Q.12 According to Boyle's law ___.

A. PV = 0

B. PV = Constant 

C. PV = 1

D. PV = 1/2

Ans -: B

Q.13 According to first law of thermodynamics total energy of univers remain _______.

A. Constant 

B. Increases

C. Decreases

D. Zero 

Ans-: A

Q.14 In isolated system __.

A. Matter can not interchange 

B. Energy can not interchange 

C. Matter and energy can interchange 

D. A+B

Ans-: D

Q.15 In open system ___.

A. Energy can interchange 

B. Matter can  interchange 

C. A+B 

D. Energy and matter can not interchange 

Ans-: C

Heat

Heat-: Heat is a form of energy that can be move between two things when one of them is hotter then the other.

         In other words, the amount of thermal energy in a system is also known as heat.

Q. What is sensible heat ?

Ans-: The heat required to raise the temperature of 1kg of liquid from 0°C to the boilling point. Sensible heat is denoted by"h".

                   Sensible heat is related to changes temperature of gas or object with no changes in phase .

Thermodynamics MCQ-03

Q.1 The zeroth law of thermodynamics deals with ______.

A. Conversion of heat and mass

B. Reversibility of a process

C. Introduction of concept of entropy 

D. Transitivity of thermal equilibrium 

Ans-: D

Q.2 Which of the following defined specific fuel consumption?

A. Fuel consumption per hour 

B. Fuel consumption per km

C. Fuel consumption per hr per BPH

D. Fuel consumption per BPH

Ans-: C

Q.3 Combustion of gases fuels deals with _____.

A. Dalton's law

B. Avogadro's hypothesis 

C. Krichhoff's law

D. Boyle's law

Ans-: B

Q.4 A substance above critical temperature exists as_____.

A. Solid

B. Liguid

C. Vapour 

D. Supersaturated fluid

Ans-: D

Q.5 When a vapour condenses into a liquid then ____.

A. It evolves heat

B. It absorbs heat

C. No change in heat

D. Its temperature rises

Ans-: A

Q.6 On which cycle constant pressure gas cycle work ____. 

A. Otto cycle 

B. Brayton cycle

C. Rankine cycle 

D. Dual cycle 

Ans-: B

Q.7 Entropy is defined by which law?

A. Gas law 

B. First law of thermodynamics 

C. Second law of thermodynamics 

D. Zeroth law of thermodynamics 

Ans-: C

Q.8 Water is a______.

A. Substance 

B. Liquid 

C. Compound 

D. mixture 

Ans -: C

Q.9 When the cut off is _______ efficiency of diesel cycle is maximum.

A. Increased

B. Zero

C. Decreased 

D. Maximum 

Ans-: B

Q.10 Total heat of a substance is also known as ____. 

A. Entropy 

B. Calorific value 

C. Enthalpy

D. Specific heat of substance 

Ans-: C

Q.11 Heat is rejected,  In a cycle ____.

A. At constant pressures 

B. At constant volume 

C. At constant temperature 

D. At constant Enthalpy 

Ans-: A

Q.12 In the barometric reading sudden fall is the sign off approaching ____.

A. Cold wave 

B. Rain

C. Strom

D. Fine weather 

Ans-: C

Q.13 Unit of universal gas constant is ___.

A. Nm/kg mole °k

B. Nm/ kg

C. Nm/kg °k 

D. N/m/ °k 

Ans-: A

Q.14 How many value of specific heat solid and liquid have?

A. 1

B. 2

C. 3

D. 5

Ans-: 1

Q.15 In closed system ____.

A. No interchange of matter 

B. Only energy cross the boundaries 

C. Boundary can move or change position 

D. All of these 

Ans-: D 

Calorific value of fuel

Calorific value of fuel -: The combustion of fuel is accompanied by a large amount of evolution of heat. In kcal , the number of heat units evolved by the complete combustion of fuel is called the calorific value of fuel .

         

Calorific value can be determined by boy's gas calorimeter or by bomb calorimeter.

Calorific value of fuel measured in two types- 

1. Higher calorific value ( H.C.V.)

2. Lower calorific value  (L.C.V.)

1. Higher calorific value -: The amount of heat liberated by tge unit quantity of fuel i.e., 1 kg , when the products of combustion are cooled to 15° C is called higher calorific value or gross calorific value of fuel. 

2. Lower calorific value -: It is defined as ,when heat taken away by the water due to surface moisture and combustion is subtract from higher calorific value is called lower calorific value. 

 L.C.V. = H.C.V. - Heat taken by water due to surface moisture and combustion 

L.C.V. = H.C.V. - Weight of water × Latent heat

Thermodynamics MCQ-02

Q.1 A perfect gas follows which law?

A. Joules law

B. Boyle's law

C. Charles law

D. Gay -lussac law

E.  All off the above

Ans-: E

Q.2 S.I. unit of mass is ________.

A. Tonne

B. Gram

C. Kg

D. Newton

Ans-: B

Q.3 which is general gas equation?

A. PV^n = C

B. PV= nRT

C. PV= mRT

D. Cp- Cv = R/J

Ans-: C

Q.4 S.I. unit of pressure ______.

A. Bars 

B. Kg/cm^2

C. Pascal 

D. Mm of water column 

Ans-: C

Q.5 How many law's fully determined behaviour of gases? 

A. 1 law

B. 2 law

C. 5 law

D. 4 law

Ans-: D

Q.6 Ice and water form a mixture of_____.

A. Open system 

B. Closed system 

C. Heterogeneous system 

D. Isolated system 

Ans-: C

Q.7  1 N/m^2 is equal to _____.

A. 5 watt 

B. 3 watt

C. 2 watt

D. 1 watt

Ans-: D

Q.8 The unit of entropy is _____.

A. Nm/kg sec

B. J/°k

C. J/kg °k

D. J/kg

Ans-: C

Q.9 which of the following is not the property of the system?

A. Density

B. Pressure 

C. Heat

D. Temperature 

Ans-: C

Q.10 In kg one calorie us equal to _____.

A.  .0427

B.  4.27

C.  427

D.  42.7

Ans-: A

Q.11 Who developed first law of thermodynamics?

A. Kelvin

B. Joule

C. Carnot 

D. Charles

Ans-: B

Q.12 Charles law is ___. ( P is constant )

A. V=T=Constant

B. V×T×Constant 

C. V/T = Constant

D. None of these

Ans -: C

Q.13 Measurement of temperature is based on ____.

A.  Thermodynamics properties 

B.  Zeroth law of thermodynamics 

C.  First law of thermodynamics 

D.  Joules law 

Ans -: B

Q.14 At  0° C value of entropy taken as___.

A.  1

B. -1

C.  Zero 

D.  2

Ans -: C

Q.15 Thermal power plants work on which cycle?

A. Rankine cycle 

B. Otto cycle 

C. Joules cycle 

D. Carnot cycle 

Ans -: A

Thermodynamics MCQ-01

Q.1 The unit of temperature in S.I. unit _____.

A. Kelvin     

B. Celsius

C. Centigrade 

D. All of the above 

Ans.: A

Q.2 The unit of energy _____.

A. Joule/sec

B. Watt

C. Joule

D. Erg

Ans.: C 

Q.3 Erg is unit of ______.

A. Energy

B. Electric power 

C. Heat

D. Work

Ans.: B

Q.4 How many fundamental units ___.

A. 5

B. 7

C. 6

D. 9

Ans.: B

Q.5 what is the S.I. unit of power?

A. Erg

B. Newton

C. Joule

D. Watt

Ans.: D

Q.6 what is the S.I. unit of time?

A. Hour

B. Minute

C. Second

D. Day

Ans.: C

Q.7 Length is measured in ______.

A. Meter/sec

B. Km/hour

C. Meter 

D. All of the above

Ans.: C

Q.8 Internal energy of a substance depend on _______.

A. Volume 

B. Entropy 

C. Temperature 

D. Pressure 

Ans.: C

Q.9 First law of thermodynamics define ___.

A. Conservation of mass.

B. Conservation of energy.

C. Conservation of heat.

D. None of the above. 

Ans.: B

Q.10 In S.I. unit 1 bar is equal to  ____. 

A. 1 kN/m^2

B. 1×10^5 N/m^2

C. 1×10^4 N/m^2

D. 1×10^6 N/m^2

Ans.: B

Q.11 What is the value of Barometric pressure?

A. 100 mm Hg

B. 1 mm Hg 

C. 735.6 mm Hg

D. 760 mm Hg

Ans.: D

Q.12 In which cycle air refrigerators work? 

A. Otto cycle 

B. Carnot cycle 

C. Reversed joule cycle

D. Diesel cycle

Ans.: C 

Q.13  1 KWH of energy is equal to _____.

A. 3600 joule 

B. 3600 kJ 

C. 100 J

D. 36000 KJ

Ans.: B 

Q.14  which of the following measured in calorie ? 

A. Work

B. Entropy

C. Specific heat

D. Quantity of heat 

Ans.: D

Q.15 What is the unit of universal gas constant? 

A. Watts/°k

B. Erg/°k 

C. Erg cm/° k

D. None of the above 

Ans.: D

Definitions

Macroscopic approach :-               macroscopic deals with certain quantity of matter  and its behaviour. 

Microscopic approach  :-                microscopic approach concerned with molecular and atomic behaviour of energy and matter.

Thermodynamic system :--Thethermodynamic system is a fixed quantity of matter, around which we can draw a boundary. The boundary may be moveable or fixed. 

There are 3 types of system -- 

1.  Closed system :-                                             In this system there is no interchange of matter between surrounding and system . In this system only energy can cross the boundaries and the boundary also can move or change its position .

2.Open system :-                                                     In this type of thermodynamic system matter and energy both can interchange from the system.

3. Isolated  system :- 

   In this type of thermodynamic system both matter and energy no one can cross the boundaries. Isolated system not influenced by the surrounding .