TNPSC Combined Technical Service Exam Objective types questions with answers 2026-27
1.Among the common dielectric materials, the highest dielectric strength is possessed by?
Ans: Mica
2.casting which rocess produces lowest surface roughness?
Ans: Die casting
3.Vacancy and Interstitial defects are classified under which type of crystal defect?
Ans: Point defects
4.Near net shape manufacturing in powder metallurgy leads to?
Ans: No scrap
5.For the extremely sensitive flourescent detection of cracks and surface discontinuities which of the following method is recommended?
Ans: Zyglo penetrant inspection method
6.Economical method of surface hardening for large machine parts is?
Ans: Flame hardening
7.Ability of the material to absorb energy during plastic deformation upto fracture is called as?
Ans: Toughness
8.Extensometer is used to measure the?
Ans: Elongation
9.The grain size of the material is controlled by several factors out of which factors are more important.?
Ans: Temperature and time of heating
10.The Melting Point of Pure Iron is?
Ans: 1539°C
11.Process of bonding solid bodies by atomic forces is called as?
Ans: Sintering
12.The hardness of martensite in a steel is a function of?
Ans: Carbon content
13.Gun metal is an alloy of?
Ans: Copper, Tin and Zine
14.The hardening of machine tool guideways is usually done by?
Ans: Flame hardening
15.The solubility limit of Carbon in Iron-Iron Carbide diagram is?
Ans: 6.67%
16.Super alloys are alloys having any one of the following metals predominantly?
Ans: Iron, Nickel and Cobalt
17.Which material is characterised by hystersis?
Ans: Ferromagnetic Material
18.The bulkiest side group in the monomer is in
Ans: Polystyrene
19.Conductors will have the Electrical resistivity in the range of
Ans: 10-9 to 10-3 ohm.m
20.The main advantage of using powder metallurgy for producing complex shapes is
Ans: Reduced material wastage
21.Examples of low density materials used in structural applications are
Ans: Metallic foams, cellular materials
22.The unit cell structure of Martensite in Iron Carbon Alloy is
Ans: Body Centered Tetragonal (BCT)
23.Ledeburite is formed at a temperature of>?
Ans: 2065°F
24.Which of the following function does not come under staffing?
Ans: Motivation
25.Which one of the following does not come under research phase in the operation research?
Ans: Determination of type of problem, its origin and cause
26.The end of a beam is hinged to the support, the reaction on such end acts as?
Ans: horizontal, vertical & inclined
27.A circular roller of weight 100 N and radius 10 cm hangs by a tie rod AB = 20 cm and angle to the vertical and rests against a smooth vertical wall at C. Determine the force F in the tie rod?
Ans: 115.47 N
28.The Bending Moment on a section is maximum where shearing force is?
Ans: changing sign
29.Which statement is not relevant to ‘Weight’?
Ans: It is constant at all places
30.Maximum efficiency of a series of vertical plates is?
Ans: 50%
31.A plane is stated to move horizontally relative to the ground at aspeed of twich the sound velocity (a = 340 m/s) and that the air ismoving in the opposite direction with speed equal to one-half thesonic velocity relative to the ground. The value of Mach number is?
Ans: 2.5
32.The performance of specific task in CPM is known as?
Ans: Activity
33.Which method gives the better Solution for transportation problem?
Ans: Vogel Approximation Method
34.Work study is concerned with?
Ans: Improving present method and finding standard time
35.In scheduling, the term “makespan” refer to?
Ans: Time taken to complete the last job
36.For self locking of screws, the efficiency of screws should be?
Ans: less than 50%
37.The velocity and acceleration of the reciprocating parts of an Internal Combustion Engine can be determined by?
Ans: Ritterhaus’s Construction
38.The maximum amount of primary unbalanced force perpendicular to the line of stroke is known as?
Ans: Hammer blow
39.If two making links have a turning as well as sliding motion between them then it is known as?
Ans: Screw Pair
40.A compound mechanism consist of______links?
Ans: More than Four
41.The efficiency of a free jet striking normally on a series of flat plates mounted on the periphery of a wheel can never exceed?
Ans: 50%
42.Governing of a turbine means?
Ans: The speed is kept constant under all conditions of working
43.Main characteristic curves of a turbine means?
Ans: rves at constant head
44.A control volume refers to?
Ans: A fixed region in space
45.When subjected to shear force, a fluid?
Ans: deforms continuously no matter how small the shear stress may be
46.If the velocity in a fluid does not change with respect to length of direction of flow then it is called as?
Ans: Uniform flow
47.A statistical process control chart which shows the number of defects found in a subgroup of fixed size is?
Ans: C-chart
48.The test applied to determine whether or not there is a significant difference between the means of two related lots.?
Ans: Paired t-Test
49.The control chart for the average number of defects per unit, when the subgroup sizes are variable is?
Ans: U Chart
50.A material that develops electrical output when it is compressed is said to exhibit?
Ans: Piezoelectric property
51.Guide angle as per the aerofoil theory of Kaplan turbine blade design is defined as the angle between?
Ans: Lift and Resultant force
52.In axial flow turbines, the fluid enters and leaves as follows?
Ans: Axially, Axially
53.Cavitation damage in turbine runner occurs near the?
Ans: Outlet on the convex side of blades
54.The dimensions of Thermal Conductivity is?
Ans: MLT-3Q-1
55.Principle of similitude forms the basis of?
Ans: Designing models so that the result can be converted to prototypes
56.The boundary layer separation takes place if?
Ans: Pressure Gradient is positive
57.A heat pump delivers heat at the rate of 200 MJ/h to a room. If the coefficient of performance of the pump is 4.0. Determine the power required to run the pump?
Ans: 14.00 KW
58.А Heat Pump operating on Carnot Cycle pumps heat from areservoir at 300 K to a reservoir at 600 K. The co-efficient ofperformance is?
Ans: 2
59.Ozone depletion is caused due to?
Ans: Use of CFC
60.In a Psychrometric Chart, cooling and humidification process represented by a?
Ans: line parallel to wet bulb temperature
61.A ideal diesel engine has a diameter of 15 cm and stroke 20 cm. Theclearance volume is 10% at the swept volume. Determine thecompression ratio of the engine?
Ans: 11
62.An engine 20 cm bone and 30 cm stroke works on Otto Cycle. Theclearance volume is 1600 cu cm and v = 1.4. Determine the airstandard efficiency of the cycle?
Ans: 54.08%
63.Hydraulic Gradient line represents the sum of?
Ans: Pressure Head and Datum Head
64.The form error on a machined surface results due to?
Ans: Moving bridge type
65.Which image processing technique is used to account for poor illumination and lack of dynamic range in the image sensor??
Ans: Contrast stretching
66.According to the “rule of ten” in measurements?
Ans: The discrimination of the instrument should divide the tolerance into 10 parts
67.A cylindrical tolerance zone circumscribed about a square tolerance zone has -% more area than the square tolerance zone.?
Ans: 57%
68.Identify the reason for strain-gauges having high value of gauge factor?
Ans: To increase the sensitivity
69.As a general practice, the suction lift for a centrifugal pump is restricted to?
Ans: 6 to 7 m
70.The surface tension of mercury at normal temperature when compared to that of water is?
Ans: more
71.The rise of oil in the wick of an oil lamp may be attributed to?
Ans: Capillary action
72.Identify the tester in which the gear being inspected is made to mesh with a standard gear and a dial indicator is used to capture the radial errors.?
Ans: Parkinson gear tester
73.In the hole and shaft pair designation of 40 H7/d9, the numbers 7 and 9 indicate?
Ans: Tolerance grade
74.What does the Coefficient Of Performance (COP) represent in refrigeration or heat pump system?
Ans: The ratio of useful heat to work input
75.Which property of moist air is defined as the temperature at which air becomes saturated with moisture??
Ans: ew point temperature
76.The efficiency of an Otto Cycle is 60% and y = 1.5. What is the compression ratio??
Ans: 6.25
77.For the same maximum pressure and temperature of Otto, Diesel and Dual Combustion air standard cycles?
Ans: Heat rejected by the cycles is same
78.In an ideal combustion reaction, what happens to the adiabatic flame temperature if the fuel is completely burned with no excess air?
Ans: It increases
79.During the dryness fraction measurement using throttling calorimeter the wet state of steam is throttled so as to lie in?
Ans: Superheated state
80.The component of Acceleration due to non-uniformity of flow is called?
Ans: Convective Acceleration
81.The thin film material which is used for preparation of photovoltaics or solar cells is?
Ans: Amorphous silicon
82.Which law states that the volume of a gas is inversely proportional to its pressure at constant temperature?
Ans: Boyle’s Law
83.Equation for Gibbs function.?
Ans: G= H -TS
84.A refrigerating machine having coefficient of performance 2 is used to remove heat at the rate of 1200 kJ/min. What is the power required to run the machine?
Ans: 10 kW
85.Which one of the following is not belongs to fusion welding?
Ans: Ultrasonic Welding
86.Туpіcally forged components exhibit resistant to impact damage and resistant to deformation because?
Ans: Flow of grains aligns with the shape
87.Fabrication Weldability Test is used to determine?
Ans: Susceptibility of welded joint for cracking
88.For resistance welding?
Ans: Voltage is low, current is high
89.Phenol-formaldehyde is a type of?
Ans: Thermosetting material
90.The basis for measuring thermodynamic property of temperature is given by
Ans: Zeroth Law of Thermodynamics
91.Micro-EDM is a process of material removal by?
Ans: Melting (or) vaporisation
92.A block of information in N.C. machine program means?
Ans: one complete instruction
93.The abrasive particles in the abrasive water-jet machining causes?
Ans: increase in the material removal rate above that of water jet machining
94.In Ultrasonic Machining material is removed from the workpiece by?
Ans: Vibrating the tool
95.An isolated system is containing 1.5 kg of liquid having a specific heat of 2.5 kJ/kg-K, find the heat transfer.?
Ans: Zero kJ/kg
96.What is the first law of thermodynamics?
Ans: Energy cannot be created or destroyed, only transformed
97.In a heat engine operating between two temperatures, what happens to some energy during the conversion of heat to work?
Ans: It is lost as waste to the cold reservoir
98.In a system absorbs 500 J of heat and does 200 J of work on the surroundings, what is the change in internal energy of the system?
Ans: 300 J
99.What is the main characteristic of an isolated system compared to other types of thermodynamic systems?
Ans: It allows neither mass nor energy transfer
100.А PMM 1 is?
Ans: A hypothetical machine whose operation would violate the First Law of Thermodynamics
101.What will be the point angle of a drill while drilling wood and soft materials?
Ans: 60°
102.The generally prescribed surface speed of soft silicate bond grinding wheel is?
Ans: 23-28 m/s
103.A hole is being drilled in a block of magnesium alloy with a 10 mm drill bit at a feed of 0.2 mm/rev and N = 800 rpm. Calculate the MRR?
Ans: 12570 mm3/min
104.Which joint is primarily used in the construction of pipelines?
Ans: Butt joint
105.The presence of sulphur and phosphorus promotes steel?
Ans: Hot cracking
106.Cold working of metals should be done at which temperature.?
Ans: Below recrystalisation
107.Which one of the following is a negative allowance in pattern making?
Ans: Rapping allowance
108.Radiation heat transfer is characterized by
Ans: Movement of discrete packets of energy as electromagnetic waves
109.What does the shape factor represent in radiation heat transfer?
Ans: The geometry of the surfaces involved
110.Which of the following law of thermodynamics is responsible for heat transfer?
Ans: Second law of thermodynamics
111.Peclet number is expressed as
Ans: Reynolds number x Prandtl number
112.The Prandtl Number (P,.) is the ratio of
Ans: Kinematic Viscosity to thermal diffusivity
113.Which of the following is NOT a mode of heat transfer?
Ans: Expansion
114.Upto critical radius of insulation?
Ans: Added insulation increases heat loss
115.On heat transfer surface, fins are provided
Ans: To increase surface area to increase the rate of heat transfer
116.In the electrical analogy of heat transfer, which property is analogous to temperature difference?
Ans: Voltage
117.A numerical analysis method for obtaining approximate solutions to a wide variety of engineering problems is?
Ans: Finite Element Method
118.Which one of the following is correct for networking standardization and their development for application layer?
Ans: User specific application software
119.To improve the directional solidification for complicated casting geometries, _ are provided in the mould.?
Ans: Chill
I20.n solidification of metal during casting, compensation for solid contraction is?
Ans: Provided by the oversize pattern
121.The ratio of a mass density of species A to the total mass density of the mixture is known as?
Ans: Mass fraction
122.Concentration boundary layer is used to determine?
Ans: Convective mass transfer coefficient
123.Which of the following is a mode of heat transfer that does not require a medium to propagate?
Ans: Radiation
124.In a counter flow heat exchanger, the hot Fluid and the cold Fluid flow?
Ans: In opposite directions
125.For evaporators and condensers for the given conditions, the Logarthmic Mean Temperature Difference (LMTD) for parallel flow is?
Ans: Smaller than that for counter flow
126.In the manufacturing process group technology brings together and organizes?
Ans: Similar Parts, batches and problems
127.The speed at which robot is capable of manipulating its end effector is known as the?
Ans: Speed of movement
128.All triangle co-ordinates within an STL file must be?
Ans: Positive
129.In threaded joints, BSW stands for?
Ans: British Standard Whitworth
130.In a helical compression spring with square and ground ends, the number of active turns is equal to if the total number of coils is N.?
Ans: N-2
131.Two plates of width 12 cm and thickness 1.15 cm are welded by a single V-butt joint. If the safe stress in the weld is 140 N/mm², find the permissible load carried by the plates.?
Ans: 210 kN
132.The maximum fluctuation of energy is the
Ans: Difference between maximum and minimum energies
133.In a solid circular shaft, the maximum shear stress occurs at which location?
Ans: At the surface of the shaft
134.The maximum slope of a cantilever carrying a point load at its free end is at the?
Ans: Free end
135.A simply supported beam AB of span (1) carries a point load (W) at C at a distance (a) from the left end A, such that a<b. The maximum deflection will be?
Ans: between C and B
136.When a solid shaft is subjected to torsion, the shear stress induced in the shaft at its centre is?
Ans: Zero
137.A large uniform plate containing a rivet hole subjected to uniform uniaxial tension of 95 MPa. The maximum stress in the plate is?
Ans: 285 MPa
138.Proof Resilience is the Mechanical property of materials that indicates their capacity to bear the
Ans: shocks
139.The stress at which elongation of a material is quite large as compared to the increase in load is known as?
Ans: yield point
140.The ratio of normal stress of each face of a solid cube to volumetric strain is called?
Ans: Volume modulus of elasticity
141.An approach used in the product development which combines the efforts of design, manufacturing and other functions to reduce the total time in introducing a new product in the market is?
Ans: Concurrent Engineering
142.Functional areas of a CAD Design Process are?
Ans: Geometric Modeling
143.The term “tolerance” in mechanical assembly refer to
Ans: The allowable variation in dimension
144.The primary purpose of Geometric Modelling in Mechanical Engineering focus on
Ans: Defining the shape and structure of parts and assemblies
145.Oldham coupling is used to connect two shafts?
Ans: which have lateral misalignment
146.In designing a connecting rod, it is considered like buckling about X-axis.
Ans: both ends hinged
147.In a 6×20 wire rope No. 6 indicate that
Ans: Number of strands
148.hat is meant by “fatigue limit” in the context of design?
Ans: The maximum load a material can endure for an infinite number of cycles