16. Helium produces which of the following?
(a) Deeper penetration
(b) Faster welding speeds
(c) Narrower heat affected zone in base metal
(d) All of the above
17. Due to which of the following reasons aluminium is difficult to weld?
(a) It has an oxide coating
(b) It conducts away heat very rapidly
(c) Both (a) and (b)
(d) None of the above
18. Welding leads have
(a) high flexibility
(b) high current handling capacity
(c) both (a) and (b)
(d) none of the above
19. Air craft body is
(a) spot welded
(b) gas welded
(c) seam welded
(d) riveted
20. For arc welding, current range is usually
(a) 10 to 15 A
(b) 30 to 40 A
(c) 50 to 100 A
(d) 100 to 350 A
21. Spot welding is used for
(a) thin metal sheets
(b) rough and irregular surfaces
(c) costings only
(d) thick sections
22. Galvanising is a process of applying a layer of
(a) aluminium
(b) lead
(c) copper
(d) zinc
23. A seamless pipe has
(a) steam welded joint
(b) spot welded joint
(c) arc welded joint
(d) no joint
24. Motor-generator set for D.C. arc welding has generator of
(a) series type
(b) shunt type
(c) differentially compound type
(d) level compound type
25. Plain and butt welds may be used on materials upto thickness of nearly
(a) 5 mm
(b) 10 mm
(c) 25 mm
(d) 50 mm
26. In argon arc welding argon is used as a
(a) flux
(b) source of heat
(c) agent for heat transfer
(d) shield to protect the work from oxidation
27. During arc welding as the thickness of the metal to be welded increases
(a) current should decrease, the voltage should increase
(b) current should increase, voltage remaining the same
(c) current should increase, the voltage should decrease
(d) voltage should increase, current-remaining the same
28. In D.C. arc welding
(a) electrode is made positive and workpiece negative
(b) electrode is made negative and workpiece positive
(c) both electrodes, as well as workpiece, are made positive
(d) both electrodes, as well as workpiece, are made negative
29. The purpose of coating on arc welding electrodes is to
(a) stabilise the arc
(b) provide a protecting atmosphere
(c) provide slag to protect the molten metal
(d) all of the above
30. 50 percent duty cycle of a welding machine means
(a) machine input is 50 percent of rated input
(b) machine efficiency is 50 percent
(c) machine works on 50 percent output
(d) machine works for 5 minutes in a duration of 10 minutes