Manufacturing Technology I Set 4

Mechanical Engineering

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This set of Manufacturing Technology 1 Multiple Choice Questions & Answers (MCQs) focuses on Manufacturing Technology I Set 4

Q1 | The direction of rmf when a single phase supply is given to stator of three phase induction motor is?
  • zero
  • ns
  • 2ns
  • -ns
Answer: zero
Explaination:
there will be no rmf generated as a single phase is only fed to the three phase of induction motor.
Q2 | The direction of rmf when a three phase supply is given to stator of three phase induction motor is?
  • zero
  • ns
  • 2ns
  • -ns
Answer: ns
Explaination:
there will be rotating magnetic field will be produced causing the emf to be induced and the current will flow in the rotor at a speed of synchronous speed.
Q3 | Two three phase induction motors A and B are identical in all respects except that motor A has a larger air-gap than motor B. Which motor will have more no load current?
  • a
  • b
  • both a and b
  • neither a nor b
Answer: a
Explaination:
as the air gap of motor a is more, it will require more flux to excitation and so the no load current.
Q4 | Two three phase induction motors A and B are identical in all respects except that motor A has a larger air-gap than motor B. Which motor will have poorer power factor?
  • a
  • b
  • both a and b
  • neither a nor b
Answer: a
Explaination:
due to larger air gap of motor a, it will need more of exciting current. so the no load angle will increase and power factor will deteriorate.
Q5 | Two three phase induction motors A and B are identical in all respects except that motor A has a larger air-gap than motor B. Which motor will have better full-load power factor?
  • a
  • b
  • both a and b
  • neither a nor b
Answer: b
Explaination:
at full load conditions, the excitation current is not very high and so the power factor improves.
Q6 | A three phase induction motor is sometimes calles a generalized transformer in so far as voltage and frequency transformation has been concerned. How a three phase induction motor operates when rotor frequency is equal to stator frequency?
  • it will not operate
  • it will operate as induction motor only
  • it will operate as induction generator
  • it will operate in braking mode
Answer: it will not operate
Explaination:
as the rotor and stator
Q7 | and the rotor current I2 are zero at                    
  • ns
  • 2ns
  • zero
  • slip of 50%
Answer: ns
Explaination:
the rotor emf and current are zero at the speed of synchronous speed of the machine.
Q8 | If use auto transformer method starting to start an induction motor to replace star-delta method, then the required tapping on the transformer will be                    
  • 57.73%
  • 86.7%
  • 57%
  • 66.66%
Answer: 57.73%
Explaination:
k = 1/1.73 = 57.73%.
Q9 | The starting method for a 3-phase squirrel-cage induction motor which is inferior in view of poor starting torque per ampere of line current drawn is?
  • series-inductor method of starting
  • direct-on-line starting
  • auto-transformer method
  • star-delta method
Answer: series-inductor method of starting
Explaination:
due to inductor method, reactance increases and the starting torque decreases.
Q10 | volts, I = 200 A, and the cross-sectional area of the weld bead is 30 mm2. Estimate the welding speed if the workpiece and electrode are made of (a) aluminum, (b) carbon steel, and (c) titanium. Use an efficiency of 75%.
  • 35 mm/s
  • 34.5 mm/s
  • 36 mm/s
  • 46 mm/s
Answer: 34.5 mm/s
Explaination:
for aluminum, the specific energy required is u = 2.9 j/mm3 therefore,
Q11 | Upon which of the following parameters does the current intensity in arc welding depend?
  • stability of arc
  • electrode diameter
  • gap between the electrode and parent metals
  • thickness of parent metals
Answer: electrode diameter
Explaination:
electrodes for consumable arc- welding processes are classified according to the following properties:
Q12 | In which of the following welding processes we use two non-consumable electrodes?
  • mig
  • tig
  • atomic hydrogen
  • submerged arc
Answer: atomic hydrogen
Explaination:
non consumable electrodes are the ones that are not consumed during the process of welding. gtaw (gas tungsten arc welding)/tig (tungsten inert gas welding), ahw (atomic hydrogen welding), caw (carbon arc welding) processes use non-consumable electrodes.
Q13 | Which of the following brazing process is good for mass scale joining?
  • furnace
  • induction
  • dip
  • torch
Answer: furnace
Explaination:
furnace brazing is a semi- automatic used widely in industries and are best suited to large scale production operations.
Q14 | For grey cast iron, which of the following welding methods is preferable?
  • mig
  • submerged arc
  • gas flame
  • electric arc
Answer: mig
Explaination:
as the percentage of carbon in grey cast iron is less, therefore mig welding is preferable.
Q15 | Due to which of the following reasons, flux is not used in atomic hydrogen welding?
  • the burning hydrogen shields the molten metal
  • two electrodes are coated which gradually release the flux
  • the filler rod is coated with flux
  • one of the two electrodes is coated which releases the flux
Answer: the burning hydrogen shields the molten metal
Explaination:
separate flux/ shielding gas is not required in atomic hydrogen welding. the
Q16 | In resistance welding, between the electrodes, the nature of current and voltage parameters being used?
  • high current, high voltage
  • low current, high voltage
  • low current, low voltage
  • high current, low voltage
Answer: high current, low voltage
Explaination:
high current produces more heat. when we use a low voltage power source, it allows a welder to have some reasonable over the small lighting bolts we use to fuse metal together.
Q17 | Which of the following welding process in which heat is produced for welding by a chemical reaction?
  • resisting welding
  • thermit welding
  • forge welding
  • gas welding
Answer: thermit welding
Explaination:
the thermite process is a chemical reaction in which a metal oxide (preferably molten) is displaced by another molten metal which is more reactive than the metal in the metal oxide, releasing a lot of heat. example:
Q18 | The maximum diameter of electrodes being used in submerged arc welding?
  • 30 mm
  • 20 mm
  • 15 mm
  • 10 mm
Answer: 10 mm
Explaination:
a consumable electrode can be used by the submerged arc welding which is a loop of bare round wire with 1.5 mm to 10 mm diameter. it can be fed routinely throughout the welding gun, and the submerged arc welding electrode composition depends on the welded material.
Q19 | The coating material used for the electrode is termed as?
  • flux
  • slag
  • protective layer
  • deoxidiser
Answer: flux
Explaination:
flux is a substance used to prevent the formation of oxides and the other unwanted contaminations, or to dissolve them and facilitate removal. during welding the flux melts and becomes a liquid slag,
Q20 | Which of the following gases are used in Tungsten inert gas welding?
  • helium and neon
  • hydrogen and oxygen
  • argon and helium
  • carbon dioxide and hydrogen
Answer: argon and helium
Explaination:
in the tig welding process the arc is formed between a pointed tungsten electrode and the workpiece in an inert atmosphere of argon or helium.
Q21 | Which of the following materials necessitates preheating in welding?
  • copper
  • aluminium
  • cast iron
  • stainless steel
Answer: cast iron
Explaination:
as the weldability of cast iron usually decreases as the amount of free carbon in cast iron increases, so it is preheated to a dull red and then welded.
Q22 | Which of the following is also called “gas welding”?
  • oxy fuel gas welding
  • metallic welding
  • arc welding
  • fuel gas welding
Answer: oxy fuel gas welding
Explaination:
gas welding is also known as oxy fuel gas welding. in gas welding, fuel gases are used to generate high amount of heat and melt the metal.
Q23 | How many types of flames are there in welding?
  • 1
  • 2
  • 3
  • 4
Answer: 3
Explaination:
there are three basic flame types: neutral (balanced), excess acetylene (carburizing), and excess oxygen (oxidizing) as shown below.
Q24 | In which of the following type of flame, oxygen is in excess proportion with acetylene?
  • neutral flame
  • oxidizing flame
  • carburizing flame
  • both oxidizing flame and carburizing flame
Answer: oxidizing flame
Explaination:
oxidizing welding flames are produced when slightly more than one volume of oxygen is mixed with one volume of acetylene. oxidizing welding flames are commonly used to weld zinc, copper, manganese steel, cast iron, etc.
Q25 | In which of the following type of flame, oxygen is deficient in proportion with acetylene?
  • neutral flame
  • oxidizing flame
  • carburizing flame
  • both oxidizing flame and carburizing flame
Answer: carburizing flame
Explaination:
the carburizing flame has excess acetylene then oxygen. reducing flame is used for the welding of low carbon and alloy steel.
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