A $$DC$$ welding power source has a linear voltage-current $$(V$$-$$I)$$ characteristic with open circuit voltage of $$80V$$ and a short circuit current of $$300A.$$ For maximum arc power, the current (in Amperes) should be set as _______________

In a slab rolling operation, the maximum thickness reduction $$\left( {\Delta {h_{\max }}} \right)$$ is given by $$\Delta {h_{\max }} = {\mu ^2}R,$$ where $$R$$ is the radius of the roll and $$\mu $$ is the coefficient of friction between the roll and the sheet. If $$\mu = 0.1,$$ the maximum angle subtended by the deformation zone at the center of the roll (bit angle in degrees) is ____________

Under certain cutting conditions, doubling the cutting speed reduces the tool life to $${\left( {{1 \over {16}}} \right)^{th}}$$ of the original. Taylor’s tool life index $$(n)$$ for this tool workpiece combination will be ______________

An orthogonal turning operation is carried out under the following conditions; rake angle $$ = {5^ \circ },$$ spindle rotational speed $$=400$$ $$rpm,$$ axial feed $$=0.4$$ $$m/min$$ and radial depth of $$cut = 5mm$$. The chip thickness, $${t_c},$$ is found to be $$3mm.$$ The shear angle (in degrees) in this turning process is ________________