A $$900$$ $$mm$$ long steel plate is welded by manual metal arc welding process using welding current of $$150$$ $$A,$$ arc voltage of $$20$$ $$V$$ and welding speed of $$300$$ $$mm/min.$$ If the process efficiency of is $$0.8$$ and surface resistance is $$36$$ micro-ohm, the heat input will be

The cold cracking susceptibility of the heat affected zone in an arc weld is influenced by
$$P.$$ Entraped hydrogen,
$$Q.$$ Residual stresses
$$R.$$ Marternsitic transformation
$$S.$$ Slag inclusion

In spot pulsed laser welding of aluminium plates (density $$ = 2700kg/{m^3},$$ specific heat $$=896J/kg,$$ melting temp $$=933K,$$ latent heat of melting $$ = 398\,\,kJ/kg)$$ at a temp of $${30^ \circ }C,$$ pulse with energy of $$0.5J$$ is focused onto an area of $$0.05m{m^2}.$$ If the entire energy is coupled into the material, what will be the depth of weld assuming the $$CS$$ area of the weld is circular and is uniform throughout its depth and only heat conduction in the direction of penetration