Review of Mechanical Engineering

 

1. What is the diference between isotropic and anisotropic materials ?

Ans: I a material exhibits same mechanical properties regardless o loading direction, directio n, it is isotropic, e.g., homogeneous cast materials. Materials lacing this propert! are anisotropic.   ". What are orthotropic materials ? Ans: It is a special class o anisotropic materials which can be described b! gi#ing their prop$erties in three perpendicular directions e.g. wood% composites.   &. What is #iew actor ? Ans: 'iew actor is dependent upon geometr! o the two suraces exchanging radiation.   (. What properties need to be considered or applications calling or ollowing re$)uirements : *i+ rigidit! *ii+ strength or no plastic deormation under static load *iii+ strength to withstand o#erload without racture. *i#+ wear resistance *#+ reliabilit! and saet!. Ans: *i+ igidit!-lastic modulus and !ield strength *ii+ /trength *or no plastic deormation under static loading+-!ield point *iii+ /trength *o#erload+-0oughness and impact resistance *i#+ Wear resistance-ardness *#+ eliabilit! and saet!-ndurance limit and !ield point.   2. xplain the efects o allo!ing chromium and nicel in stainless steel. Ans: Addition o nicel and chromium increases the tensile strength and increase in resistance to corrosion taes place.   3. Mention two t!pes o dislocations. Ans: 4islocation reers reers to a brea in the continuit! o the lattice. In edge dislocation, one plane o atoms gets s)uee5ed out. In screw dislocation dislocation the lattice atoms mo#e om their regular ideal positions.   6. What are the principal constituents o brass? Ans: 7rincipal constituents o brass are copper and 5inc.   8. What is 9urie point ? Ans: 9urie point is the temperature at which erromagnetic materials can no longer be magnetised b! outside orces.   . /peci;c strength o materials is #er! high when the! are in ;bre si5e but lower when the! are in bar orm Wh! ?

 

Ans: 9r!stal structure has ordered, repeating arrangement o atoms. <ibres are liable to maintain this and thus ha#e high speci;c strength. As si5e increases, the condition o ordered and repeating arrangements can=t be guaranteed because o se#eral t!pes o deects and dislocations and thus the speci;c strength gets lower.   1>. What is the percentage o carbon in cast iron ? Ans: ".2.   11. Which element is added in steel to increase resistance to corrosion ? Ans: 9hromium.   1". Whether indi#idual components in composite materials retain their characteristics characteris tics or not? Ans: !es.   1&. An elastomer elastomer is a pol!mer when its percentage percentage elongation rate is ? Ans: @reater than 1>>.   1(. I percentage elongation o a material is more more than ">>, it is classed as ? Ans: ubber.   12. Wh! is it that the maximum #alue which the residual stress can reach is the elastic limit o the material ? Ans: A stress in excess o elastic limit, with no external orce to oppose it, will relie#e itsel b! plastic deormation until it reaches the #alue o the !ield stress.   13. Wh! atigue strength decreases as si5e o a part increases be!ond around 1> mm? Ans: 7erection o material conditions is possible at lower si5es and as si5e increases, it is not possible to attain uniorm structure o the material.   16. 4istinguish between creep and atigue. Ans: 9reep is low and progressi#e deormation o a material with time under a constant stress at high temperature applications. <atigue is the reduced tendenc! o  material to ofer resistance to applied stress under repeated or uctuating loading condition.   18. While normal carburising and nitriding surace treatments increase atigue strength, excessi#e treatment ma! decrease the atigue strength. Wh! ? .Ans: Bormal carburisingCnitriding treatments increase #olume due to phase transormation at /urace and introduce residual compressi#e surace stress and thus increase the atigue strength. D! excessi#e treatment the high compressi#e stresses are and introduced but these are balanced b! high in$ternal stresses e)ual #alue the subsurace atigue cracs ma! de#elop in thetensile regions o higho

 

tensile stress and lead to earl! atigue ailure.   1. Eist at least two actors that promote transition rom ductile to brittle racture. Ans: Manner o loading, and the rate o loading promote transition rom ductile to brittle rac$ture. A machine member ma! ha#e ductile ailure under static loading but ma! ail in brittle ashion when the load is uctuating. /imilarl! a material ma! e#idence ductile ailure under tensile loading at ordinar! testing speed but i load is applied at a high #elocit! then ailure ma! be brittle.   ">. Whic Which h theories theories o ailur ailure e are are used or *a+ *a+ ductil ductile e material materials, s, and and * brittle brittle materials ? Ans: <or ductile materials, theories o ailure used are maximum shear stress theor!, and maximum energ! o distortion theor!% while or brittle materials, theor! o maximum principal stress, and maximum strain are used.   "1. What does thermal difusi#it! o metals signi!. Ans: 0hermal difusi#it! is associated with the speed o propagation o heat into solids during changes in temperature with time.   "". <or conduction o heat, the instantaneous rate o heat ow is product o three actors. What are these ? Ans: *i+ Area o the section o the heat ow path, perpendicular to the direction o heat ow. *ii+ temperature gradient, i.e. change o temperature w.r.t. length o path. *ii+ 0hermal conducti#it! o material.   "&. ow con#ecti#e heat transer is efected and on what actors it depends ? Ans: 9on#ecti#e heat transer is efected between a solid and uid b! a combination o molecular conduction within the uid in combination with energ! transport resulting resultin g rom the motion o uid particles. It depends on boundar! la!er con;guration, uid properties and temperature diference.   "(. Which is the common element between brass and bron5e bron5e ? Ans: 9opper 9 opper..   "2. What does ollowing allo! designation indicate <@ "2> ? Ans: @re! cast iron with tensile strength o "2> M7a.   "3. ow is ceramic de;ned ? Ans: It is a solid ormed b! combination o metallic and nonFmetallic elements.   "6. @i#e one example o metal classi;ed as per structure as D99, <99, 97 and 997. Ans:

D99 *bod! centred cubic+ structure-Mol!bdenum structure-Mol! bdenum

 

<99 *ace centred cubic+ structure-Aluminium 97 *hexagonal closed paced+ structure-Ginc 997 *cubic dosed paced+ structureF9opper.   "8. What is the name o solid solution o carbon in alpha iron and delta iron ? Ans: <errite and austenite respecti#el!.   ". xplain the diference between pearlite and cementile ? Ans: 7earlite is eutectoid mixture o errite and cementile. 9ementite is chemical compound o iron and carbon.   &>. @i#e one example each o the ollowing proportion proportion o materials dimensional, ph!sical, technological and mechanical. Ans: oughness, enthalp!, toughness, and hardness respecti#el!.   &1. <or which parts the Wahl actor and Eewis orm actor used ? Ans: <or springs and gears respecti#el!.   &". ow ox!gen can be remo#ed rom steel during melting? What are ull! illed steels ? Ans: Hx!gen can be remo#ed b! adding elements such as manganese, silicon or aluminium which, because o their high anit! or ox!gen, react with it to orm nonF metallic oxides which rise into the slag. /teels which ha#e had most o their dissol#ed ox!gen remo#ed are called Jull! illed steelsJ.   &&. !drogen cannot be remo#ed easil! rom molten steel. What harm h!drogen has on propert! o steel ? Ans: xecessi#e h!drogen results in the ormation o small ;ssures oten described as hairline cracs or aes in the steel. Earge orgings in allo! steel are particularl! sensiti#e to this phenom$enon.   &(. What is allotrope ? In what orms o cubic pattern, iron exists ? Ans: /ome elements exist in more than one cr!stalline orm. ach orm is nown as JallotropeJ. Iron exists in two orms o cubic pattern, namel! bod! centered cubic *bcc+ and aceFcentered cubic *ee+.   &2. What is the diference between alpha iron, delta iron and gamma iron ? Ans: 0he bcc orm o iron exists between room temperature and 1>K9, and between 1(>>K9 and the melting point at 12&K9. 0he lower temperature orm is nown as JalphaJFiron and the higher temperature orm as JdeltaJFiron. 0he aceF centered cubic orm existing between 1>K9 and 1(>>K9 is reerred to as JgammaF ironJ.  &3. Metals, in general are o low strength and do not possess re)uired ph!sioF

 

chemical and technological properties or a de;nite purpose. Allo!s are thereore more than metals alone. 4iscuss the arrangement o atoms and structures o allo!s. Ans: Allo!s are produced b! melting or sintering two ore more metals, or metals and a nonFmetal, together. Allo!s possess t!pical properties inherent in the metallic state. 0he chemical elements that mae up an allo! are called its components. An allo! can consist o two or more components. 0he phase and structures o allo!s describe the constitution, transormations and properties o metals and allo!s. A combination o phases in a state o e)uilibrium e)uilibrium is called a s!stem. A phase is a homogeneous portion portion o a s!stem ha#ing the same composition and the same state o aggregation throughout its #olume, and separated rom the other portions o the s!stem b! interaces. <or instance, a homogeneous pure metal or allo! is a singleF phase s!stem. A state in which a li)uid allo! *or metal+ coexists with its cr!stals is a twoFphase s!stem. /tructure reers to the shape, si5e or the mutual arrangement o the corresponding phases in metals or allo!s. 0he structural components o an allo! are its indi#idual portions, each ha#ing a single structure with its characteristic eatures.   &6. What is the diference between isotropic material and homogeneous material ? Ans: In homogeneous material the composition is same throughout and in isotropic material the elastic constants are same in all directions.   &8. xplain the diference between the points o inexion and contraexure. Ans: At points o inexion in a loaded beam the bending moment is 5ero and at points o contraexure in loaded beam the bending moment changes sign rom increasing to decreasing.   &. What is the diference between proo resilience and modulus o resilience ? Ans: 7roo resilience is the maximum strain energ! that can be stored in a material without permanent deormation. deormation. Modulus o resilience is the maximum strain energ! stored stored in a material per unit #olume.   (>. What is the diference between column and strut ? Ans: Doth column and strut carr! compressi#e load. 9olumn is alwa!s #ertical but strut as member o structure could carr! axial compressi#e load in an! direction.   (1. xplain the diference diference between errite, austenite and graphite ? Ans: <errite is the solid solution o carbon and other constituents in alphaFiron. It is sot, ductile and relati#el! wea. Austenite is the solid solution o carbon and other constituents in gammaFiron. It exists in ordinar! steels at ele#ated temperatures, but it is also ound at ordinar! temperatures in some stainless steels. @raphite has a hexagonal la!er lattice. =  (". xplain the terms solid solution, eutectic, eutectoid and peritectic.

 

Ans: /olid /olution. When a homogeneous mixture o two *or more+ atomic orms exists in solid state, it is nown as solid solution. utectic. A mixture o two *or more+ phases which solidi! simultaneousl! rom the li)uid al$lo! is called an eutectic. Allo!s in which the components solidi! solidi! simultaneousl! simultaneous l! at a constant tem$perature the lowest or the gi#en s!stem, a are re called eutectic allo!s. utectoid. utectoid allo!s are the allo!s or which two solid phases which are completel! soluble become completel! insoluble on cooling beore a certain temperature temperatur e called eutectoid tem$perature. tem$perature. 7eritectic. A peritectic transormation in#ol#es a reaction between a solid and li)uid that orm a diferent and new solid phase. 0his three phase transormation occurs at a point called peritectic point.   (&. What do !ou understand b! critical points in iron, ironFcarbide diagram ? Ans: 0he temperatures at which the phase changes occur are called critical points *or tem$peratures+.   (2. Wh! 70 is preerred o#er 97M or e#aluation o proLect ? Ans: 70 is based on the approach o multiple time estimates or each acti#it!.   (3. What is the percentage o chromium chromium in 18 : ( : 1 II// ? Ans: (.   (6. What is stellite ? Ans: It is a nonFerrous cast allo! containing cobalt, chromium and tungsten.   (8. Which ra!s are produced b! cobaltF3> in industrial radiograph! ? Ans: @amma ra!s.   (. What are illed steels and what or these are used ? Ans: illed steels are deoxidised in the ladle with silicon and aluminium. Hn solidi;cation no gas e#olution occurs in these steels because the! are ree rom ox!gen.   2>. What is critical temperature in metals ? Ans: It is the temperature temperature at which the phase change occurs in metals.   21. 9ar t!res are usuall! made o ? Ans: /t!reneFbutadine rubber.   2". What is the structure o pure iron and whether it is sot or hard ? Ans: <errite and it is sot.  2&. Which elements increase the corrosion resistance o steel ?

 

Ans: 9hromium and nicel.   2(. What causes hardness in steel ? ow heat treatment alters properties o steel ? Ans: 0he shape and distribution o the carbides in the iron determines the hardness o the steel. 9arbides can be dissol#ed in austenite is the basis o the heat treatment o steel. I steel is heated abo#e the A critical temperature to dissol#e all the carbides, and then cooled, suitable cooling through the cooling range will produce the desired si5e and distribution o carbides in the errite, imparting diferent properties.   22. xplain the ormation o microstructures o pearlite, bainite and martensite in steel. Ans: I austenite containing about >.8> percent carbon is slowl! cooled through the critical temperature, errite and cementite are reLected simultaneousl!, orming alternate plates or lamellae. 0his microstructure is called pearlite. At temperatures  Lust belot the the A1, the transormation transormation rom rom austenite.to austenite.to pearlite ma! tae tae an appreciable apprecia ble time to initiate and complete, but the product will be lameller pearlite. As the transormation temperature is lowered, the time to initiate transormation shortens but the product is pearlite o increasing ;neness, and at temperatures approaching 22>K9 it cannot be resol#ed into its lamellar constituents. <urther deerease in transormation temperature causes a lengthening o the ncubation period and a change in structure o the product to a orm nown as JbainiteJ. I the temperature is lowered sucientl!, the difusion controlled nucleation and growth modes o transormation are suppressed completel! and the austenite transorms transor ms b! a difusionless process in which the cr!stal lattice efecti#el! shears to a new cr!stallographic con;guration con;guration nown as JmartensiteJ. 0his phase has a tetragonal cr!stal structure and contains carbon in supersaturated solid solution.   23. ow with allo!ing o steel it is possible to a achie#e proper properties ties which can not be achie#ed with heat treatment ? Ans: A prere)uisite the hardening o steels thato martensite be ormed on cooling, but this to can onl! be achie#ed i theisrate cooling is should great enough to suppress the ormation o pearlite or bainite and in plain carbon steels this can be achie#ed b! )uenching relati#el! relati#el! small specimens   26. What are the maLor efects o allo!ing elements? Ans: *1+ 0o alter the transormation temperatures and times *"+ 0o modi! the room temperature temperat ure and ele#ated ele#ate d temperature temperatu re strengths o gi#en structures structur es b! *a+ *a+ stifen stifening ing the the cr!sta cr!stals ls and and * introduc introducing ing comple complex x precip precipitate itates s which tend to harden the steel. *&+ 0o modi! the t!pe o oxide oxide ;lm ormed on the surace o the steel and thereb! afect its corrosion resistance.  

 

28. What is the diference between austenite stabilisers and errite stabilisers ? Ans: Austenite stabilisers ha#e the efect o extending the temperature range o#erwhich austenite is ormed. /uch elements are carbon, manganese, nicel, copper and cobalt. <errite stabilisers ha#e the efect o extending the temperature range o#er which alpha and delta errite are ormed, which conse)uentl! reduces temperature range o#er which austenite is ormed. /uch elements are silicon, chromium, mol!bdenum, tungsten, titanium and niobium.   2. What are the efects o carbon on the properties o steel. Ans: In general, an increase in carbon content produces higher ultimate strength and hardness but lowers ductilit! and toughness o steel allo!s. 9arbon also increases airFhardening tendencies and weld hardness, especiall! in the presence o  chromium. In lowFallo! steel or highFtemperature highFtemperature applications, the carbon content is usuall! restricted to a maximum o about >.12 in order to assure optimum ductilit! or welding, expanding, and bending operations. 0o minimi5e intergranular corro$sion caused b! carbide precipitation, the carbon content o austenitic *18F8 t!pe+ allo!s is limited in commercial speci;cations to a maximum o >.>8, or e#en less, i.e. >.>& in the extremel! lowFcarbon grades used in certain corrosionF resistant applications. In plain carbon steels in the normalised condition, the resistance to creep at temperatures below ((>K9 appears to increase with carbon content up to >.( carbon, at higher temperatures there is but little #ariation o creep properties with carbon content.  An increase in carbon content lessens the thermal and electrical conducti#ities o steel and increases its hardness on )uenching.   3>. What is the role o silicon as allo!ing element in steels ? Ans: /ilicon contributes greatl! to the production o sound steel because o its deoxidi5ing and degasi!ing properties. When added in amounts up to ".2, the ultimate strength o the steel is amounts increasedhigher without loss2 in ductilit!. in excess o ".2 causes brittleness, and than mae the/ilicon steel nonF malleable. esistance to oxidation and surace stabilit! o steel are increased b! the addition o  silicon. 0hese desirable efects partiall! compensate or the tendenc! o silicon to lower the creep properties o steel. /ilicon increases the electrical resisti#it! o steel and decreases h!steresis losses.   31. 4iscuss the role o manganese in allo!ing steels. Ans: Manganese is an excellent deoxidi5er and sulur neutrali5er, and impro#es the mechanical properties o steel, notabl! the ratio o !ield strength to tensile strength at normal temperatures. As an allo!ing element, manganese ser#es as an inexpensi#e means o pre#enting Jhot owe#er shortnessJ. It impro#es rolling properties, hardenabilit!, and resistance to wear. manganese increases the crac

 

sensiti#it! o weldments, particularl! with steels o higher carbon content.   3". 4e;ne bucling actor. Ans: It is the ratio o the e)ui#alent length o column to the minimum radius o g!ration.   3&. What do !ou understand b! catenar! cable ? Ans: A cable attached to the supports and carr!ing its own weight.   3(. What is coaxing ? Ans: It is the process o impro#ing atigue properties b! ;rst underFstressing and then increasing the stress in small increments.   32. What is diference between conLugate beam and continuous beam ? Ans: A conLugate beam is an imaginar! beam o same si5e as original beam and carr!ing a distributed load in accordance with the bending moment diagram. A continuous beam is one which is resting on more than two supports.   33. What is isotropic material ? Ans: It is a material ha#ing same elastic constants in all directions.   36. xplain diference between modulus o resilience and modulus o rigidit! ? Ans: Modulus o resilience is the maximum strain energ! stored in a material per unit #olume and modulus o rigidit! is the ratio o shearing stress to the shearing strain within the elastic limit.   38. What is the diference between basic hole and basic shat ? Ans: A basic hole is one whose lower de#iation is 5ero and in case o basic shat the upper de#iation is 5ero.   3. or p!ranometer used Ans:What It is used to measure is the total? hemispherical solar radiation.   6>. 4escribe transer machines in brie. Ans: It is an automatic machine in which worpiece alongwith ;xture is transerred rom one station to other automaticall! and se#eral operation on worpiece are perormed at each station.   61. What is burntFout point ? Ans: It corresponds to maximum heat ux at which transition occurs rom nucleate boiling to ;lm boiling.   6". do !ou understand ? Ans:What It is mechanical mixture b! o eutectic two or more phases which solidi! simultaneousl!

 

rom the li)uid allo!.   6". xplain the diference between gre! iron and white iron. What is mottled iron ? Ans: 0he carbon in cast iron could exist at room temperature as either iron carbide, or as graphite which is the more stable orm. Irons containing carbon as graphite are sot, easil! machinable and are called Jgre! ironsJ. Irons with carbon present as iron carbide are extremel! hard, dicult to machine and are called JwhiteJ irons. Irons with airl! e)ual proportions o graphite and iron carbide ha#e intermediate hardness and are called JmottledJ irons.   6&. 0he graphite in gre! irons exists in the orm o aes which act as stressFraisers under tensile loading and conse)uentl! gre! irons ha#e relati#el! low tensile strength and ductilit!. /till gre! iron is extensi#el! used in engineering. Wh! ? Ans: @re! iron is extensi#el! used in engineering because o ollowing characteristics. *a+ 9heapness. * Eow melting melting point point and high uidit! uidit! maing maing it suitable suitable or castings castings o intricate intricate shape. N elati#el! good erosion and corrosion resistance. *d+ igh damping capacit!, with respect to #ibration. *e+ elati#el! good mechanical mechanica l properties under compressi#e loading.   6(. Onder what condition a con#ergent di#ergent no55le re)uired ? Ans: When pressure ratio is greater than critical pressure ratio.   62. What is endurance limit and what is its #alue or steel ? Ans: ndurance limit is the maximum le#el o uctuating str stress ess which can be tolerated inde;nitel!. In most steels this stress is approximatel! 2> o the ultimate tensile strength and it is de;ned as the stress which can be endured or ten million re#ersals o stress.   63. ow the net wor to dri#e a compressor and its #olumetric ecienc! beha#e with increase in clearance #olume ? Ans: Wor remains unaltered and #olumetric ecienc! decreases.   66. What do !ou understand b! sulphur print ? Ans: /ulphides, when attached with dilute acid, e#ol#e h!drogen sulphide gas which stains bromide paper and thereore can be readil! detected in ordinar! steels and cast irons. While sulphur is not alwa!s as harmul as is sometimes supposed, a sulphur print is a read! guide to the distribution o segregated impurities in general.   68. What is the diferent between brass and bron5e ? Ans: Drass is an allo! o copper with 5inc% and bron5e is allo! o copper with tin.

 

  6. What is the efect o addition o 5inc in copper? What is the use o 6>C&> brass ? Ans: D! addition o 5inc in copper, both tensile strength and elongation increases.  0he 6>C&> brass brass has ex excellent cellent deep drawing drawing propert! propert! and is used used or maing maing radiator ;ns.   8>, What or admiralit! brass used ? Ans: Admiralit! brass with " 5inc and 1 tin has good corrosion resistance and is used or condenser and eed heater tubes. Aluminium is also added to brass to impro#e corrosion resistance.   81. What is the maximum use o magnesium ? Ans: Magnesium is used to allo! with aluminium and as an additi#e or maing /@ */pheroidal @raphite+ iron.   8". What or 5inc ;nds applications ? Ans: @al#ani5ing consumes the largest proportion o 5inc. Ginc is resistant to corrosion but is attaced b! acids and alalies. Ginc allo!.s are suited or maing die casting since the melting point is reasonabl! low.   8&. Which actors inuence the t!pe o racture in ailure o a material ? Ans: /e#en actors inuencing t!pe o ailure are : *i+ 0!pe o material *inherent structure properties+, *ii+ Manner o loading */tatic #ersus d!namic+, *iii+ ange o imposed stress, *i#+ /train rate *static, d!namic, impact+, *#+ /tress distribution *discontinuit! in materialCshape+, *#i+ temperature, and *#ii+ surace treatment.   8(. What is the name gi#en to ratio o actual c!cle ecienc! and ideal c!cle ecienc!. Ans: cienc! ratio.   82. Eist two efects o manganese in plain carbon steels. , Ans: Manganese increases tensile strength and hardness. It decreases weldabilit!.   83. Bame the strongest and weaest t!pe o atomic bonds. Ans: Metallic bond is strongest and molecular bond also nown as 'ander Waals bond is weaest.   86. In which process internal energ! remains constant ? Ans: Isothermal process.  

 

88. What is temper embrittlement in allo! steels and what are its efects ? Ans: mbrittlement attac is usuall! intergranular in metals, i.e. cracs progress between the grains o the pol!cr!stalline material. It imparts a tendenc! to ail under a static load ater a gi#en period o time in those allo! steels which are susceptible to embrittlement.   8. What are whisers ? Ans: Whisers are #er! small cr!stals which are #irtuall! ree rom imperections and dislocations.   >. What is Dauschinger efect ? Ans: According to Dauschinger, the limit o proportionalit! o material does not remain constant but #aries according to the direction o stress under c!clic stresses.   1. What is the diference between heat capacit! and speci;c heat o a material ? Ans: 0he heat capacit! o a material is the amount o heat transormed to raise unit mass o a material 1 degree in temperature.  0he speci;c heat heat o a material is the ratio o o the amount o heat transer transerred red to raise unit mass o a material 1 degree in temperature to that re)uired to raise unit mass o water 1 degree o temperature at some speci;ed temperature. <or most engineering purposes, purposes, heat capacities ma! be assumed numericall! e)ual to%speci;c heats.   ". xplain the rule to ;nd speci;c heat o a)ueous solutions. Ans: <or a)ueous solutions solutions o salts, the speci;c heat can be estimated b! assuming the speci;c heat o the solution e)ual to that o the water alone. 0hus, or a 12 b! weight solution o sodium chloride in water, the speci;c heat would be approximatel! >.82.   &. What do !ou understand b! latent heat ? @i#e our examples o latent heats. Ans: <or pure substances, the heat efects in state at constant pressure *no temperature changeaccompan!ing being e#ident+changes are nown as latent heats. xamples o latent heats are : heat o usion, #aporisation, sublim sublimation, ation, and change in cr!stal orm.   (. 4e;ne the terms ree energ! and ree enthalp!. What is their signi;cance and importance ? Ans: <ree energ! *or elmholt5 unction+ is de;ned asCP u F0s. It is e)ual to the wor during a constantF#olume isothermal re#ersible nonow process. <ree enthalp! *or @ibbs unction+ is de;ned as g P h F 0s *where u P internal energ!, h P enthalp!, 0 P temperature, s P entrop!+ @ibbs unction is o particular importance in processes where chemical changes occur. <or re#ersible isothermal stead!Fow processes or or re#ersible constantF

 

pressure isothermal nonow processes, change in ree energ! is e)ual to net wor.   2.Which parameter remains constant in isochoric process ? Ans: 'olume.   3. What is pol!tropic process ? Onder what conditions it approaches isobaric, isothermal, and isometric process ? In which re#ersible process no wor is done ? Ans: A pol!tropic process is one that ollows the e)uation pun P constant *index n ma! ha#e #alues rom F oc to Q oo. 0his process approaches isobaric when n P >, isothermal when n P 1, and isometric when n P RxS. Bo wor is done in isometric process.   6. Whether superheated steam can be treated lie ideal gas ? Ans: Tes.   8. Hut o constant pressure and constant #olume lines on 0/ diagram which line has higher slope ? And whether slope is constant or #ariable ? Ans: 9onstant #olume line. /lope is #ariable.   . Whether entrop! is intensi#e propert! or extensi#e propert! ? Ans: ntrop! is extensi#e propert!.   1>>. In which process uid expands but does no wor ? Ans: 0hrottling process.