Quiz: Mechanical Engineering 31st May

Quiz: Mechanical Engineering
Exam: AE/JE
Topic: Miscellaneous

Each question carries 2 mark
Negative marking: 1/3 mark
Time: 15 Minutes

Q1. Consider the following characteristics:
1. The fluid enters the pump axially and is discharged radially
2. Maximum efficiency may be of the order of 90%
3. Development of low head
4. A limited suction capacity
Which of the following characteristics are possessed by axial flow pumps?
(a) 1 and 2
(b) 2 and 3
(c) 2 and 4
(d) 3 and 4

Q2. Consider the following statements with regards to the specific speeds of different types of turbines:
1. High specific speed implies that it is a pelton wheel.
2, Medium specific speed implies that it is an axial flow turbine.
3. Low specific speed implies that it is a francis turbine.
Which of these statements given above is/are correct?
(a) 1 only
(b) 2 only
(c) 3 only
(d) None

Q3. Which one of the following information cannot be obtained from the static tensile test of a mild steel specimen?
(a) Modulus of elasticity
(b) Qualitative determination of toughness
(c) Ductility
(d) Weldability

Q4. Powder metallurgy process involves which of the following?
1. Converting metals such as iron etc. into powder form.
2. Blending powders of metals then compacting and compressing to desired shape at room temp.
3. Heating and compressed articles to a temp. Above melting point of metal.
Select the correct answer from below
(a) 1, 2 and 3
(b) 1 and 2 only
(c) 2 and 3 only
(d) 1 and 3 only

Q5. The path and movement followed by men, material and equipment’s in executing the activities is indicated by which of the following?
(a) Flow diagram
(b) String diagram
(c) Travel charts
(d) Man-Machine charts

Q6. A graphical representation of the coordinated activities (fundamental motions) of an operator’s body members, on a common time scale is known as
(a) SIMO chart
(b) Man-machine chart
(c) Two handed process chart
(d) Gantt chart

Q7. Dispatching function of production planning and control refers to
(a) dispatch of finished goods on order
(b) movement of in process material from shop to shop
(c) authorizing a production work order to be launched
(d) dispatch of bills and invoices to the customer

Q8. The mixing of two or more streams of moist air in air conditioning process is
(a) an isothermal process
(b) an adiabatic process
(c) a constant pressure process
(d) a general polytropic process

Q9. In most of water coolers, the atmospheric air is made to pass through a wet khas-khas or bamboo mat to render a surface cool in summer. Thermodynamically, this process may be called
(a) Sensible cooling
(b) Cooling and dehumidification
(c) Cooling and humidification
(d) Adiabatic saturation

Q10. Consider the following statements:
In a chemical dehumidification process,
1. DPT decreases
2. WBT decreases
3. DBT decreases
Which of these are correct?
(a) 1, 2 and 3
(b) 1 and 2
(c) 1 and 3
(d) 2 and 3

Solutions

S1. Ans.(b)
Sol. An axial flow pump is one in which the fluid enters parallel to the axis of rotation and leaves in axially tangential plane.
It is used for high discharge and low head.
So statement 1 and 4 are wrong

S2. Ans.(d)
Sol. Pelton wheel has low specific speed.
Medium specific speed implies that it is a reaction turbine (radial flow), generally francis turbine.
Francis turbine has medium specific speed.
All statements are wrong.

S3. Ans.(b)
Sol. Energy required to fracture a notched specimen is measured in izod impact toughness test and charpy impact toughness test where measured energy is indicative of relative toughness of the material.

S4. Ans.(b)
Sol. Sintering is a heat treatment process applied to compacted powder in order to impart strength to the product. It is carried at temperature below the melting point of metal.

S5. Ans.(a)
Sol. Flow diagram shows the location and sequence of all activities, which are carried by workers. It also shows the route, followed by material, components or subassemblies.

S6. Ans.(a)
Sol. SIMO chart is based on film analysis used to record therbligs or a group of therbligs performed by different body members of one or more workers simultaneously on a common time scale.
Two handed process chart is a chart in which the activities of a workers hand are recorded in their relationship to each other.

S7. Ans.(c)
Sol. Dispatching function of production, planning and control refers to authorizing a production work to be launched.

S8. Ans (b)
Sol.

The mixing of two or more streams of moist air in air conditioning process is an adiabatic process. Depending upon the state of the individual streams, the mixing process can take place with or without condensation of moisture.

In the given figure, adiabatic mixing without condensation of two streams at states 1 and 2 is shown by 1-3-2 and adiabatic mixing with condensation at states 1^’ and 2^’ is shown by 1’-3’-2’.

S9. Ans (d)
Sol. Most of the water cooler work on the principle of adiabatic saturation. Evaporative humidification processes normally occur without external heat transfer and are therefore adiabatic.
In adiabatic saturation or evaporative cooling, we get cooling of the air as sensible heat is used as latent heat of vaporization to vaporize the moisture at khas-khas surface. This moisture is removed by moving air. This transfer of moisture takes place due to differences in vapor pressures of khas-khas and dry-air. The vapor pressure depends upon moisture content and temperature of the cooling surface.

S10. Ans (b)
Sol. chemical dehumidification process can be achieved by using a hygroscopic material, which absorbs or adsorbs the water vapor from the moisture. If the process is taking place in an isothermally insulated container then enthalpy of the air remains constant. So, when the moisture is absorbed from the air by the hygroscopic material, then its temperature increases as heat of condensation released by the condensate absorbed by the hygroscopic material.
Due to chemical dehumidification process DBT ↑, WBT ↓ and DPT ↓.

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