Manual metal arc welding is to be used for welding two plates each measuring $$800 \times 200 \times 19mm.$$ Given that
Length of weld $$\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,\,$$$$:180mm$$
Length of electrode$$\,\,\,\,\,\,\,\,\,\,\,$$ $$:450mm$$
Stub length$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,\,\,$$ $$:50mm$$
Diameter of electrode $$\,\,\,\,\,$$ $$:3mm$$
Weld reinforcement area $$:10\% $$
Spatter and other losses $$:15\% $$
Root gap $$=$$ land $$=$$ $$2mm$$
Angle of groove$$\,\,\,\,\,\,\,\,\,\,\,$$$$\,\,\,\,\,\,\,\,\,$$ $$:{60^ \circ }$$
Estimate the required number of electrodes for the weld.

An arc welding $$DC$$ power source has a linear power source characteristic with open circuit voltage $${V_O} = \,\,80$$ volts and short circuit current $${{\rm I}_S} = 1000amps.$$ The voltage-length characteristic of the arc is given by $$V=20+4L$$ volts where $$L$$ is the arc length in $$mm,$$ calculate the optimum length of arc for obtaining maximum arc power at welding. What voltage and current setting should be done on the power source for maximum arc power.