Fundamental of Welding Science and Technology NPTEL ANSWERS : WEEK 4

Week 4: Assignment 4

ANSWERS WEEK 5

An increase in radial pressure gradient dominates which of the following factors:

 Fusion depth decreases

 Fusion depth increases

 Constricts the arc

 Diverges the arc column

C

1 point

If the arcing time is 3 min, then duty cycle of welding machine as per the European standard is

 10%

 30%

 60%

 80%

C

1 point

Increased arc blow results in:

 Steady arc

 Low spatter

 Poor weld bead appearance

 All of these

D

1 point

Which of the following (s) is (are) an arc initiation process:

 Scratching method

 Taping method

 Both (a) and (b)

 None of these

C

1 point

Arc blow can be minimized by:

 Increase in traverse speed

 Using long arc

 Superimposing counter-acting longitudinal magnetic field

 Larger diameter electrode

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1 point

In welding, stable arc signifies as:

 Uniform and steady arc

 Uniform and unsteady arc

 Non-uniform and steady arc

 Non-uniform and unsteady arc

A

1 point

Consider the following statements:

        1. In arc welding 65 % to 75 % heat is generated at anode.

        2. Duty cycle in case of arc welding is the cycle of complete welding of workpiece from the beginning.

        3. Arc blow is more common with DC welding.

Which of the statements are correct?

 1, 2 and 3

 1 and 2

 2 and 3

 1 and 3

D

1 point

For a particular condition if the welding speed decreases, then:

 Arc blow increases

 Deflection of arc decreases

 Deflection of arc increases

 Arc blow decreases

D

1 point

Which force is responsible for rotating arc?

 Asymmetric radial force

 High velocity gas jet force

 Surface tension force

 Lorentz force

A

1 point

In welding, DCEP signifies:

 Direct current electric positive

 Direct current electrode positive

 Direct current electric pulse

 Direct current electrode pulse

B

1 point

Welding voltage across the arc coloumn can be expressed as V = A + B*L; where A denotes:

 A: Voltage drop taking place across anode and cathode drop region

 A: Voltage drop taking place across cathode drop region

 A: Voltage drop taking place across anode drop region

 A: Voltage drop along arc gap

A