McqMate
These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Mechanical Engineering .
| 1. |
Nozzle is used to control direction or characteristics of flow. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: nozzle is used to control the direction and characteristics of flow. | |
| 2. |
In fountains the type of nozzle used is |
| A. | none of the mentioned |
| B. | turbulent jet |
| C. | high speed nozzle |
| D. | laminar jet |
| Answer» D. laminar jet | |
| Explanation: laminar jet nozzle is used to convert the fluid in laminar flow. | |
| 3. |
If mach number is less than one then its flow is |
| A. | subsonic flow |
| B. | turbulent flow |
| C. | laminar flow |
| D. | none of the mentioned |
| Answer» A. subsonic flow | |
| Explanation: if m<1 then it is subsonic flow. | |
| 4. |
The steam leaves the nozzle at a |
| A. | low pressure and a high velocity |
| B. | high pressure and a high velocity |
| C. | high pressure and a low velocity |
| D. | low pressure and a low velocity |
| Answer» A. low pressure and a high velocity | |
| Explanation: the steam leaves the nozzle at low pressure & a high velocity as the action of steam is best suited for turbine operations under these conditions. | |
| 5. |
When mach number is greater than one the flow is |
| A. | subsonic |
| B. | supersonic |
| C. | laminar |
| D. | none of the mentioned |
| Answer» B. supersonic | |
| Explanation: when m>1 the flow is supersonic. | |
| 6. |
In rocket engines the amount of expansion in Nozzle determines the |
| A. | exit temperature |
| B. | exit pressure |
| C. | exit temperature & pressure |
| D. | none of the mentioned |
| Answer» C. exit temperature & pressure | |
| Explanation: when the flow is subsonic, air in nozzle expands isoentropically and hence exit temperature and exit pressure depends on the amount of expansion. | |
| 7. |
De-Laval turbine is a |
| A. | multi rotor impulse turbine |
| B. | impulse reaction turbine |
| C. | single rotor impulse turbine |
| D. | none of the mentioned |
| Answer» C. single rotor impulse turbine | |
| Explanation: a de-laval turbine is a single rotor impulse turbine. | |
| 8. |
The Parsons’ reaction turbine has |
| A. | only moving blades |
| B. | only fixed blades |
| C. | fixed and moving blades of different shape |
| D. | identical fixed and moving blades |
| Answer» D. identical fixed and moving blades | |
| Explanation: the parsons’ reaction turbine has identical fixed & moving blades. | |
| 9. |
What is the critical pressure ratio for initially wet steam? |
| A. | 0.582 |
| B. | 0.546 |
| C. | 0.577 |
| D. | 0.601 |
| Answer» A. 0.582 | |
| Explanation: the critical pressure ratio for initially wet steam is 0.582. | |
| 10. |
The ratio of the useful heat drop to the isentropic heat drop is called |
| A. | condenser efficiency |
| B. | nozzle efficiency |
| C. | vacuum efficiency |
| D. | boiler efficiency |
| Answer» B. nozzle efficiency | |
| Explanation: the ratio of the useful heat drop to the isentropic heat drop is called nozzle efficiency. | |
| 11. |
Rateau turbine is |
| A. | pressure-velocity compounded turbine |
| B. | simple reaction turbine |
| C. | velocity compounded turbine |
| D. | pressure compounded turbine |
| Answer» D. pressure compounded turbine | |
| Explanation: a rateau turbine is a pressure compounded turbine. | |
| 12. |
When the cross-section of a nozzle increases continuously from entrance to exit, it is called a |
| A. | convergent-divergent nozzle |
| B. | divergent nozzle |
| C. | convergent nozzle |
| D. | none of the mentioned |
| Answer» B. divergent nozzle | |
| Explanation: when the cross-section of a nozzle increases continuously from entrance to exit, it is called a divergent nozzle. | |
| 13. |
Aeroderivative engines have pressure ratios |
| A. | greater than 30 |
| B. | lesser than 30 and greater than 20 |
| C. | greater than 50 |
| D. | none of the mentioned |
| Answer» A. greater than 30 | |
| Explanation: higher pressure ratios of greater than 30 are used in aeroderivative engines. | |
| 14. |
Aeroderivative engines are larger. |
| A. | true |
| B. | false |
| Answer» B. false | |
| Explanation: aeroderivative engines are compact and smaller in size. | |
| 15. |
Aeroderivative engines release higher emissions. |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: aeroderivative engines are smaller and produce high output as a result of which they release higher emissions. | |
| 16. |
Critical pressure ratio is ratios of pressures at discharge. |
| A. | minimum |
| B. | none of the mentioned |
| C. | optimum |
| D. | maximum |
| Answer» D. maximum | |
| Explanation: critical pressure ratio is the ratios of pressure at maximum discharge. | |
| 17. |
Ratio of critical pressure to inlet pressure in known as |
| A. | none of the mentioned |
| B. | pressure ratio |
| C. | critical pressure ratio |
| D. | isoentropic pressure ratio |
| Answer» C. critical pressure ratio | |
| Explanation: ratio of critical pressure to inlet pressure is called as critical pressure ratio. | |
| 18. |
In De Laval Nozzle critical pressure ratio is given by (2/y+1)^(y/y-1). |
| A. | true |
| B. | false |
| Answer» A. true | |
| Explanation: critical pressure ratio of de laval nozzle is derived theoretically. | |
| 19. |
With the increase in pressure, the exit velocity |
| A. | decreases |
| B. | increases |
| C. | same |
| D. | independent |
| Answer» A. decreases | |
| Explanation: pressure is inversely proportional to the velocity. so, with the increase in pressure, the exit velocity decreases. we know that the pressure is equal to force per unit area, this contradicts the above statement. | |
| 20. |
The Prandtl Number approximates |
| A. | momentum diffusivity to thermal diffusivity |
| B. | thermal diffusivity to momentum diffusivity |
| C. | shear stress to thermal diffusivity |
| D. | thermal diffusivity to kinematic viscosity |
| Answer» A. momentum diffusivity to thermal diffusivity | |
| Explanation: the prandtl number is a dimensionless number. it approximates the ratio of momentum diffusivity to thermal diffusivity. it can be expressed as pr = v/ α(1). where α= thermal diffusivity and v= momentum diffusivity. | |
| 21. |
Pumps increase |
| A. | pressure |
| B. | velocity |
| C. | momentum |
| D. | heat |
| Answer» A. pressure | |
| Explanation: pumps increase pressure rather than velocity. during the pumping process, a housing is provided for the pumping elements. these parts can change the speed. pumps create a passage way that will squirt the fluid passing through it. thus, pumping increases pressure. | |
| 22. |
Which among the following is the formula for volumetric flow rate? |
| A. | q = v/a |
| B. | q = av |
| C. | q = a+v |
| D. | q = a-v |
| Answer» B. q = av | |
| Explanation: volumetric flow rate is given by q= a.v. where v is the flow velocity of the fluid, and a is the area of cross section of the surface. area of a surface is also called as the vector area. thus, the right answer is q = av. | |
| 23. |
Which among the following is the formula for mass flow rate? |
| A. | q = m/p |
| B. | q = mp |
| C. | q = m + p |
| D. | q = m – p |
| Answer» B. q = mp | |
| Explanation: mass flow rate is given by q=m/p. this is a relation expressed for mass flow rate. when ‘m’ is the mass flow rate. | |
| 24. |
Compressible flow mainly deals with |
| A. | solid dynamics |
| B. | liquid dynamics |
| C. | gas dynamics |
| D. | solid and liquid dynamics |
| Answer» C. gas dynamics | |
| Explanation: compressible flow is a branch of fluid mechanics that deals with different | |
| 25. |
Which among the following is an assumption of the compressible flow? |
| A. | resistance to flow of object |
| B. | no-slip condition |
| C. | known mass flow rate |
| D. | resistance to flow of heat |
| Answer» B. no-slip condition | |
| Explanation: the related assumption of a compressible fluid flow is no-slip condition. it is assumed that the flow velocity at the solid surface is equal to the velocity of the surface itself. it is in direct consequence with the continuum flow. | |
| 26. |
What is Mach number? |
| A. | speed of object * speed of sound |
| B. | speed of object /speed of sound |
| C. | speed of object + speed of sound |
| D. | speed of object- speed of sound |
| Answer» B. speed of object /speed of sound | |
| Explanation: mach number is defined as the ratio of the speed of an object to the speed of sound. mach number is denoted by ‘m’. | |
| 27. |
Which of the following kinetic friction is smaller? |
| A. | limiting friction |
| B. | static friction |
| C. | rolling friction |
| D. | sliding friction |
| Answer» C. rolling friction | |
| Explanation: the force which comes into play when a body rolls over the surface of another body is called rolling friction. for the same magnitude of a normal reaction, rolling friction is always greater than the sliding friction. | |
| 28. |
A mass of 4kg rests on a horizontal plane. The plane is gradually inclined until at an angle θ= 15° with the horizontal, the mass just begins to slide. What is the coefficient of static friction between the block and the surface? |
| A. | 0.814 |
| B. | 0.27 |
| C. | 1.5 |
| D. | 3.5 |
| Answer» B. 0.27 | |
| Explanation: θ = 15° is the angle of response. | |
| 29. |
A scooter weighs 120kg f. Brakes are applied so that wheels stop rolling and start skidding. Find the force of friction if the coefficient of friction is 0.4. |
| A. | 60kg f |
| B. | 48kg f |
| C. | 25kg f |
| D. | 32kg f |
| Answer» B. 48kg f | |
| Explanation: weight of the scooter = 120kg f μ = 0.4 | |
| 30. |
How is friction due to air reduced? |
| A. | streamlining |
| B. | lubrication |
| C. | by using ball bearings |
| D. | by polishing |
| Answer» A. streamlining | |
| Explanation: friction due to air is considerably reduced by streamlining the shape pf the body moving through air. for example, jets have a streamline shape. | |
| 31. |
Friction can be increased by |
| A. | using air cushion |
| B. | lubricants |
| C. | using sand |
| D. | using ball bearings |
| Answer» C. using sand | |
| Explanation: by throwing sand the force of friction between the wheels and the track becomes easier. on rainy days, we throw sand on the slippery ground. this increases the friction between our feet and the ground and reduces the chance of slipping. | |
| 32. |
When moving along a curved path, he |
| A. | leans inwards |
| B. | leans outwards |
| C. | is still |
| D. | leans sideways |
| Answer» A. leans inwards | |
| Explanation: when a cyclist goes around a curved path, a centripetal force is required. the force between the tyres and the road is small to provide the necessary centripetal force. that is why a cyclist going around a curve leans inwards because the horizontal component of the normal reaction provides the necessary centripetal force. | |
| 33. |
A train has to negotiate a curve of radius 400m. By how much should the putter rail be raised with respect to inner rail for speed of 48 km/h? The distance between the rails is 1m. |
| A. | 0.20m |
| B. | 0.0454m |
| C. | 0.45m |
| D. | 0.020m |
| Answer» B. 0.0454m | |
| Explanation: h = (v2 l)/rg h = 402/32 = 0.0454m. | |
| 34. |
When a gas is pushed through a pipe, the gaseous molecules are by the pipe’s walls |
| A. | attracted |
| B. | absorbed |
| C. | deflected |
| D. | dissipated |
| Answer» C. deflected | |
| Explanation: this is because there is no attractive force present in the tube for the process of attraction to occur. also, the surface of pipes is not an absorbing one, hence absorption is also ruled out. a pipe is | |
| 35. |
In fluid dynamics, the velocity of the fluid in the stagnation point is |
| A. | zero |
| B. | infinite |
| C. | non-existent |
| D. | negative |
| Answer» A. zero | |
| Explanation: stagnant point is a point where there is no movement of the fluid. when there is no movement, the velocity will be 0. hence the answer is 0. | |
| 36. |
If the speed of sound is much than that of the gas, the gas density will stay constant. |
| A. | smaller |
| B. | larger |
| C. | equal to |
| D. | non-existent |
| Answer» B. larger | |
| Explanation: this is because only with speed of sound is larger, it’ll be able to compensate for the speed of gas. under such situations, | |
| 37. |
Isentropic nozzle flow states about the movement of a gas or fluid through a narrow orifice without an increase or decrease in |
| A. | accelerating |
| B. | decelerating |
| C. | equilibrium |
| D. | exponential increase |
| Answer» B. decelerating | |
| Explanation: initially the flow has a velocity. in the stagnant state, the velocity is 0. for this to happen, there should be a deceleration of the velocity. hence, deceleration is the answer. | |
| 38. |
To refrain from separation in subsonic nozzles, the expansion angle must not be more than |
| A. | 10 degrees |
| B. | 20 degrees |
| C. | 30 degrees |
| D. | 40 degrees |
| Answer» A. 10 degrees | |
| Explanation: if the angle is more than 10 degrees, there will be a drift amidst the nozzle. at any angle more than 10 degrees, this separation will occur. but the minimum value is 10 degrees. so, the answer is 10 degrees. | |
| 39. |
Gas flows through the nozzle from an area of pressure (called the chamber) to one of pressure |
| A. | high, low |
| B. | low, high |
| C. | same, same |
| D. | constant, infinite |
| Answer» A. high, low | |
| Explanation: anything that flows or runs moves from a region of higher value to lower value. we can take the example of any physical parameter like pressure, altitude etc. | |
| 40. |
Converging-diverging nozzle is also known as |
| A. | pascal nozzle |
| B. | bernouille’s nozzle |
| C. | toricelli’s nozzle |
| D. | de laval’ nozzle |
| Answer» D. de laval’ nozzle | |
| Explanation: this is because this nozzle was invented by carl de laval. so, it is also named after him. hence de-laval nozzle is the option. | |
| 41. |
When the pressure chamber is big, the flow velocities are |
| A. | large |
| B. | negligible |
| C. | constant |
| D. | increasing |
| Answer» B. negligible | |
| Explanation: when the chamber is large, the area is high. velocity is inversely proportional | |
| 42. |
For a compressible, ideal gas, mass flow rate depends on parameters such as flow area, pressure, temperature, properties of the gas, and |
| A. | avogardo’s number |
| B. | mach number |
| C. | reynold’s number |
| D. | le-grange’ number |
| Answer» B. mach number | |
| Explanation: mass flow rate should depend on the velocity. here mach number denotes the velocity. so, the mach number gives the right answer. | |
| 43. |
Which type of boilers use orifice to control the flow circulation? |
| A. | natural circulation boilers |
| B. | forced convection boilers |
| C. | once-through boilers |
| D. | positive forced circulation boilers |
| Answer» B. forced convection boilers | |
| Explanation: in these boilers water is circulated by using an additional pump. these boilers often use orifices to control the flow circulation. orifices are located at the bottom of the tubes that ensure even distribution of flow through water wall tubes. these boilers can generate steam upto about 200 bar. | |
| 44. |
What is the advantage of having smaller ratio of water to steam space? |
| A. | steam can be generated at a faster even if the boiler is cold |
| B. | increases the rate of evaporation |
| C. | water is made cyclic, i.e., from boiler drum to water tube and back to drum |
| D. | helps in mobilizing the boiler |
| Answer» A. steam can be generated at a faster even if the boiler is cold | |
| Explanation: rate of evaporation is more as area of heating surface is more due to presence of large small diameter tubes. due to that smaller water ratio is allowed to steam space where in the steam can be generated as a faster rate even if the boiler is cold. as the rate of evaporation is more, it is preferred in steam power plants for power generation. | |
| 45. |
Which are the major types of boilers that are operated in world today? |
| A. | natural circulation boiler |
| B. | forced circulation boiler |
| C. | fire tube boiler |
| D. | once through boiler |
| Answer» D. once through boiler | |
| Explanation: the once through boiler has higher load response characteristics due to the fact that it does not have drum and has much lower water inventory. many times load change response is dictated by the firing system and its controls rather than the boiler, per-say. | |
| 46. |
How many level indicators are there in the water level indicator of a boiler? |
| A. | 1 |
| B. | 2 |
| C. | 3 |
| D. | 4 |
| Answer» B. 2 | |
| Explanation: the function of the water level indicator is to indicate the level of water | |
| 47. |
What is the function of pressure gauge in the boiler? |
| A. | to indicate steam pressure |
| B. | to indicate water pressure |
| C. | to indicate air pressure |
| D. | to indicate flue gas pressure |
| Answer» A. to indicate steam pressure | |
| Explanation: the function of the pressure gauge is to indicate the steam pressure inside the boiler drum in bar or in kgf in cm2 or in kn/m2 in gauge pressure. if the boiler is fitted with a superheater, one more pressure gauge fitted to the superheater header indicates the superheated steam pressure at any given instant. | |
| 48. |
other than Steam stop valve in the boiler which is the other similar type of valve used? |
| A. | non-reversible valve |
| B. | transient valve |
| C. | reversible valve |
| D. | junction valve |
| Answer» D. junction valve | |
| Explanation: stop valve and junction valve are essentially same. conventionally stop valves are smaller in size whereas, junction valves are larger. when the valve is mounted on the top most portion of the steam drum, normally the valve is called junction valve. if it is connected in the steam pipe to regulate the flow of steam, the valve is known as stop valve. | |
| 49. |
What is the function of Blow down valve of a boiler? |
| A. | to remove sludge |
| B. | to build sediments |
| C. | to remove flue gas |
| D. | to remove ash |
| Answer» A. to remove sludge | |
| Explanation: blow down valve is also called as blow-off-cock. the function of this valve | |
| 50. |
What is the function of fusible plug in the boiler? |
| A. | protect the fire tube |
| B. | to trip on overload |
| C. | to act as a junction switch |
| D. | to maintain pressure |
| Answer» A. protect the fire tube | |
| Explanation: the function of the fusible plug is to protect the fire tube from burning due to excessive heating. this usually happens when the water level inside the drum becomes too low and the shell and crown plate are directly exposed to steam space. | |
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