An ideal gas at 27ºC is heated at constant pressure till its volume becomes three times. What would be then the temperature of gas?
T1 = 27 +273 =300 K
use P1V1/T1 = P2V2/T2
GIVEN P1 =P2
SO V1/T1 =V2/T2
V/300 = 3V/T2
Measurement of temperature is based on which law of thermo dynamics?
Law of thermodynamics is the basis for measurement of temperature and setting its scale. In simple word, Zeroth law of thermodynamics says that “When two bodies are separately in thermal equilibrium with the third body, then the two are also in thermal equilibrium with each other.”
Hot coffee stored in a well insulated thermos flask is an example of
As the hot coffee remains hot for a long time so neither heat nor mass is exchanged with the surroundings and hence it is an example of isolated system.
Which one of the following expresses the reversible work done by the system (steady flow)
between states 1 and 2?
A closed system receives 60 kJ heat but its internal energy decreases by 30 kJ. Then the work done by the system is
Qsupplied = 60KJ
du= -30 KJ
from first law of thermo=
dQ = du + dW
60 = -30 + dW
dW = 90 KJ
Work transfer between the system and the surroundings
The work is the path function so the work transfer between the system and the surrounding depend on the path that followed by tha system.
The value of for an irreversible cycle is
One Joule (J) is equal to
1 joule (J) = 1.00 newton meters (N-m)
The temperature at which the volume of a gas becomes zero is called
General gas equation
at absolute zero kelvin temp.
therefore volume will be zero at absolute zero kelvin temp.
The molecular mass expressed in gram (i.e. 1 gmole) of all gases, at N. T. P., occupies a volume of
According to Avogadro's law ,the volume of a gram mole of all gases at the pressure of 760 mm of Hg and temperature of 0 degree centigrade is same and is equal to 22.4 litres.
The sum of internal energy (U) and the product of pressure and volume (p.v) is known as
dU + PdV = dH which is enthalpy
Carnot cycle has maximum efficiency for
No engine working between two given temperatures can be more efficient than a reversible engine working between the same two temperatures and that all the reversible engines working between the same two temperatures have the same efficiency, whatever the working substance may be.
A refrigeration system
The C.O.P. of a refrigerator working on a reversed Carnot cycle is where
T1 = Lowest absolute temperature, and
T2 = Highest absolute temperature
The leakage in a refrigeration system using freon is detected by
The leaks in a refrigeration system using Freon are detected by Halide torch which on detection produces greenish flame lighting
The COP of a heat pump βhp and the COP of a refrigerator βRef are related as
In electrolux refrigerator
The hydrogen passes across the surface of the ammonia. It lowers the ammonia vapor pressure enough to allow the liquid ammonia to evaporate. The evaporation of the ammonia extracts heat from the evaporator. This, in turn, extracts heat from the food storage space, lowering the temperature inside the refrigerator.
The correct sequence of the given four cycles on T-s plane in figure 1, 2, 3, 4 is
An Otto cycle has a compression ratio of 8. If 250 kJ of work is extracted from the cycle, the heat rejected by the cycle is
The two reference fuels used for cetane rating are
Cetane and alpha-methyl naphthalene are the reference fuels taken for cetane rating.
The stoichiometric air-fuel ratio for petrol is 15 :1. What is the air-fuel ratio regarded for maximum power ?
For maximum power, slightly rich mixture is required in order to burn more fuel and get energy.
Match List-I (SI Engine Operating Mode) with List –II (Appromimate A/F Ratio) and select the correct answer using the code given below the lists
A spark plug gap is kept from
A spark plug gap is kept from- 0.3-0.7 mm because 0.3-0.7 is perfect gap for making spark in spark plug.
The ignition quality of petrol is expressed by
Ignition quality of petrol is expressed by octane number and that of diesel by cetane number.
Which of the following is not a boiler mounting?
Economizer is boiler accessory and others are mounting
The function of a safety valve is
An air preheater is installed
Match List-I (Type of boiler) with List-II (Classification of boiler) select the correct answer
using the codes given below the lists:
Benson boiler is one of the high pressure boilers having
The draught in locomotive boilers is produced by
The function of economizer in a boiler is to
Boiler Economiser ( Sometimes Called Economizer ) is the Energy improving device that helps to reduce the cost of operation by saving the fuel. In boilers, economizers are generally Heat Exchangers which are designed to exchange heat with the fluid, generally water.
The critical pressure ratio for maximum discharge through a nozzle is given by
Surging basically implies
Surging is caused due to unsteady, periodic and reversal of flow through the compressor when the compressor has to operate at less mass flow rate than a predetermined value
Phenomenon of chocking in compressor means
Choking is the condition which occurs in the compressor in which it operates at very high mass flow rate and flow through the compressor can't be further increased as mach number at some part of the compressor reach to unity i.e. to sonic velocity and the flow is said to be choked.
The instantaneous centre of rotation of a rigid thin disc rolling on a plane rigid surface is located at
A four-bar chain has
Which one of thefollowing conversions is used by a lawn-sprinkler which is a four barme chanisms?
Which one of the following drives is used for a constant velocity ratio, positive drive with large centre distance between the driver and driven shafts?
The number of degrees of freedom of an epicyclic gear train is
1 DOF - when the sun is constant and planet is roatating as well as revolving around sun and arm rotating.
2 DOF - when sun and arm are rotating and planet is rotating as well as revolving around sun.
In which one of the following is a fly wheel generally employed?
The motion between a pair when limited to a definite direction, irrespective of the direction of force, applied, is known as
Completely constrained motion is a type of constrained motion in which relative motion between the links of a kinematic pair occurs in a definite direction by itself, irrespective of the external forces applied.
Which of the following is an example of a higher pair?
The relation between number of pairs (P) forming a kinematic chain and the number of links (l)
The design calculations for members subject to fluctuating loads with the same factor of safety yield the most conservative estimates when using
Correct Answer :- b
Explanation : The Soderberg line is a more conservative failure criterion and there is no need to consider even yielding in this case.
When a nut is tightened by placing a washer below it the bolt will be subjected to
In a fillet welded joint, the weakest area of the weld is
18/8 steel contains
18/8 stainless steel is nominally 18% chromium and 8% nickel, with the remainder being mainly iron; it does however also contain other elements, but at very low levels. It is also known as 302 or 304 grade stainless steel.
An aluminium member is designed on the basis of
Guest's theory is used for
MAXIMUM SHEAR STRESS THEORY (GUEST's or TRESCA's THEORY)
According to this theory, the elastic failure occurs when the greatest shear stress reaches a value equal to the shear stress at elastic limit in a simple tension test. This is used for ductile material
The notch sensitivity q is expressed in terms of fatigue stress concentration factor Kf and theoretical stress concentration factor Kv as
The dimensions of surface tension are
surface tension is often expressed as an amount of force exerted in the surface perpendicular to a line of unit length. The unit then is newtons per metre, which is equivalent to joules per square metre.
If the surface tension of water air interface is 0.073 N/m, the gauge pressure inside a rain drop
of 1 mm diameter will be
When can a piezometer be not used for pressure measurement in pipes?
Three immiscible liquids of specific densities ρ , 2ρ and 3ρ are kept in a jar. The height of the liquids in the jar and at the piezo meter fitted to the bottom of the jar are as shown in the figure below.
The ratio H/h is.
The critical value of Reynolds number for transition from laminar to turbulent boundary layer in external flows is taken as
For flow over a flat plate, transition from laminar to turbulent boundary layer occurs when Reynolds number at x exceeds Rex,crit ~ 500,000. Transition may occur earlier, but it is dependent especially on the surface roughness.
The head loss in turbulent flow in pipe varies
Laminar flow between closely spaced parallel plates is governed by the consideration of which one of the following pair of forces?
A centrifugal pump gives maximum efficiency when its blades are
The efficiency of a centrifugal pump will be maximum when the blades are bent backward.
A manometer is used to measure
When a body is placed over a liquid, it will float if
Gravitational force i.e. weight should be less than the upthrust force for a body to float
The discharge through a large rectangular orifice is given by
where H1= Height of the liquid above the top of the orifice,
H2= Height of the liquid abvoe the bottom of the orifice,
b = Breadth of the orifice, and
Cd= Coefficient of discharge
The coefficient of viscosity may be determined by
The unit discharge through the turbine is
The deformation of a bar under its own weight as compared to that when subjected to a direct axial load equal to its own weight will be
Actually the deformation under a conectrated load P at end will give deformation equals to PL/AE.
The deformation due to self weight is is give by PL/2AE.
What is the relationship between the linear elastic properties; Young's modulus (E), rigidity modulus
(G) and bulk modulus (K)?
Which one of the following mohr's circles represents the state of pure shear?
For pure shear, radius is equal to shear stress and the centre lies on the point of intersection of axes.
Auto frettage is the method of
A simply supported beam is loaded as shown in the figure below.
The maximum shear force in the beam will be
The ratio of the compressive critical load for a long column fixed at both the ends and a column with one end fixed and the other end free is
A short column of external diameter D and internal diameter d carries an eccentric load W.
The greatest eccentricity which the load can be applied without producing tension on the crosssection of the column would be
The Poisson's ratio for cast iron varies from
The relation between Young's modulus (E), shear modulus (C) and bulk modulus (K) is given by
The point of contraflexure occurs in
The slenderness ratio is the ratio of
Fatigue test is carried out for
According to lami's theorem
A couple produces
A couple in mechanics refers to two equal forces that act in opposite direction . The resultant force in a couple is zero, but it does have a moment of force(torque).A couple produces rotational motion in the object it is acting.
The ratio of static friction to dynamic friction is always
The static friction is always greater than the dynamic friction and hence the ratio of a bigger number to a smaller number is more than 1
A framed structure as shown fig. is a
A framed structure is perfect, if the number of members are equal to ( 2 n- 3) , where n is the no. of joints. In this figure, there are 3 joints ,therefore, (2*3-3) = 3
That means there are three members , so it is a perfect frame.
Eutectoid reaction occurs at
In eutectoid reaction, the austenite transforms into a phase mixture of ferrite (containing 0.76% C) and cementite. This phase mixture is known as pearlite. The eutectoid reaction occurs at a constant temperature. This is known as eutectoid temperature and is 723oC
Addition of magnesium to cast iron increases its
Magnesium is a powerful inoculant in cast iron. When added in concentrations exceeding 0.04%, it produces a spheroidal form of graphite that improves the iron's strength and ductility. Magnesium is an abundant metal with a price roughly comparable to that of aluminum, albeit usually higher
Consider the following quenching media:
The correct sequence of these media in order of increasing hardness of steel under going heat treatment is
Correct Answer :- c
Explanation : Quenching Media
Four commonly used quenching media are :
1.Oil - slowest cooling rate
2. Water - moderate cooling rate
3. Brine - the fastest cooling rate
4. Liquid Nitrogen - used in automatic furnaces, can be very fast cooling.
Gunmetal, which is used in journal bearings, contains
A sand casting mould assembly is shown in the given figure. The elements marked A and B are respectively
The process of removing the burrs of flash from a forged component in drop forging is called
Trimming is a manufacturing process that is used as a finishing operation for forged parts, in order to remove flash. Flash is a characteristic common in most metal forgings. For that reason trimming, while not technically a forging or even a forming operation in general, is discussed in this section. Trimming basically presses a part through a cutting die that runs the periphery of the work. The cutting die are precisely designed to remove the flash from a particular part. Most often it is desirable to perform this operation while the work is still hot for maximum efficiency, therefore it is usually incorporated into the larger production process. For more delicate forgings, flash can be ground or cut off using different methods. For certain metal forgings, this is an extremely quick and easy method for the removal of the extra material.
Which one of the following processes is the wire drawing process?
High speed electron beam of electron beam welding is focused on the weld spot using
The ratio between Oxygen and Acetylene gases for neutral flame in gas welding is
The neutral flame has a one-to-one ratio of acetylene and oxygen. It obtains additional oxygen from the air and provides complete combustion. It is generally preferred for welding. The neutral flame has a clear, well-defined, or luminous cone indicating that combustion is complete
The instrument or device used to measure the cutting forces in machings is
Which of the following property is desirable in parts subjected to shock and impact loads?
Correct Answer :- d
Explanation : Wrought iron is an iron alloy with very low carbon content with respect to cast iron. It is soft, ductile, magnetic, and has high elasticity and tensile strength. It can be heated and reheated and worked into various shapes.
18 - 4 - 1 high speed steel contains
The type of tool used on lathe, shaper and planer is
Flank wear occurs mainly on the
Cutting fluids are used to
The tool life is said to be over if
A mandrel is used to hold
Mandrel is used to hold a hollow bar or a bar with a bore wen turning between live centre and dead cente of a lathe. A moving mandrel is also used for tube drawing
In a planer
On the planer the work is moved against a stationary tool: on the shaper the tool moves across the work, which is stationary. On the planer the tool is fed into the work; on the shaper the work is usually fed across the tool. The drive on the planer table is either by gears or by hydraulic means.
Surface grinding is done to produce
Surface grinding is used to produce a smooth finish on flat surfaces. It is a widely used abrasive machining process in which a spinning wheel covered in rough particles (grinding wheel) cuts chips of metallic or nonmetallic substance from a workpiece, making a face of it flat or smooth.
A simply supported beam 'A' of length l, breadth b and depth d carries a central load W. Another beam 'B' of the same dimensions carries a central load equal to 2 W. The deflection of beam 'B' will be __________ as that of beam 'A'.