A casting of $$200\,\,mm\,\, \times \,\,100\,\,mm \times 70\,\,mm$$ size solidifies in ten minutes. Estimate solidification time for a $$200\,\,mm\,\, \times \,\,100\,\,mm \times 10\,\,mm$$ casting under similar conditions?

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