Fundamental of Welding Science and Technology NPTEL, WEEK-3

 Fundamental of Welding Science and Technology

Week 3: Assignment 

1 point

Which one of the following gas atmosphere is readily used to promote thermionic emission more readily due to its least ionization potential?

 He

 Ar

 N2

 CO2

C

1 point

Which one of the factors plays a key role in exhibiting thermionic emission rapidly?

 Concentration of electron decrease, absolute temperature decrease

 Current density increase, absolute temperature increase

 Current density and absolute temperature remain same

 None of these

B

1 point

Variable speed feed drive system compensate variation in arc length by:

 Increase or decrease of electrode feed rate

 Self-regulation of arc length characteristics

 Sensing the fluctuation with the help of diode

 None of these

A

1 point

For maintaining arc length constant speed feed drive system is used with _____ power supply

 CV

 CC

 Dynamic characteritics

 None of these

A

1 point

Pulsed mode of power supply provides:

 AC along with pulsed mode

 DC along with pulsed mode

 AC

 DC

NOT AVAILABLE :B

1 point

Which statement is true for dynamic characteristics of power sources?

 Inductor is used to increase the current which provides better melting rate

 Transistor is used to increase the current which provides better melting rate

 Inductor is used to decrease the current which provides stability of arc

 Thyristor is used to decrease the current which provides stability of arc

C

1 point

Which one of the welding process uses combined characteristics of power source?

 GMAW-P

 ESW

 PAW

 EGW

D

1 point

Which pair of the welding process uses constant voltage power source characteristics?

 GTAW and SMAW

 SMAW and PAW

 MIG and FCAW

 None of these

C

1 point

In which of the welding processes constant current power supply is used?

 Plasma arc welding

 Metal Inert gas welding

 Shielded metal arc welding

 Laser welding

C

1 point

Arc length-voltage characteristics for a welding operation is given by V = 20 + 4 L. If the arc length varies between 4 mm to 6 mm and welding current varies between 450 A to 550 A. Assuring linear power source, calculate (a) Open circuit voltage (b) Short circuit current

 50 V and 700 A

 60 V and 800 A

 70 V and 900 A

 80 V and 1000 A

D (Not Sure)