Deck 10: Three Phase Induction Motors and Welding Processes

Question 1

A three phase induction motor is sometimes called 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 greater than stator frequency?

A)rotor will be driven against rmf
B)rotor will be driven in direction of rmf
C)no emf will be induced
D)the losses will be maximum

Answer 1

rotor will be driven against rmf

Question 2

A three phase induction motor is sometimes called 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 less than stator frequency?

A)it operates as induction motor
B)emf is induced in rotor
C)rmf will rotate at synchronous speed
D)all of the mentioned

Answer 2

all of the mentioned

Question 3

A three phase induction motor is sometimes called a generalized transformer in so far as voltage and frequency transformation has been concerned. Then the rotor emf E2 and the rotor current I2 are zero at_______________    

A)ns
B)2ns
C)zero
D)slip of 50%

Answer 3

ns

Question 4

Consider a situation in which a welding operation is being performed with V = 20 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%.

A)35 mm/s
B)34.5 mm/s
C)36 mm/s
D)46 mm/s

Question 5

In arc welding, arc is created between the electrode and work by?

A)contact resistance
B)flow of voltage
C)flow of current
D)electrical energy

Question 6

The coating material used for the electrode is termed as?

A)flux
B)slag
C)protective layer
D)deoxidiser

Question 7

Which of the following welding process in which two pieces to be joined are overlapped and placed between two pointed electrodes?

A)seam welding
B)resistance welding
C)projection welding
D)spot welding

Question 8

In which of the following type of flame, oxygen is of same proportion with acetylene?

A)neutral flame
B)oxidizing flame
C)carburizing flame
D)both oxidizing flame and carburizing flame

Question 9

If the open circuit voltage is 60 volt and the short circuit current is 20 amperes. Then determine the voltage required for welding if the current required during welding is 10 amperes?

A)30 v
B)60 v
C)20 v
D)40 v

Question 10

How does the arc voltage V depends upon the length of arc L?

A)v = f(l)
B)v = 1/f(l)
C)v = f(l2)
D)v = f(?l)

Question 11

What is the only difference between Plasma arc welding and TIG welding?

A)flux is not used
B)construction of torch is different
C)gas is not used
D)tungsten electrode is not used

Question 12

In plasma arc welding the gas is?

A)ionized
B)heated
C)magnetized
D)vaporized

Question 13

If the total efficiency is 0.35 in arc welding. Then what is the welding speed in mm/sec if the cross-sectional area is 5mm2, welding power is 2 kW and the heat required in melting the metal is 100 J/mm3.

A)1.4
B)14
C)1400
D)140

Question 14

Which of the following inert gas is used with DC power supply only?

A)argon
B)helium
C)CO₂
D)nitrogen

Question 15

Which kind of resistance is experienced in upset butt welding?

A)electric resistance
B)magnetic resistance
C)thermal resistance
D)air resistance

Question 16

How are the metals to be welded connected to each other in spot welding?

A)electric contact
B)magnetic field
C)mechanical pressure
D)direct contact

Question 17

Up to what thickness, can steel be welded using spot welding process?

A)10 mm
B)11 mm
C)12 mm
D)13 mm

Question 18

In flash butt welding, the forced out metal is called flash.

Question 19

In friction welding process, materials are joined by__________motion between materials.

A)rectilinear
B)rubbing
C)translatory
D)brownian

Question 20

All metallic engineering materials which are__________can be friction welded.

A)soft
B)weldable
C)forgeable
D)metamaterials

Question 21

Friction welding is__________process.

A)costly
B)cost saving
C)time consuming
D)highly material selective

Question 22

Friction welding produces quality joints, with a 100%__________weld.

A)lap joint
B)tee-joint
C)butt joint
D)edge joint

Question 23

In inertia friction welding__________  energy of welding machine is used.

A)electrical
B)potential
C)rotational
D)frictional

Question 24

In inertia friction welding, one workpiece is connected to__________

A)flywheel
B)the pin tool
C)rotor
D)generator

Question 25

Which of the following defects occur when weld metal layer fails to fuse together?

A)inclusion of slag
B)inadequate penetration
C)incomplete fusion
D)porosity