64. Pick up the incorrect statement for: A.C. arc welding always employs coated electrodes, because it
A.Has high efficiency and low splatter
B.Uses less input current
C.Is safest for operator
D.Has low leakage loss
65. In reverse polarity welding
A.Electrode holder is connected to the negative and work to positive
B.Electrode holder is connected to the positive and work to negative
C.Work is positive and holder is earthed
D.Holder is positive and work is earthed
66. Pick up the incorrect statement for: Coatings on electrodes are used to produce gas shields to protect the weld from atmosphere. The coating consists of
A.Flux and slagging materials like titanium oxide and calcium fluoride
B.Stabilisers to prevent splattering
C.Titanium oxide or potassium compounds to increase the melting rate, and ferro-manganese as a deoxidiser
D.Molasses as binder
67. The temperature of the plasma torch is of the order of
A.1000°C
B.5000°C
C.10,000°C
D.33,000°C
68. Following equipment is used for arc welding a material by carbon electrode
A.A.C. welding set
B.Rectifier
C.Motor generator
D.D.C. welding set with straight polarity
69. The strength of a properly welded joint as compared to base metal would be
A.Same
B.More
C.Less
D.Unpredictable
70. The advantages of electroslag welding are
A.Ability to weld metals of great thickness in a single pass without calling for joint preparation
B.Little distortion and good stress distribution across the weld
C.Protection from contamination
D.All of the above
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