1
GATE PI 2008
+2
-0.6
Oil is being pumped through a straight pipe, the pipe length, diameter and volumetric flow rate are all doubled in a new arrangement. The pipe friction factor, however, remains constant. The ratio of pipe frictional losses in the new arrangement to that in the original configuration would be
A
$${1 \over 4}$$
B
$${1 \over 2}$$
C
$$2$$
D
$$4$$
2
GATE PI 2008
+2
-0.6
Two pipes of inner diameter $$100mm$$ and outer diameter $$110mm$$ each are joined by flash butt welding using $$30V$$ power supply. At the interface, $$1mm$$ of material melts from each pipe which has a resistance of $$42$$ Ohms.If the unit melt energy is $$64.4$$ $$MJ/{m^3}$$, then time required for welding (in $$S$$) is
A
$$1$$
B
$$5$$
C
$$10$$
D
$$20$$
3
GATE PI 2008
+2
-0.6
Aluminium strips of $$2mm$$ thickness are joined together by resistance spot welding process by applying an electric current $$6000$$$$A$$ for $$0.15sec$$. The heat required for melting aluminium is $$2.9J/m{m^3}.$$ The diameter and thickness of the weld nugget are found to be $$5$$ $$mm$$ and $$2.5mm$$ respectively. Assuming the electrical resistance to be $$75$$ micro-ohms, the percentage of total energy utilized in forming the weld nugget is
A
$$28$$
B
$$35$$
C
$$65$$
D
$$72$$
4
GATE PI 2008
+2
-0.6
Which of the following powders should be fed for effective oxy-fuel cutting of stainless steel
A
Steel
B
Aluminium
C
Copper
D
Ceramic
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