Two mild steel plates of similar thickness, in butt-joint configuration, are welded by gas tungsten arc welding process using the following welding parameters.

$$ \begin{array}{|l|l|} \hline \text { Welding voltage } & 20 \mathrm{~V} \\ \hline \text { Welding current } & 150 \mathrm{~A} \\ \hline \text { Welding speed } & 5 \mathrm{~mm} / \mathrm{s} \\ \hline \end{array} $$

A filler wire of the same mild steel material having 3 mm diameter is used in this welding process. The filler wire feed rate is selected such that the final weld bead is composed of 60% volume of filler and 40% volume of plate material. The heat required to melt the mild steel material is 10 J/mm3. The heat transfer factor is 0.7 and melting factor is 0.6. The feed rate of the filler wire is __________ mm/s (round off to one decimal place).

The voltage - length characteristic of a direct current arc in an arc welding process is $$V=$$ $$(100+40l),$$ where $$l$$ is the length of the arc in $$mm$$ and $$V$$ is arc voltage in volts. During a welding operation, the arc length varies between $$1$$ and $$2$$ $$mm$$ and the welding current is the range $$200$$-$$250A$$. Assuming a linear power source, the short circuit current is _____________$$A.$$

Spot welding of two steel sheets each $$2$$ $$mm$$ thick carried out successfully by passing $$4$$ $$kA$$ of current for $$0.2$$ seconds through the electrodes. The resulting weld nugget formed between the sheets is $$5$$ $$mm$$ in diameter. Assuming cylindrical shape for the nugget, the thickness of the nugget is ______________$$mm.$$

During a $$TIG$$ welding process, the arc current and arc voltage were $$50$$ $$A$$ and $$60$$ $$V,$$ respectively, when the welding speed was $$150$$ $$mm/min.$$ In another process, the $$TIG$$ welding is carried out at a welding speed of $$120mm/min$$ at the same arc welding voltage and heat input to the material so that weld quality remains the same. The welding current (in $$A$$) for this process is