NPTELFundamental of Welding Science and Technology: Week 6
NPTELFundamental of Welding Science and Technology: Week 7
NPTELFundamental of Welding Science and Technology: Week 8
Fundamental of Welding Science and Technology: Week 6
1) Oxidizing flame requires flux except for welding which of the following metals:
a)
b)
c)Brass
d)Zinc, lead
ANSWER:c)Brass
2)Which of the following flame is the hottest?
a)Reducing flame
b)Neutral flame
c)Oxidizing flame
d)
ANSWER:c)Oxidizing flame
3)An acetylene/oxygen flame burns at ___ °C.
a)2,250
b)2,526
c)3,073
d)
ANSWER:d)
4)In oxygen/acetylene welding for the complete combustion of C2H2:
a)1/5th proportion of the O2 comes from the cylinder
b)2/5th proportion of the O2 comes from the cylinder
c)3/5th proportion of the O2 comes from the cylinder
d)5/5th proportion of the O2 comes from the cylinder
ANSWER:b)2/5th proportion of the O2 comes from the cylinder
5)With the decrease of electrode extension:
a)Electrical resistance decreases
b)Bead width increases
c)More forceful arc
d)All three options (a, b, and c) are correct
ANSWER:d)All three options (a, b, and c) are correct
6)Effect of welding speed (w) on melting efficiency?
a)With increase of w, melting efficiency increase
b)With decrease of w, melting efficiency increase
c)W has no effect on melting efficiency
d)All of these
ANSWER:a)With increase of w, melting efficiency increase
7)Increase in welding current tends to cause:
a)
b)
c)More reinforcement
d)
ANSWER:a)
8)In a DC arc welding operation, the voltage-arc length characteristic was obtained as Varc = 20 + 5*l, where the arc length l was varied between 5 mm and 7 mm. Here Varc denotes the arc voltage in Volts. The arc current was varied from 400 A to 500 A. Assuming linear power source characteristic, the open circuit voltage and the short circuit current for the welding operation are:
a)
b)75 V, 750 A
c)95 V, 950 A
d)150 V, 1500 A
ANSWER:c)95 V, 950 A
9)In case of arc welding of steel with a potential of 20 V and current of 200 A, the travel speed is 5 mm/s and the cross-sectional area of the joint is 20 mm^2. The heat required for melting steel may be taken as 10 J/mm^3 and heat transfer efficiency as 0.85. The melting efficiency will be nearly:
a)18 %
b)
c)36 %
d)42 %
ANSWER:b)
10)A direct current welding machine with a linear power source characteristic provides open circuit voltage of 80 V and short circuit current of 800 A. During welding the machine, the measured arc current is 500 A corresponding to an arc length of 5.0 mm and the measured arc current is 460 A corresponding to an arc length of 7.0 mm. the linear voltage (E)-arc length (L) characteristic of the welding arc can be given as (where E is in volt and L is in mm)?
a)E = 80 + 8L
b)E = 80 + 2L
c)
d)
ANSWER:d)
CRITERIA TO GET A CERTIFICATE
Average assignment score = 25% of average of best 8 assignments out of the total 12 assignments given in the course.
Exam score = 75% of the proctored certification exam score out of 100
Final score = Average assignment score + Exam score
YOU WILL BE ELIGIBLE FOR A CERTIFICATE ONLY IF AVERAGE ASSIGNMENT SCORE >=10/25 AND EXAM SCORE >= 30/75. If one of the 2 criteria is not met, you will not get the certificate even if the Final score >= 40/100.
Disclaimer:
The answers provided in this blogpost are for reference only and should not be used as a substitute for your own research and understanding of the subject matter. The answers have been researched and compiled to the best of our knowledge, but we cannot guarantee their accuracy or completeness. We strongly advise that you use this information as a starting point for your own research and not as the sole basis for your work. Please use your own discretion and always consult your instructor or professor for guidance.
