With reference to electric arc welding:

(a) Draw a labeled sectional sketch of a satisfactory butt weld. (5)

(b) Briefly describe the cause of the following defects in welding:

(i) Under cut (1)

(i) Splatter (1)

(iii) Inclusion (1)

(iv) Blow hole (1)

(v) Incomplete root penetration (1)

(vi) Lack of fusion (1)

(c) Why is alternating current generally more popular than direct current for metal arc welding? (5)