Question Bank
OPSC AAE (Paper-I) Exam - English
Duration: 120 · Questions: 100 · Max Marks: 100 · Language: 3
General Engineering
1
At temperature of 298 Kelvin, Silicon is not suitable for most-electronic applications, due to small amount of conductivity. This can be altered by
2
By doping Germanium with Gallium, the types of semi-conductors formed are
1. N type
2. P type
3. Intrinsic
4. Extrinsic
1. N type
2. P type
3. Intrinsic
4. Extrinsic
3
An n-type of silicon can be formed by adding impurity of:
1. Phosphorous
2. Arsenic
3. Boron
4. Aluminum
Which of the above are correct ?
1. Phosphorous
2. Arsenic
3. Boron
4. Aluminum
Which of the above are correct ?
4
According to Einstein’s relationship for a semiconductor, the ratio of diffusion constant to the mobility of the charge carriers is
5
Swept-out voltage in PIN diode happens when PIN diode is
6
The number of holes in an N-type silicon with intrinsic value 1.5 × 1010/cm3 and doping concentration of 1017/cm3, by using mass-action law is
7
A tunnel-diode is best suited for
8
Small recovery time of a diode is most significant for
9
In JFET, when operated above the pinch-off voltage, the
10
Thermal runaway is not possible in FET because, as the temperature of FET increases
11
Consider the following statements regarding an N-P-N Bipolar Junction Transistor:
1. Emitter diode is forward biased and collector diode is reverse biased
2. Emitter has many free electrons
3. Free electrons are injected into base and pass through collector
4. Depletion layers around junction J1 and J2 of BJT are widened
Which of the above statements are correct?
1. Emitter diode is forward biased and collector diode is reverse biased
2. Emitter has many free electrons
3. Free electrons are injected into base and pass through collector
4. Depletion layers around junction J1 and J2 of BJT are widened
Which of the above statements are correct?
12
A freewheeling diode T phase controlled rectifier
13
The zeners incorporated within the encapsulations of some MOSFETs are meant for
14
When UJT is used for triggering an SCR, the wave-shape of the signal obtained from UJT circuit is
15
Darlington pairs are frequently used in linear ICs because, they
16
Which one of the following helps experimental confirmation of the Crystalline state of matter?
17
The electrical conductivity of pure semiconductor is:
18
Consider the following statements pertaining to the resistance of a conductor:
1. Resistance can be simply defined as the ratio of voltage across the conductor to the current through the conductor. This is, in fact, Georg Ohm’s law.
2. Resistance is a function of voltage and current.
3. Resistance is a function of conductor geometry and its conductivity
Which of the above statements are correct?
1. Resistance can be simply defined as the ratio of voltage across the conductor to the current through the conductor. This is, in fact, Georg Ohm’s law.
2. Resistance is a function of voltage and current.
3. Resistance is a function of conductor geometry and its conductivity
Which of the above statements are correct?
19
The ratio of ionic radii of Cations i.e.and that of Anions i.e.for stable and unstable ceramic crystal structure, is:
20
Which one of the following statements is correct?
21
In an extrinsic semiconductor the conductivity significantly depends upon:
22
In some substances when an electric field is applied the substance become polarized. The electrons and nucleii assume new geometrical positions and the mechanical dimensions are altered. This phenomenon is called:
23
In ferromagnetic materials, the net magnetic moment created due to magnetization by an applied field as:
24
At what temperatures domains lose their ferromagnetic properties?
25
Which of the following materials does not have paramagnetic properties?
1. Rare earth elements (with incomplete shell)
2. Transition elements
3. Magnesium oxide
Select the correct answer from the codes given below:
1. Rare earth elements (with incomplete shell)
2. Transition elements
3. Magnesium oxide
Select the correct answer from the codes given below:
26
In a superconducting magnet, wires of superconducting material are embedded in the thick copper matrix, because while the material is in the superconducting state:
27
The crystal structure of some Ceramic materials may be thought of being composed of electrically charged Cations and Anions, instead of Atoms, and as such:
28
Manganin alloy used for making resistors for laboratory instruments contains:
29
A rolled-paper capacitor of value 0.02 is to be constructed using two strips of aluminiumof width 6 cm, and wax impregnated paper of thickness 0.06 mm whose relative permittivity is 3. The length of foil strips should be:
30
In a semiconductor diode, cut-in voltage is the voltage:
Farm Machinery And Power
1
A fin will be more effective when Bio number is
2
A tank of length, breadth and height in the ratio of 2:1:2 is full of water. The ratio of hydrostatic force at the bottom to that at any larger vertical surface is
3
Which of the following fluids exhibit a certain shear stress at zero shear strain rate followed by a straight line relationship between shear stress and shear strain rate?
4
What is the specific gravity of a marble stone, which weighs 400N in air, and 200N in water? (g=10m/s2)
5
What is the intensity of pressure in the following SI units, when specific gravity of mercury is 13.6 and the intensity of pressure is 400KPa ?
6
Consider the following statements:
1.If a small upward displacement is given to a floating body, it results in the reduction of the buoyant force acting on the body
2.A slight horizontal displacement does not change either the magnitude or the location of the buoyant force
Which of the above statements is/are correct?
1.If a small upward displacement is given to a floating body, it results in the reduction of the buoyant force acting on the body
2.A slight horizontal displacement does not change either the magnitude or the location of the buoyant force
Which of the above statements is/are correct?
7
State whether following flow field is physically possible?
8
In a differential manometer, a head of 0.5 m of fluid A in limb 1 is found to balance a head of 0.3 m of fluid B in limb 2. The atmospheric pressure is 760 mm of mercury. The ratio of specific gravities of A to B is
9
A Reversed Carnot Engine removes 50 kW from a heat sink. The temperature of the heat sink is 250 K and the temperature of the heat reservoir is 300 K. The power required of the engine is
10
On which of the following just in time manufacturing philosophy emphasizes ?
11
In a stream line steady flow, two points A and B on a stream line are 1m apart and the flow velocity varies uniformly from 2m/s to 5m/s. What is the acceleration of fluid at B?
12
The stream function is given by Ψ = 3xy, then the velocity at the point (2,3) is
13
The boundary layer thickness at a given distance from the leading edge of a flat plate is
14
In a laminar flow through a circular pipe, the discharge varies
15
A fluid is flowing over a flat plate. At distance of 8 cm from the leading edge, the Reynolds number is found to be 25600. The thickness of the boundary layer at this point is
16
Air is flowing over a flat plate with a free stream velocity of 24 m/s, and its kinematic viscosity is 72 ×10-6m2/s. If at a particular point, the Reynolds number is 30000, its location from the leading edge is
17
In a refrigerator, the evaporator and condenser coil temperatures are –33°C and 27°C, respectively. Assuming that the maximum COP is realized, the required power input for a refrigerating effect of 4 kW is
18
In a hydraulic coupling
19
Consider the following statements:
1.The wheel can be operated freely in air
2.Pressure at the exit of the nozzle is atmospheric
3.Pressure does not vary along the moving vanes
4.Change the direction of momentum imparts thrust over moving vanes Which of the following statements are applied to impulse turbine?
1.The wheel can be operated freely in air
2.Pressure at the exit of the nozzle is atmospheric
3.Pressure does not vary along the moving vanes
4.Change the direction of momentum imparts thrust over moving vanes Which of the following statements are applied to impulse turbine?
20
A water jet 0.0015m2in area issues from a nozzle with 15 m/s velocity. It is made to impinge perpendicular on to a plate that moves away from the jet with a velocity of 5 m/s. The force on the plate due to this impact is
21
Consider the following statements with regard to hydraulic turbines:
1.Kaplan turbines are most efficient at part load operations.
2.If n is the number of jets in a Pelton turbine, then the specific speed is proportional to n2.
3.The flow ratio of Francis turbines are in the range of 0.1 – 0.3.
Which of the above statements is/are correct?
1.Kaplan turbines are most efficient at part load operations.
2.If n is the number of jets in a Pelton turbine, then the specific speed is proportional to n2.
3.The flow ratio of Francis turbines are in the range of 0.1 – 0.3.
Which of the above statements is/are correct?
22
Which of the following is a Vector quantity ?
23
Bernoulli’s equation is applicable between any two points located in
24
Water flows through a smooth circular pipe of diameter D and length L because of a pressure difference ΔP across the length. The volume flow rate is Q and the flow is turbulent with Reynolds number 105. If the pressure difference is increased to 4ΔP the volume flow rate will be
25
Heat is lost from a 100 mm diameter steam pipe placed horizontally in ambient air at 30°C. If the Nusselt number is 25 and the thermal conductivity of the air is 0.03 W/m K, then the heat transfer coefficient will be
26
For laminar flow through a round pipe, the shear stress
27
Percentage clongation during tensile test is indicative of
28
Which of the above statements is not correct in the context of laminar flow through a pipeline?
29
Laminar flow between closely spaced parallel plates is governed by the consideration of which one of the following pair of forces?
30
Formation and collapse of vapour bubbles are believed to be the root cause for cavitation in hydraulic turbines. Most favorable condition for the formation of bubbles is set in the turbine at
31
For fully developed laminar flow through a circular pipe with Reynolds number Rethe friction factor is
32
The ratio of power outlet of the pump to the power input to the pump is known as
33
A pump is defined as a device which converts
34
The specific speed of a pump is defined as the speed of the unit of such a size that is
35
Negative slip occurs in reciprocating pumps, when delivery pipe is
36
The pressure inside a soap bubble of 50 mm diameter is 25 N/m2 above the atmospheric pressure. The surface tension in soap film would be
37
A Newtonian fluid is one which
38
Unlike the viscosity of fluids, the viscosity of gases increases with increasing temperature. This is due to
39
Manometer is a device used for measuring
40
When a dolphin glides through air, it experiences an external pressure of 0.75 m of mercury. The absolute pressure on dolphin when it is 5m below the free surface of the water is
41
Which of the above statements is correct?
42
A wall of 0.6m thickness has normal area of 1.5 m2 and is made up of material of thermal conductivity 0.4 W/mK. If the temperature on the two sides of the wall are 800°C and 1000°C, the thermal resistance of the wall is
43
A flownet is a graphical representation of streamlines and euqipotnetial lines such as these lines
44
Which of the above statements is correct for the velocity of potential?
45
Angle of diverging portion of the venturimeter is limited to 7°, because:
1.Flow decelerates in the diverging portion and pressure increases in the downstream direction. Hence, the fluid experience an adverse pressure gradient, if the divergence angle is large.
2 .Flow separation takes place due to adverse pressure gradient when divergence angle is large.
3 .If the divergence angle is large, a negative pressure is created at the throat which obstructs the flow of fluid.
Which of the above reasons are correct?
1.Flow decelerates in the diverging portion and pressure increases in the downstream direction. Hence, the fluid experience an adverse pressure gradient, if the divergence angle is large.
2 .Flow separation takes place due to adverse pressure gradient when divergence angle is large.
3 .If the divergence angle is large, a negative pressure is created at the throat which obstructs the flow of fluid.
Which of the above reasons are correct?
46
A gas is flowing through an insulated nozzle. If the inlet velocity of gas is negligible and there is an enthalpy drop of 45kJ/kg, the velocity of gas leaving the nozzle is
47
Which of the above statements are correct for turbo-prop powered aircrafts?
1 .The propulsion efficiency of turbo-prop is higher than that of turbo-jet and rockets for low speeds up to about 800km/hr.
2.For the same thrust the turbine in the turbo prop aircraft is smaller than in the turbo-jet aircraft.
3.For the turbo-prop the flight velocity cannot exceed the jet velocity.
1 .The propulsion efficiency of turbo-prop is higher than that of turbo-jet and rockets for low speeds up to about 800km/hr.
2.For the same thrust the turbine in the turbo prop aircraft is smaller than in the turbo-jet aircraft.
3.For the turbo-prop the flight velocity cannot exceed the jet velocity.
48
If absolute jet exit velocity from a jet engine is 2800m/s and forward flight velocity is 1400m/s then propulsive efficiency is
49
An air-breathing aircraft is flying at an altitude where the air density is half the value at ground level. With reference to the ground level, the air fuel ratio at this altitude will be
50
Which of the above statements are correct for rockets?
1.Unlike the turbo-jet aircraft, in rockets the flight velocity can exceed the jet velocity.
2.In rockets gases having lower molecular weight increase the specific thrust.
3.In rockets the gases are expanded in the nozzle up to the atmospheric pressure.
1.Unlike the turbo-jet aircraft, in rockets the flight velocity can exceed the jet velocity.
2.In rockets gases having lower molecular weight increase the specific thrust.
3.In rockets the gases are expanded in the nozzle up to the atmospheric pressure.
51
In a differential manometer a head of 0.6m of fluid A in limb 1 is found to balance a head of 0.3m of fluid B in limb 2. The ratio of specific gravities of A to B is
52
At x = 0, the function f (x) = |x| will be
53
The center of pressure of a plane submerged surface
54
A furnace is provided with an insulating refractory lining. The overall thermal conductivity of the material is 0.03 W/mK. The thickness of the lining is 100 mm. The inner and outer temperatures are 250°C and 50°C, respectively. The heat loss to the surroundings will be
55
A piece of metal of specific gravity 7 floats in mercury of specific gravity 13.6, what fraction of its volume is under mercury?
56
A right circular cylinder, open at the top, is filled with a liquid of specific gravity 1.2, and rotated about its vertical axis at such a speed that half of the liquid spills out. The pressure at the center of the bottom is
57
Consider the following statements about velocity potential:
1.Velocity potential is a vector function similar to stream function
2.It is a fully three dimensional function and not limited to two
coordinates
3.Velocity potential does not exist at stagnation points
4.Velocity potential exists only if the flow is irrotational
Which of the above statements are correct?
1.Velocity potential is a vector function similar to stream function
2.It is a fully three dimensional function and not limited to two
coordinates
3.Velocity potential does not exist at stagnation points
4.Velocity potential exists only if the flow is irrotational
Which of the above statements are correct?
58
During a constant pressure expansion of a gas, 33.3% heat is converted into work while the temperature rises by 20 K. The specific heat of the gas at constant pressure as a proportion of work, W is
59
Principle mechanism of material removal in ECM?
60
The centre-line velocity in a pipe flow is 2m/s. What is the average flow velocity in the pipe if the Reynolds number of the flow is 800?
61
In flow through a pipe, the transition from laminar to turbulent flow does not depend on
62
A 0.20m diameter pipe 20m long transports oil at a flow rate of0.01m3/s. Calculate power required to maintain flow if dynamic viscosity and density of oil is 0.08 Pas and 900 kg/m3 respectively
63
Pressure loss for laminar flow through pipeline is dependent
64
Fanno line is a flow in a constant area duct
65
In an adiabatic flow with friction through a constant area duct, the following phenomenon are predicted:
1.The flow downstream tends to be sonic irrespective of the Mach-number upstream
2.In the case of initially supersonic flow, any increase in duct length beyond choked flow would make the exit flow subsonic
3.In the case of initially subsonic flow, any increase in duct length will not change sonic flow at the exit
4.The optimum pipe length for sonic outlet in supersonic flow is considerably longer than that of subsonic flow for the same flow rate
Which of these are correct?
1.The flow downstream tends to be sonic irrespective of the Mach-number upstream
2.In the case of initially supersonic flow, any increase in duct length beyond choked flow would make the exit flow subsonic
3.In the case of initially subsonic flow, any increase in duct length will not change sonic flow at the exit
4.The optimum pipe length for sonic outlet in supersonic flow is considerably longer than that of subsonic flow for the same flow rate
Which of these are correct?
66
In a reciprocating pump, air vessels are used to
67
Consider the following statements pertaining to centrifugal pumps:
1.The inlet to the impeller of a centrifugal pump is always axial, while the outlet may be radial or inclined.
2.The impeller may be shrouded on both sides with an eye at the centre and vanes curved backwards.
3.Impeller of double entry type has a balanced radial thrust.
4.Un-shrouded and part shrouded impeller are used only where high efficiency is unimportant.
Which of these statements are correct?
1.The inlet to the impeller of a centrifugal pump is always axial, while the outlet may be radial or inclined.
2.The impeller may be shrouded on both sides with an eye at the centre and vanes curved backwards.
3.Impeller of double entry type has a balanced radial thrust.
4.Un-shrouded and part shrouded impeller are used only where high efficiency is unimportant.
Which of these statements are correct?
68
A centrifugal pump is fully primed, but on starting it fails to deliver fluid. Thr probable reasons are listed below:
1.Leaky foot valve or suction line
2.Suction head is very slow
3.Insufficient motor speed
4.Damaged or closed delivery valve
Which of these reasons are correct?
1.Leaky foot valve or suction line
2.Suction head is very slow
3.Insufficient motor speed
4.Damaged or closed delivery valve
Which of these reasons are correct?
69
A centrifugal pump is to discharge 0.118 m3/s at speed of 1450 rpm against a head of 25m. The impeller diameter is 25cm, its width at outlet is 5cm and manometric efficiency is 75%. The vane angle at outer periphery of impeller is
70
A turbine is working under a head of 200m. The power developed by the turbine is 100kW and discharge through the turbine is 0.125 m3/s. In such case, the ratio of unit power to unit discharge for the turbine will be