McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 201. |
°C. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in vacuum forming process, there is a clamp that has to be used for holding the plastic sheets. there is a heater employed for heating the mold cavity. the | |
| 202. |
Shrinkage allowance does not depend on which of the following factor? |
| A. | moulding method |
| B. | casting dimension |
| C. | pouring temperature of molten metal |
| D. | amount of finish required |
| Answer» D. amount of finish required | |
| Explanation: shrinkage allowance does not depend on the amount of finish required. the amount of finish needed on the machining portion is a factor on which machining allowance depends. shrinkage allowance depends on all other remaining factors. | |
| 203. |
The size of the sand particles in the molding sand is the biggest. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: the molding sand is made up of several particles. the properties such as porosity, texture are all considered while making it fit for the use of the foundry. out of all the materials used, the size of the sand particles (silica sand) is the highest. | |
| 204. |
The is responsible for the impact strength in the molding sand. |
| A. | aggregates |
| B. | refractoriness |
| C. | impurities |
| D. | permeability |
| Answer» A. aggregates | |
| Explanation: in a foundry, the molding sand | |
| 205. |
The property ensures the removal of excess sand in the mould box. |
| A. | adhesiveness |
| B. | cohesiveness |
| C. | green strength |
| D. | compressive strength |
| Answer» A. adhesiveness | |
| Explanation: the adhesiveness is a property of molding sand to get the stick or adhere to foreign material such as sticking of molding sand with an inner wall of the molding box. hence, as the sand sticks to the box and the excess sand is removed. | |
| 206. |
Binding property of the sand increases because of the property. |
| A. | cohesiveness |
| B. | collapsibility |
| C. | flow ability |
| D. | permeability |
| Answer» A. cohesiveness | |
| Explanation: the cohesiveness is a property of molding sand by virtue which the sand grain particles interact and attract each other | |
| 207. |
Which of the following is the most important property of the molding sand in cores? |
| A. | dry strength |
| B. | green strength |
| C. | collapsibility |
| D. | cohesiveness |
| Answer» C. collapsibility | |
| Explanation: after the molten metal in the mould gets solidified, the sand mould must be collapsible so that free contraction of the metal occurs and this would naturally avoid the tearing or cracking of the contracting metal. in absence of collapsibility property, the contraction of the metal is hindered by the mold and thus results in tears and cracks in the casting. this property is highly required in cores. | |
| 208. |
Electric arc furnaces are most suitable for which of the following type of material? |
| A. | ferrous |
| B. | non-ferrous |
| C. | both ferrous and nonferrous |
| D. | neither ferrous nor nonferrous |
| Answer» A. ferrous | |
| Explanation: electric furnaces are more suitable for ferrous material in a larger capacity. | |
| 209. |
There is no direct contact of flame and metal in which of the following type of furnace? |
| A. | cupola |
| B. | crucible |
| C. | electric arc |
| D. | induction |
| Answer» B. crucible | |
| Explanation: in crucible furnace, metal is placed in a crucible of refractory material. the crucible is heated with electric resistance. | |
| 210. |
In an induction furnace, mixing and melting rates are altered by? |
| A. | controlling the temperature ranges only |
| B. | controlling the number of electrodes used only |
| C. | controlling power and frequency of current only |
| D. | all of the mentioned factors |
| Answer» C. controlling power and frequency of current only | |
| Explanation: due to the principle of induction used, the electromagnetic fields are produced. these emf’s are used to stir the metal. hence, controlling the power and frequency, mixing and melting rates can be altered. | |
| 211. |
The machine used to mix shell mould particles consistently is |
| A. | mixer |
| B. | cupola furnace |
| C. | mueller |
| D. | mixer & cupola furnace |
| Answer» C. mueller | |
| Explanation: mueller is the machine used to mix mould particles thoroughly. | |
| 212. |
Cores used in PMC are usually made up of? |
| A. | metal |
| B. | collapsable material |
| C. | sand |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: in pmc the cores can be made out of any of these materials. | |
| 213. |
Hollow casting is the other name of which of the following special casting process? |
| A. | slush casting |
| B. | vacuum die casting |
| C. | precision investment casting |
| D. | squeeze casting |
| Answer» A. slush casting | |
| Explanation: slush casting is used to make casting which is actually hollow projections. hence, it is also called a hollow casting. | |
| 214. |
Pressure range for low pressure die casting is |
| A. | 0.3-1.5 bars |
| B. | 0.5-2 bars |
| C. | 2-6 bars |
| D. | up to 8 bars |
| Answer» A. 0.3-1.5 bars | |
| Explanation: usually the gauge is set to a range of 0.3-1.5 bars while providing pressure to the molten metal to raise it in the riser. | |
| 215. |
Dry sand cores may be required for the provision of spigot at the end section of the casting. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: when after the proper ramming of sand to confirm to the outer contour of the pipe to be made, dry sand cores may be introduced for the provision of end details such as spigot ends, or flanged ends to the casting. meanwhile there is no requirement of any cores for the making of the hollow section of the castings. | |
| 216. |
Which of the following parts is provided in between the mould and casing to reduce the vibrations? |
| A. | steel balls |
| B. | metallic roller |
| C. | viscous fluid |
| D. | grease |
| Answer» B. metallic roller | |
| Explanation: after the completion of the mould, the flask is balanced dynamically so as to reduce the occurrence of undesirable vibrations during the casting process. and the metallic rollers are used in between the rotating mould and the stationary casing to avoid the jerks and for the damping of vibrations. | |
| 217. |
In centrifugal casting, the casting yield is approximately equaled to 100%. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: there is no need for the gates and runners in the centrifugal casting process, which saves a lot of molten metal. this makes the increase in casting yield, reaching almost 100%. and no any application of cores makes the castings very economical for the large scale production. | |
| 218. |
It is also possible to make un-symmetric shape of casting in true centrifugal casting by introducing some variations to the mould. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: it is not possible to make un- symmetric shape of casting in centrifugal casting, only certain shapes which are axi- symmetric and having concentric holes are suitable to make in the centrifugal casting. and equipment are also expensive, so this method is suitable only for large scale production. | |
| 219. |
Castings made by the centrifugal casting process have negligible porosity. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in centrifugal casting, the inclusions such as slag and oxides get segregated towards the centre and can be easily removed by a machining process. and also the application of pressure on the metal throughout the solidification causes the porosity to be eliminated and gives rise to dense metal. | |
| 220. |
Which of the following types of centrifugal casting process is used for the casting, whose shape of casting is not axi- symmetric? |
| A. | true centrifugal casting |
| B. | semi centrifugal casting |
| C. | centrifuging |
| D. | full centrifugal casting |
| Answer» C. centrifuging | |
| Explanation: centrifuging is a process which is used in order to obtain higher metal pressures during solidification when the shapes of the casting are not axi-symmetrical. this process is mainly suitable for small jobs of any shape. in this method, a number of small jobs are joined together in a radial manner and then the further process of casting is done. | |
| 221. |
Co2 moulding is mainly used for the increase in strength and hardness of the moulds and cores. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: mould is prepared by adding sodium silicate binder. co2 gas is supplied to the mould for sufficient time. it reacts with sodium silicate and produces silica gel which has better bonding properties. due to this strength and hardness of the large sized moulds and cores can be increased. | |
| 222. |
Continuous passing of Co2 through the mould can decrease the strength of mould and results in a weak mould. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: continuous passing of co2 always results in a strong and hard mould. more the passing of co2 more will be the strength of the mould. only the drawback is the decrease in permeability and collapsibility of the mould. much passing of co2 gas results into difficult breathing of the mould. | |
| 223. |
Additives can be used for the non-ferrous application to avoid the poor collapsibility of the mould. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: in co2 moulding, poor collapsibility of the mould is a major disadvantage. although some additives are used for the improvement in the properties of | |
| 224. |
Sometimes over-gassing can cause the sticking of pattern to the mould in Co2 moulding. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in co2 moulding, over-gassing and under-gassing can affects the properties of cured sand adversely. when the continuous passing of co2 is done for long time, this may results into sticking of pattern with the mould which cannot be removed easily, so proper care should be taken while passing of co2 gas. | |
| 225. |
The rotor of a three phase induction motor can never attain synchronous speed. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: because then there will be no torque developed and flux cutting. | |
| 226. |
A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. How a three phase induction motor operates when rotor frequency is greater than stator frequency? |
| A. | rotor will be driven against rmf |
| B. | rotor will be driven in direction of rmf |
| C. | no emf will be induced |
| D. | the losses will be maximum |
| Answer» A. rotor will be driven against rmf | |
| Explanation: as the rotor rotates at larger speed than the stator, the rmf speed is less than the rotor speed and it tries to rotate in the opposite direction to rmf. | |
| 227. |
A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. How a three phase induction motor operates when rotor frequency is less than stator frequency? |
| A. | it operates as induction motor |
| B. | emf is induced in rotor |
| C. | rmf will rotate at synchronous speed |
| D. | all of the mentioned |
| Answer» D. all of the mentioned | |
| Explanation: it will operate as induction motor. | |
| 228. |
A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. Then the rotor emf E2 and the rotor current I2 are zero at |
| A. | ns |
| B. | 2ns |
| C. | zero |
| D. | slip of 50% |
| Answer» A. ns | |
| Explanation: the rotor emf and current are zero at the speed of synchronous speed of the machine. | |
| 229. |
Consider a situation in which a welding operation is being performed with V = 20 volts, I = 200 A, and the cross-sectional area of the weld bead is 30 mm2. Estimate the welding speed if the workpiece and electrode are made of (a) aluminum, (b) carbon steel, and (c) titanium. Use an efficiency of 75%. |
| A. | 35 mm/s |
| B. | 34.5 mm/s |
| C. | 36 mm/s |
| D. | 46 mm/s |
| Answer» B. 34.5 mm/s | |
| Explanation: for aluminum, the specific energy required is u = 2.9 j/mm3 therefore, | |
| 230. |
In arc welding, arc is created between the electrode and work by? |
| A. | contact resistance |
| B. | flow of voltage |
| C. | flow of current |
| D. | electrical energy |
| Answer» D. electrical energy | |
| Explanation: all arc welding utilizes the transfer of electrical energy to heat energy. an arc is a sustained electric discharge through this ionised gas column called plasma between the two electrodes. in order to produce the arc, the potential difference between the two electrodes (voltage) should be enough to allow them to move across the air gap. the larger air gap requires higher potential differences. if the air gap becomes too large for the voltage, the arc may be extinguished. | |
| 231. |
The coating material used for the electrode is termed as? |
| A. | flux |
| B. | slag |
| C. | protective layer |
| D. | deoxidiser |
| Answer» A. flux | |
| Explanation: flux is a substance used to prevent the formation of oxides and the other unwanted contaminations, or to dissolve them and facilitate removal. during welding the flux melts and becomes a liquid slag, covering the operation and protecting the molten weld metal the slag hardens upon cooling and must be removed later by chipping or brushing. | |
| 232. |
Which of the following welding process in which two pieces to be joined are overlapped and placed between two pointed electrodes? |
| A. | seam welding |
| B. | resistance welding |
| C. | projection welding |
| D. | spot welding |
| Answer» D. spot welding | |
| Explanation: spot welding is the simplest and most used resistance welding process. welding may be performed by means of single (most common) or multiple pairs of electrodes (as many as a hundred or more), and the required pressure is supplied through mechanical or pneumatic means. | |
| 233. |
In which of the following type of flame, oxygen is of same proportion with acetylene? |
| A. | neutral flame |
| B. | oxidizing flame |
| C. | carburizing flame |
| D. | both oxidizing flame and carburizing flame |
| Answer» A. neutral flame | |
| Explanation: in neutral flame oxygen is in the same proportion with acetylene. neutral welding flames are commonly used to weld: mild steel, stainless steel, cast iron, copper, aluminium, etc. | |
| 234. |
If the open circuit voltage is 60 volt and the short circuit current is 20 amperes. Then determine the voltage required for welding if the current required during welding is 10 amperes? |
| A. | 30 v |
| B. | 60 v |
| C. | 20 v |
| D. | 40 v |
| Answer» A. 30 v | |
| Explanation: voltage = ocv – ( i )×ocv, where “ocv” is open circuit voltasgcec, “scc” | |
| 235. |
How does the arc voltage V depends upon the length of arc L? |
| A. | v = f(l) |
| B. | v = 1/f(l) |
| C. | v = f(l2) |
| D. | v = f(√l) |
| Answer» A. v = f(l) | |
| Explanation: v= a+bl, where ‘v’ is the arc voltage and ‘l’ is the length of arc in cm, a & b are constants. | |
| 236. |
What is the only difference between Plasma arc welding and TIG welding? |
| A. | flux is not used |
| B. | construction of torch is different |
| C. | gas is not used |
| D. | tungsten electrode is not used |
| Answer» B. construction of torch is different | |
| Explanation: construction of the torch is the only difference between plasma arc welding and tig welding. both the tig and paw are uses tungsten electrodes. | |
| 237. |
In plasma arc welding the gas is? |
| A. | ionized |
| B. | heated |
| C. | magnetized |
| D. | vaporized |
| Answer» A. ionized | |
| Explanation: in plasma arc welding the gas is ionized. electrode used is made of tungsten and filler metal is used addition to it. | |
| 238. |
Which of the following inert gas is used with DC power supply only? |
| A. | argon |
| B. | helium |
| C. | co2 |
| D. | nitrogen |
| Answer» C. co2 | |
| Explanation: co2 is used only in dc power supply. it cannot be used in ac power supply. argon and helium can be used with ac supply. | |
| 239. |
Which kind of resistance is experienced in upset butt welding? |
| A. | electric resistance |
| B. | magnetic resistance |
| C. | thermal resistance |
| D. | air resistance |
| Answer» A. electric resistance | |
| Explanation: in the making of an upset butt welding, there are jaws made of copper, into which the part to be welded is put, and hence a solid contact is made. at this point of contact, while the current flows, it gets transformed into heat because of electric resistance. | |
| 240. |
How are the metals to be welded connected to each other in spot welding? |
| A. | electric contact |
| B. | magnetic field |
| C. | mechanical pressure |
| D. | direct contact |
| Answer» C. mechanical pressure | |
| Explanation: in spot welding process, the metal or the alloy parts which are to be welded, are heated in their in their zones. to bring these parts in contact with one another, mechanical pressure is applied, causing them to connect. | |
| 241. |
Up to what thickness, can steel be welded using spot welding process? |
| A. | 10 mm |
| B. | 11 mm |
| C. | 12 mm |
| D. | 13 mm |
| Answer» C. 12 mm | |
| Explanation: in spot welding process, to bring the heated parts in contact with one another, mechanical pressure is applied. this pressure can be of three types, by using foot lever, by providing air pressure or by using a hydraulic cylinder. the use of these methods allows steel or other metal parts to be welded up to a thickness of 12 mm. | |
| 242. |
In flash butt welding, the forced out metal is called flash. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: in flash butt welding process, there is a light contact between the edges. a high voltage is supplied when the flashing action takes place. in this process, the metal that is forced out, is called as flash. | |
| 243. |
In friction welding process, materials are joined by motion between materials. |
| A. | rectilinear |
| B. | rubbing |
| C. | translatory |
| D. | brownian |
| Answer» B. rubbing | |
| Explanation: friction welding is a solid-state joining process that produces coalescence in materials, using the heat developed between surfaces through a combination of mechanically induced rubbing motion and applied load. the resulting joint is of forged quality. | |
| 244. |
All metallic engineering materials which are can be friction welded. |
| A. | soft |
| B. | weldable |
| C. | forgeable |
| D. | metamaterials |
| Answer» C. forgeable | |
| Explanation: as a rule, all metallic | |
| 245. |
Friction welding is process. |
| A. | costly |
| B. | cost saving |
| C. | time consuming |
| D. | highly material selective |
| Answer» B. cost saving | |
| Explanation: since dissimilar materials can be joined, a significant cost savings are possible because engineers can design bimetallic parts that use expensive materials only where needed. expensive forgings and castings can be replaced with less expensive forgings welded to bar stock, tubes, plates and the like. | |
| 246. |
Friction welding produces quality joints, with a 100% weld. |
| A. | lap joint |
| B. | tee-joint |
| C. | butt joint |
| D. | edge joint |
| Answer» C. butt joint | |
| Explanation: friction welding produces forged quality joints, with a 100% butt joint weld through the contact area. furthermore, in friction welding heat affected zone is much narrower as compared to other welds, which indeed reduces the cost of post-weld heat treatments (stress relieving processes). | |
| 247. |
In inertia friction welding energy of welding machine is used. |
| A. | electrical |
| B. | potential |
| C. | rotational |
| D. | frictional |
| Answer» C. rotational | |
| Explanation: inertia friction welding is a variation of friction welding in which the energy required to make the weld is supplied primarily by the stored rotational kinetic energy of the welding machine. | |
| 248. |
In inertia friction welding, one workpiece is connected to |
| A. | flywheel |
| B. | the pin tool |
| C. | rotor |
| D. | generator |
| Answer» A. flywheel | |
| Explanation: in inertia welding, one of the workpieces is connected to a flywheel and the other is restrained from rotating. the flywheel is accelerated to a predetermined rotational speed, storing the required energy. the drive motor is disengaged and workpieces are forced together by the friction welding force. | |
| 249. |
Which of the following defects occur when weld metal layer fails to fuse together? |
| A. | inclusion of slag |
| B. | inadequate penetration |
| C. | incomplete fusion |
| D. | porosity |
| Answer» C. incomplete fusion | |
| Explanation: incomplete fusion defects occur when weld metal layer fails to fuse together. it causes discontinuity in weld zone. | |
| 250. |
Which of the following defects occur due to melting or burning away of base metal? |
| A. | undercut |
| B. | spatter |
| C. | cracking in weld metal |
| D. | cold cracking |
| Answer» A. undercut | |
| Explanation: undercut is the cardinal sin of welding grasshopper! cutting into the steel with the force of the arc leaves a cut out groove in the weld. if this is not filled back in with filler metal, it leaves a weld defect which is a weak point that can cause the joint to fail. this can cause property damage, injury and even loss of life. | |
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