During gas welding of copper sheets a neutral flame was used consuming $$8$$ liters of acetylene. But the weld was found to be defective. So it was re-welded using an oxidizing flame. The likely consumption of oxygen in liters will be

The voltage-arc length characteristics of a power source is $$V=20+40L,$$ where $$V=$$ operating voltage in volts and $$L=$$ arc length in $$cm.$$ The open circuit voltage and short circuit current for arc lengths ranging from $$3$$ to $$5mm$$ and current from $$400$$ to $$500$$ amps during welding operation are

In a cutting test with $$0.3mm$$ flank wear as tool failure criterion, a tool life of $$10min$$ was obtained at a cutting velocity of $$20m/min.$$ Taking tool life exponrent as $$0.25,$$ the tool life in minutes at $$40m/min$$ of cutting velocity will be