With reference to electric arc welding:

(a) Draw a labeled sectional sketch of a satisfactory butt weld. (4)

(b) Briefly define the following defects that may occur and how they may have been caused: (12)

(i) Under cut

(ii) Splatter

(iii) Inclusion

(iv) Blow hole

(v) Incomplete root penetration

(vi) Lack of fusion